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11 1&2 C2 Mock Exam Revision Questions – Higher C2.1&C2.2 Structure and properties Q1. This question is about the structure of atoms. (a) Choose words from the list to complete the sentences below. electrons ions neutrons protons In an atom, the particles with a negative charge are called ..................................... Particles in the nucleus with no charge are called ..................................................... An atom has no overall charge because is has the same number of electrons and .................................................................................................................................... (3) (b) Two isotopes of the element carbon are: 12 C 6 14 and C 6 Complete the table of information for these two isotopes. ATOMIC NUMBER MASS NUMBER NUMBER OF PROTONS 12 6 Isotope 12 C 6 6 Isotope 12 C 6 6 NUMBER OF NEUTRONS 6 6 (2) Q2. This question is about oxygen atoms. The periodic table on the Data Sheet may help you to answer this question. (a) (i) Oxygen atoms have 8 electrons. Complete the diagram to represent the arrangement of electrons in an oxygen atom. Use crosses (×) to represent the electrons. (1) (ii) Name the part of the oxygen atom that is labelled A on the diagram. ........................................................................................................................... (1) (b) Two isotopes of oxygen are oxygen-16 and oxygen-18. 16 18 O O 8 8 oxygen-16 oxygen-18 Explain, in terms of particles, how the nucleus of an oxygen-18 atom is different from the nucleus of an oxygen-16 atom. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q3. The two carbon atoms represented below are isotopes. ISOTOPE 1 14 ISOTOPE 2 mass number C 6 (a) proton number 12 C 6 Describe two ways in which the isotopes are similar. ..................................................................................................................................... ..................................................................................................................................... (2) (b) Describe as fully as you can one way in which they are different. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q4. The picture shows sodium reacting with chlorine. The reaction forms sodium chloride. (a) Use words from the box to answer the questions. compound element hydrocarbon mixture Which word best describes: (i) sodium ....................................................................... (1) (ii) sodium chloride? ........................................................ (1) (b) When sodium reacts with chlorine the sodium atoms change into sodium ions. The diagrams below represent a sodium atom and a sodium ion. Use the diagrams to help you explain how a sodium atom turns into a sodium ion. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (c) (i) The diagram below represents a chlorine atom. When chlorine reacts with sodium the chlorine forms negative chloride ions. Complete the diagram below to show the outer electrons in a chloride ion (Cl–). (1) (ii) Chloride ions are strongly attracted to sodium ions in sodium chloride. Explain why. ............................................................................................................... ............................................................................................................... (1) (Total 6 marks) Q5. Calcium and magnesium are elements. They are found in the Earth’s crust as compounds, often carbonates and sulphates. Magnesium is also found as its chloride. (a) Calcium and magnesium are in the same Group in the Periodic Table. State which Group this is. ..................................................................................................................................... (1) (b) Use the Data Sheet to help you to answer this question. (i) Write the chemical formula of magnesium chloride. ........................................................................................................................... (1) (ii) Name the type of bonding in magnesium chloride. ........................................................................................................................... (1) (Total 3 marks) Q6. The drawing shows a container of a compound called magnesium chloride. (i) How many elements are joined together to form magnesium chloride? .................................................................................................................................... (1) (ii) Magnesium chloride is an ionic compound. What are the names of its ions? ................................................. ions and ................................................. ions (1) (iii) How many negative ions are there in the formula for magnesium chloride? .................................................................................................................................... (1) (iv) Complete the sentence. Ions are atoms, or groups of atoms, which have lost or gained ......................................... . (1) (v) Suggest three properties which magnesium chloride has because it is an ionic compound. Property 1 ................................................................................................................... .................................................................................................................................... Property 2 .................................................................................................................. .................................................................................................................................... Property 3 .................................................................................................................. .................................................................................................................................... (3) (Total 7 marks) Q7. Sodium chloride is an ionic compound. (Total 2 marks) Q8. (a) Write a balanced symbol equation for the reaction between magnesium (Mg) and oxygen (O2) to form magnesium oxide (MgO). ..................................................................................................................................... (1) (b) The diagram shows the electronic structure of a magnesium atom. The atomic (proton) number of magnesium is 12. Magnesium atom Oxygen atom Draw a similar diagram to show the electronic structure of an oxygen atom. The atomic (proton) number of oxygen is 8. (1) (c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen. The diagram shows the electronic structure of an oxide ion. Oxide ion Magnesium ion Draw a similar diagram to show the electronic structure of a magnesium ion (1) (d) Magnesium oxide is a white solid with a high melting point. Explain how the ions are held together in solid magnesium oxide. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (e) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach. Complete the word equation for the reaction between magnesium oxide and hydrochloric acid. hydrochloric acid + magnesium oxide → ...................... + water. (1) (Total 6 marks) Q9. (a) (i) The diagram shows part of the ionic lattice of a sodium chloride crystal. Complete the spaces in the table to give information about both of the ions in this lattice. Name of ion Charge ..................................................... ..................................................... ..................................................... ..................................................... (2) (ii) When it is solid, sodium chloride will not conduct electricity. However, molten sodium chloride will conduct electricity. Explain this difference. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (iii) Complete the sentence. Sodium chloride conducts electricity when it is molten and when it is .......................................................................................................................... (1) (b) The symbol for a calcium atom can be shown like this: (i) What is the mass number of this atom? .......................................................................................................................... (1) (ii) What information is given by the mass number? .......................................................................................................................... .......................................................................................................................... (1) (c) Calcium burns in oxygen with a brick-red flame. The product is a white solid. It is calcium oxide and its formula is CaO. (i) Balance the chemical equation for the reaction. Ca(s) + O2(g) → CaO(s) (1) (ii) Describe, in terms of electrons, what happens to a calcium atom when it becomes a calcium ion. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (Total 10 marks) Q10. Atoms of calcium, phosphorus and fluorine are represented below, each with its mass number and proton number. (a) Use this information to complete the table. CALCIUM Number of protons in the nucleus 20 Number of neutrons in the nucleus 20 PHOSPHOROUS Number of electrons FLUORINE 9 16 15 9 (3) (b) Calcium and fluorine atoms can combine to form the compound calcium fluoride, CaF2. The fluoride ion is represented by F–. (i) Explain how the fluorine atom forms a fluoride ion. .......................................................................................................................... .......................................................................................................................... (2) (ii) How is the calcium ion represented? .......................................................................................................................... (2) (c) Phosphorus and fluorine form a covalent compound, phosphorus trifluoride. Complete the sentences below which are about this compound. Phosphorus trifluoride is made up of phosphorus and fluorine ................................ These are joined together by sharing pairs of ............................................... to form phosphorus trifluoride ........................................................ . (3) (d) (i) Sodium chloride, an ionic compound, has a high melting point whereas paraffin wax, a molecular compound, melts easily. Explain why. .......................................................................................................................... .......................................................................................................................... (2) (ii) Molten ionic compounds conduct electricity but molecular compounds are non-conductors, even when liquid. Explain why. .......................................................................................................................... .......................................................................................................................... (2) (Total 14 marks) Q11. The diagram represents a particle of methane. (a) What is the formula of methane? ............................................................................... (1) (b) Choose a word from the box to answer the question. atom ion molecule Which of the words best describes the methane particle shown in the diagram? ................................................. (1) (c) Choose a word from the box to answer the question. covalent ionic metallic What is the type of bonding shown in the diagram? .................................................. (1) (Total 3 marks) Q12. This barbecue burns propane gas. The diagram represents a propane molecule. (a) What is the formula of propane? ........................................................................................ (1) (b) (i) Draw a ring around the name of the particle represented by the symbols ○ and × in the diagram. electron neutron proton (1) (ii) Draw a ring around the type of bonding that holds the atoms together in a propane molecule. covalent ionic metallic (1) (c) Under high pressure in the cylinder propane is a liquid. Liquid propane evaporates easily to form a gas when the tap on the cylinder is opened. Draw a ring around the correct answer in each box to explain why propane evaporates easily. Propane has a high low boiling point because it consists of large small molecules. (1) (Total 4 marks) Q13. (a) The diagram represents an atom of nitrogen. (i) Use words from the box to label the diagram. electron neutron nucleus proton (2) (ii) Draw a ring around the mass number of this atom. 5 7 14 21 (1) (b) Nitrogen can react with hydrogen to make ammonia, NH3 . Which diagram, A, B, C or D, best represents an ammonia molecule? (1) (Total 4 marks) Q14. Diesel oil is obtained from crude oil. It can be used as a fuel for car engines. The diagram below represents a compound found in diesel oil. (a) What is the formula of this compound? ..................................................................................................................................... (1) (b) Each of the lines on the diagram above represents a covalent bond. What is a covalent bond? ..................................................................................................................................... ..................................................................................................................................... (2) (Total 3 marks) Q15. The hydrogen halides (hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide) are important chemicals. The diagram below represents a molecule of hydrogen chloride. (i) What type of particles are represented by the crosses (X)? ..................................................................................................................................... (1) (ii) What type of chemical bond holds the atoms in this molecule together? ..................................................................................................................................... (1) (iii) Would you expect hydrogen chloride to be a gas, a liquid or a solid, at room temperature and pressure? Explain your answer. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 5 marks) Q16. (i) Complete the drawing to show the electron structure of a hydrogen fluoride molecule. Draw electrons as dots or crosses. (1) (ii) Explain why hydrogen fluoride is a gas at room temperature. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 3 marks) Q17. This question is about giant structures. Diamond, graphite and silicon dioxide all have giant structures. (a) The diagrams show the structures of these three substances. Draw a line from each structure to its name. (2) (b) Complete the sentences using words from the box. (i) covalent four hard ionic shiny soft three two Diamond, graphite and silicon dioxide have high melting points because all the atoms in their structures are joined by strong ............................................... bonds. (1) (ii) In diamond each atom is joined to ............................................... other atoms. (1) (iii) Diamond can be used to make cutting tools because it has a rigid structure which makes it very ................................................ (1) (iv) In graphite each atom is joined to ............................................... other atoms. (1) (v) Graphite can be used to make pencils because it has a structure which makes it ................................................ (1) Q18. The diagram shows the structure of diamond. (a) To gain full marks for this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. Explain, as fully as you can, why diamond has a high melting point. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (b) The diagram below shows the outer electron shells of five carbon atoms in the giant lattice of diamond. Carbon atom C forms bonds with each of the carbon atoms W, X, Y and Z. Draw the positions of all the electrons in the outer shells of each of carbon atoms C, W, X, Y and Z. (3) (Total 6 marks) Q19. The diagram represents the structure of graphite. Use your knowledge and understanding of the structure of graphite to explain why graphite can be used: (a) in the ‘leads’ of pencils; .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (b) as an electrical conductor. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (Total 5 marks) Q20. The diagram shows a model of part of the giant lattice of a metal. (a) Name particles X and Y. X ..................................................... Y ..................................................... (2) (b) Explain, in terms of the giant structure above, why is it possible to bend a piece of metal. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks Q21. The extract below was taken from a leaflet on the uses of platinum. One of the uses described was in making electrodes for spark plugs in car engines. The spark plug produces the spark which ignites the fuel in the engine. Spark Plugs The electrodes in a spark plug have to conduct electricity very well. Since they project into the combustion chamber of the engine, they must also be able to withstand extremely high temperatures in a very corrosive atmosphere. Nickel-based plugs have been produced for many years. They only last a fairly short time. As the electrodes wear, combustion becomes less efficient and the petrol is not burnt completely. Platinum and other precious metals can now be used in spark plugs. These last much longer and are more efficient. This can help to reduce air pollution. The table below gives some information about platinum and nickel. (a) MELTING POINT (° C) BOILING POINT (° C) POSITION IN REACTIVITY SERIES COST (£/kg) nickel 1455 2920 Higher than gold 2.5 platinum 1769 4107 below gold 6110 Compare nickel and platinum for use in making the electrodes in spark plugs. A good answer should give advantages and disadvantages of each metal linking these to the properties of the metals. Marks will be given for the way in which you organise your answer. You will need a sheet of lined paper. (8) (b) (i) Describe the structure and bonding in metals. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) (ii) Explain why metals such as nickel and platinum are good conductors of electricity. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 13 marks) Q22. Metals and their alloys have many uses. (a) Dentists use a smart alloy to make braces that gently push teeth into the right position. What is meant by a smart alloy? .................................................................................................................................... (1) (b) Pure copper is made up of layers of copper atoms. Brass is an alloy of copper and zinc. Why are the physical properties of brass different from the physical properties of pure copper? .................................................................................................................................... .................................................................................................................................... (2) Q23. The hip joint between the femur and pelvis sometimes has to be replaced. Early hip replacement joints were made from stainless steel. Stainless steel is an alloy of iron, chromium and nickel. The diagram below represents the particles in stainless steel. (a) Use the particle diagram to complete the percentages of metals in this stainless steel. The first one has been done for you. Element Percentage (%) Iron, Fe 72 Chromium, Cr Nickel, Ni (2) (b) Pure iron is a relatively soft, metallic element. (i) Why is iron described as an element? ........................................................................................................................... (1) (ii) Suggest why pure iron would not be suitable for a hip replacement joint. ........................................................................................................................... ........................................................................................................................... (1) (iii) Use the particle diagram to help you to explain why stainless steel is harder than pure iron. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 6 marks) Q24. This picture shows a sword. The sword is about 3400 years old. It is made of an alloy called bronze. Bronze is made from copper and tin. Bronze made better swords than pure copper. This is because bronze is harder than pure copper. Explain why bronze is harder than pure copper. Your answer should include details of: • how the atoms are arranged in pure copper and bronze • why pure copper is relatively soft • why bronze is harder. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. (Total 4 marks) Q25. This drinks bottle is made of thermosoftening plastic. a) Explain why a thermosoftening plastic is flexible and melts easily. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. (2) b) Explain why a thermosetting plastic is rigid and does not melt when heated. ................................................................................................................................ ................................................................................................................................. ................................................................................................................................. (2) (Total 4 marks) Q26. Read the article and then answer the questions. Nanotennis! Tennis balls contain air under pressure, which gives them their bounce. Normal tennis balls are changed at regular intervals during tennis matches because they slowly lose some of the air. ‘Nanocoated’ tennis balls have a ‘nanosize’ layer of butyl rubber. This layer slows down the escape of air so that the ball does not lose its pressure as quickly. (a) What is the meaning of nanosize? ..................................................................................................................................... ..................................................................................................................................... (1) (b) Suggest why using ‘nanocoated’ tennis balls would be good for the environment. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 3 marks) Q27. Read this passage about metals. Metals are crystalline materials. The metal crystals are normally about 20 000 nm (nanometres) in diameter. The atoms inside these crystals are arranged in layers. A new nanoscience process produces nanocrystalline metals. Nanocrystalline metals are stronger and harder than normal metals. It is hoped that nanocrystalline metals can be used in hip replacements. The use of nanocrystalline metals should give people better hip replacements which last longer. (a) State why metals can be bent and hammered into different shapes. ..................................................................................................................................... ..................................................................................................................................... (1) (b) How is the size of the crystals in nanocrystalline metals different from the size of the crystals in normal metals? ..................................................................................................................................... ..................................................................................................................................... (1) (c) Hip joints are constantly moving when people walk. Suggest and explain why the hip replacement made of nanocrystalline metal should last longer than one made of normal metals. ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) M1. (a) electrons neutrons protons for 1 mark each 3 (b) mass number no. of neutrons 14 8 for 1 mark each 2 [5] M2. (a) (i) or 1 allow any arrangement of electrons on the shells accept o, x, - or e as representing electrons (ii) nucleus accept nucleus (protons plus neutrons) do not accept protons plus neutrons on its own allow nuclei / nucles / neucleus / phonetic spelling do not accept neutron 1 (b) it has 2 more neutrons or converse accept ‘it has more neutrons’ or ‘different number of neutrons’ for 1 mark ‘2 more protons / electrons + correct number of neutrons’ = max 1 mark or O-16 has 8 neutrons (1 mark)(*) O-18 has 10 neutrons (1 mark)(*) (*)if incorrectly calculated but shows more neutrons in 0-18 allow for 1 mark accept it has more particles or it has 2 more particles for 1 mark ignore any reference to charges just 2 more without reference to particles = 0 marks 2 [4] M3. (a) same number/six electrons; same number/six protons; react in same way not same element or both carbon any two for 1 mark each 2 (b) different number of neutrons gains 1 mark but or C has two more neutrons gains 1 mark different mass number or but two mass units bigger gains 2 marks C has 8 neutrons while gains 2 marks C has 6 neutrons 2 [4] M4. (a) (i) element 1 (ii) compound 1 (b) an / one electron from the sodium atom 1 is lost / transferred to form a sodium ion 1 (c) (i) 8 electrons drawn on outer energy level / shell 1 (ii) because oppositely charged ions attract each other or because chloride ions are negative and sodium ions are positive 1 [6] M5. (a) Group 2 / Alkaline Earth Metals for 1 mark 1 (b) (i) MgCl2/Mg2+ (Cl–)2 for 1 mark 1 (ii) ionic / electrovalent for 1 mark 1 M6. (i) two or 2 1 (ii) magnesium and chloride either order not positive / negative do not credit’chlorine’ accept Mg++ and Cldo not credit just Mg and Cl– accept cation(s) and anion(s) 1 (iii) 2 1 (iv) electrons accept charges 1 (v) any three from • (is a) giant structure/lattice structure • crystalline / hard accept just 'crystals(s)’ • high melting point / solid • high boiling point • conductor (of electricity) when dissolved in water or conductor (of electricity) when ions are free to move • conductor (of electricity) when molten • soluble in water 3 [7] M7. 8 electrons in outer shell accept anywhere in outer shell accept dots or crosses 1 negative sign outside bracket 1 [2] M8. (a) 2Mg + O2 → 2MgO accept correct multiples / fractions 1 (b) electrons do not need to be paired accept dots / circles / e instead of crosses do not allow 2.6 without diagram 1 (c) electrons do not need to be paired allow without bracket s/ must have the charge accept dots / circles / e instead of crosses ignore extra empty outer shells ignore nucleus do not allow [2.8]2+ without diagram 1 (d) oppositely charged (ions / atoms) allow positive and negative(ions / atoms) 1 (they) attract must be in correct context accept held by electrostatic forces ignore ionic bonding maximum 1 if they refer to intermolecular forces / attractions / covalent bonds 1 (e) magnesium chloride accept MgCl2 (if correctly written) 1 [6] M9. (a) (i) sodium........ positive or + both required 1 chloride... negative or – both required do not credit chlorine 1 (ii) ions not free (to move) in solid crystal / lattice ions are free to move when sodium chloride is molten 1 or ions are mobile do not credit when ions are molten allow 'particles' for ions (1) mark do not credit electrons etc 1 (iii) dissolved in water or in aqueous solution accept in solution accept in water or when a gas/ vapour or solid it will not 1 (b) (i) 40 1 (ii) (total) number of protons and neutrons (in the nucleus) 1 (c) (i) 2Ca + O2 -+ 2CaO accept any 2n : n : 2n ratio do not credit if any other change has been made 1 (ii) any two from electron(s) is / are lost from the outer shell / orbit / ring or from the shell furthest the nucleus or from the 4th shell two / both (electrons are lost) accept two electrons are lost for (2)marks accept both electrons are lost from the atom for (1) mark 2 [10] M10. (a) Calcium No of protons Phosphorus 15 No of neutrons No of electrons Fluorine 10 20 for 1 mark each 3 (b) (i) gain of electron(s) from (atoms) (of) calcium for 1 mark 2 (ii) Ca+ gains 1 mark but superscript only Ca2+ / Ca ++ gains 2 marks 2 (c) atoms electrons molecule(s) not compound each for 1 mark 3 (d) (i) ideas that • ionic – strong forces between ions • molecular – weak forces between molecules each for 1 mark 2 (ii) ideas that • ionic – ions/charged particles are free to move • molecular -molecules do not carry a charge each for 1 mark 2 [14] M11. (a) CH4 4 should be below halfway up H / tail of 4 below the dotted line 1 (b) molecule 1 (c) covalent 1 [3] M12. (a) C3H8 capital letters for symbols numbers must be halfway or lower down the element symbol allow H8C3 do not allow 3:8 or C3 and H8 1 (b) (i) electron 1 (ii) covalent 1 (c) low and small both for 1 mark 1 [4] M13. (a) (i) all three correct 2 marks one correct 1 mark 2 (ii) 14 1 (b) A 1 [4] M14. (a) C16 H34 for 1 mark 1 (b) electron gains 1 mark but shared electrons gains 2 marks 2 M15. (i) (ii) electrons for 1 mark covalent 1 1 for 1 mark (iii) made of small molecules: usually gas or liquid ) dependent on have low melting points ) having first have low boiling points ) point above forces between molecules are weak any 1 for 1 mark 3 [5] M16. (i) (ii) 1 weak forces accept weak bonds 1 between molecules / intermolecular reject intramolecular 1 [3] M17. (a) all three lines correct gains 2 marks one or two correct gains 1 mark if there are more than 3 lines then lose mark for each extra line 2 (b) (i) covalent 1 (ii) four 1 (iii) hard 1 (iv) three 1 (v) soft 1 (c) carbon accept C 1 [8] M18. (a) Quality of written communication: All scientific words used correctly (covalent, bonds, atoms) 1 any two from • large numbers of covalent bonds allow giant lattice / structure • between atoms do not accept between molecules • (covalent) bonds strong accept need much energy to break 2 (b) each carbon has 4 electrons 1 one shared pair 1 four shared pairs 1 [6] M19. (a) made of layers of carbon atoms weak forces of attraction between layers (owtte) / weak vertical bonds i.e. candidate refers to the diagram layers can slide over each other layers peel off each for 1 mark (b) because there are electrons which are free (to move) reason for free electrons / each carbon atom has 3 covalent bonds each for 1 mark to max 5 [5] M20. (a) X – (metal) atom / ion 1 Y – electron 1 (b) free electrons or electrons move 1 (allow metal) atoms / ions to slide over each other OR bonding non - directional for 2 marks 1 [4] M21. (a) 8 marks Particularly well structured answer with most points mentioned. 7-6 marks Well structured answer. The two metals will have been compared rather than simply listing advantages/disadvantages. Most of the advantages and disadvantages of each metal have been mentioned. 5-3 marks Some structure to the answer. An attempt to compare the metals by giving some advantages and disadvantages. 2-1 marks Little structure or attempt to compare. Marks gained by listing a few advantages or disadvantages. Advantages of Nickel: Relatively low cost which makes the sparking plugs cheaper to produce. Quite high melting point which is needed because the temperature in the engine is very high. Good conductor of electricity needed to carry electricity into combustion chamber to produce spark. Disadvantages of Nickel: Subject to corrosion in engine which means they only last a short time because nickel is higher in reactivity than platinum. Idea that this leads to reduced efficiency, unburnt petrol and air pollution. Advantages of Platinum: Less susceptible to corrosion (not corroded) because platinum is very low in reactivity. Idea that this improves efficiency and reduces pollution.Higher melting point than nickel to withstand the high temperatures in the combustion chamber. Last a lot longer than nickel electrodes due to low reactivity. (Sensible extension here could be longer service intervals etc.)Good conductor of electricity as for nickel. Extension here could be linked to the idea that the conductivity does not deteriorate as quickly as nickel.) Disadvantages of Platinum: Cost which will make the sparking plug more expensive. A good candidate might justify cost by longer life, better fuel consumption and less pollution. 8 (b) (i) giant structure/lattice/regular arrangements of atoms any for 1 mark of atoms/of ions (provided free electrons mentioned) either for 1 mark delocalised or free electrons for 1 mark 3 (ii) electrons free/can move for 1 mark each 2 [13] M22. (a) (an alloy) that can return to its original shape (after being deformed / bent / twisted) accept (on heating / cooling) it returns to its shape 1 (b) any two from: • brass / it is a mixture accept brass / it is not pure • zinc changes structure / disrupts patterns or layers • copper metal atoms / layers able to slide over each other accept zinc prevents atoms / layers sliding over each other 2 M23. (a) (Chromium =) 20 1 in correct order (Nickel =) 8 accept Chromium = 8 and Nickel = 20 for 1 mark 1 (b) (i) (because iron is made up of only) one type of atom 1 (ii) not strong ignore soft / corrosive / flexible accept it rusts / corrodes or that it could wear away accept could change shape / bend accept layers / atoms could slide (over each other) 1 (iii) has different sized atoms / particles or structure is different/distorted / disrupted accept not in layers or not regular 1 so it is difficult for layers / atoms / particles to slip / slide (over each other) accept layers cannot slip / slide 1 [6] M24. in pure copper the atoms are arranged in layers accept a correct diagram 1 therefore copper is soft because copper atoms can slide over each other 1 in bronze the tin atoms disrupt / distort the structure accept a correct diagram 1 therefore bronze is harder than copper because the metal atoms cannot slide over each other 1 [4] M25. (a) plastic made of polymer chains that can move easily 1 because plastic / polymer has weak intermolecular forces 1 [2] M26. (a) 1-100 nm in size or a few (hundred) atoms in size accept very / really small / tiny or 10–9 accept billionth of a metre or any number that implies very small accept measured in nanometers if answer ‘very small’ ignore incorrect numerical values 1 (b) any two from: • less tennis balls need to be made • tennis balls last longer or don’t have to replace as often • less materials / resources / fuel used up / saves resources accept saving materials • less energy used or making tennis balls uses energy accept saving energy • less pollution caused accept named pollutant accept global warming / greenhouse effect • less waste eg fewer tennis balls going to landfill 2 [3] M27. (a) any one from: • they are made of layers do not accept line / rows / lattice • atoms / ions / particles / layers (of atoms) can slide over each other 1 (b) any one from: • smaller / tiny or very small do not allow small alone • correct size range 1 to 100 nanometres • a few hundred atoms in size if they state smaller and give a size outside range ignore size if it is less than 20,000 1 (c) harder 1 plus one from: • so does not wear as quickly / erode as quickly ignore corrode • less vulnerable to damage owtte harder to wear down = 1 mark • because they have a high surface area to volume ratio or stronger (1) plus one from: (1) • less likely to break / do not break accept withstand pressure • not as vulnerable to damage owtte harder and stronger alone gains 1 mark • do not bend out of shape • because they have a high surface area to volume ratio 1 [4] C2.3 Atomic Structure, Analysis and Quantitative Chemistry - Higher Q1. (a) An atom of aluminium can be represented as shown below. In this atom of aluminium the number of protons is ............................. and the number of neutrons is ............................... (2) (b) Which statement in the table below describes the mass of an electron? Tick ( ) one box. Statement Tick ( ) Electrons have a very small mass compared to protons. Electrons have about the same mass as protons. Electrons are much heavier than protons. Electrons have about the same mass as neutrons. (1) Q2. The diagram represents an atom of beryllium. Use a number from the box to complete each sentence. 4 (a) 7 9 The atomic number (proton number) of this atom is 12 . (1) (b) The mass number of this atom is . (1) Q3. The diagram represents an atom. Choose words from the list to label the diagram. electron ion neutron nucleus (Total 3 marks) Q4. (a) Atoms are made of sub-atomic particles. Complete the six spaces in the table. Name of sub-atomic particle Relative mass Relative charge ................................. 0 ...................... Neutron ..................... ....................... ................................. 1 ....................... (3) (b) Complete the spaces in the sentences. (i) The atomic number of an atom is the number of ..................................... in its nucleus and is equal to the number of ..................................................... if the atom is not charged. (1) (ii) The mass number of an atom is the total number of ................................. and ...................................... in its nucleus. (1) (c) The table gives information about the atoms of three elements. Number of electrons in: Name of element Chemical symbol 1st shell 2nd shell 3rd shell Fluorine F 2 7 0 Neon Ne 2 8 0 Sodium Na 2 8 1 Two of these elements can react together to form a chemical compound. (i) What is the name and the formula of this compound? Name ................................................... Formula .......................................... (2) (ii) What type of bonding holds this compound together? ........................................................................................................................... (1) (iii) Explain, in terms of electron transfer, how the bonding occurs in this compound. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 10 marks) Q5. Atoms are made up of three main particles called protons, neutrons and electrons. Use the periodic table on the data sheet to help you to answer these questions. (a) Sodium is in Group 1 of the periodic table. (i) Why are potassium and sodium in the same Group of the periodic table? ............................................................................................................... ............................................................................................................... (1) (ii) How many protons are in an atom of sodium? ..................................... (1) (iii) The atomic number of sodium is 11. How many neutrons are in an atom of sodium with mass number 23? ...................................... (1) (iv) Each sodium atom has 11 electrons. Complete the electronic structure of sodium. (2) Q6. Calcium oxide (quicklime) is made by heating calcium carbonate (limestone). calcium carbonate → calcium oxide + carbon dioxide 100 g ? 44 g (a) 44 grams of carbon dioxide is produced when 100 grams of calcium carbonate is heated. Calculate the mass of calcium oxide produced when 100 grams of calcium carbonate is heated. .................................................................................................................................... mass ......................... g (1) (b) What mass of carbon dioxide could be made from 100 tonnes of calcium carbonate? mass ....................... tonnes (1) (Total 2 marks) Q7. Calculate the percentage of iron in iron sulphate (FeSO4). (Relative atomic masses: Fe = 56, O = 16, S = 32) ............................................................................................................................................... ............................................................................................................................................... Percentage of iron in iron sulphate = ..........................% (Total 3 marks) Q8. Ammonium chloride, NH4Cl, is made up of nitrogen, hydrogen and chlorine atoms. (i) Complete the table to show the number of atoms of each element present in NH4Cl. Element Number of atoms in NH4Cl nitrogen 1 hydrogen chlorine (1) (ii) Calculate the relative formula mass of ammonium chloride, NH4Cl. (Relative atomic masses: H = 1, N = 14, Cl = 35.5) ..................................................................................................................................... ..................................................................................................................................... Relative formula mass = ................................................. (2) (Total 3 marks) Q9. The diagrams show three isotopes of potassium. (i) In what way does the atomic structure show you that they are all atoms? ..................................................................................................................................... (1) (ii) Explain why these three atoms are called isotopes of potassium. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 4 marks) Q10. The formula for the chemical compound magnesium sulphate is MgSO4. Calculate the relative formula mass (Mr) of this compound. (Show your working.) ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 2 marks) Q11. (a) A chemist was asked to identify a nitrogen compound. The chemist carried out an experiment to find the relative formula mass (Mr) of the compound. The Mr of the compound was 44. Relative atomic masses: N = 14, O = 16 Draw a ring around the formula of the compound. NO NO2 N2O4 N2O (1) (b) Potassium nitrate is another nitrogen compound. It is used in fertilisers. It has the formula KNO3. The Mr of potassium nitrate is 101. Calculate the percentage of nitrogen by mass in potassium nitrate. Relative atomic mass: N = 14. ..................................................................................................................................... ..................................................................................................................................... Percentage of nitrogen = .............................. % (2) (Total 3 marks) Q12. Iron is an essential part of the human diet. Iron(II) sulfate is sometimes added to white bread flour to provide some of the iron in a person’s diet. (a) The formula of iron(II) sulfate is FeSO4 Calculate the relative formula mass (Mr) of FeSO4 Relative atomic masses: O = 16; S = 32; Fe = 56. ..................................................................................................................................... ..................................................................................................................................... The relative formula mass (Mr) = .............................. (2) (b) What is the mass of one mole of iron(II) sulfate? Remember to give the unit. .............................. (1) (c) What mass of iron(II) sulfate would be needed to provide 28 grams of iron? Remember to give the unit. .............................. (1) (Total 4 marks) Q13. The diagram shows the main parts of an instrumental method called gas chromatography linked to mass spectroscopy (GC-MS). This method separates a mixture of compounds and then helps to identify each of the compounds in the mixture. (a) In which part of the apparatus: (i) is the mixture separated? ................................................................... (1) (ii) is the relative molecular mass of each of the compounds in the mixture measured? ............................................................................................................... (1) (b) (i) Athletes sometimes take drugs because the drugs improve their performance. One of these drugs is ephedrine. Ephedrine has the formula: C10H15NO What relative molecular mass (Mr) would be recorded by GC-MS if ephedrine was present in a blood sample taken from an athlete? Show clearly how you work out your answer. Relative atomic masses: H = 1; C = 12; N = 14; O = 16. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... Relative molecular mass = ..................................... (2) (ii) Another drug is amphetamine which has the formula: C9H13N The relative molecular mass (Mr) of amphetamine is 135. Calculate the percentage by mass of nitrogen in amphetamine. Relative atomic mass: N = 14 ............................................................................................................... ............................................................................................................... Percentage of nitrogen = ..................................... % (2) (c) Athletes are regularly tested for drugs at international athletics events. An instrumental method such as GC-MS is better than methods such as titration. Suggest two reasons why. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (d) When a blood sample is taken from an athlete the sample is often split into two portions. Each portion is tested at a different laboratory. Suggest why. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (Total 10 marks) Q14. Perfumes contain a mixture of chemicals. The main ingredients of perfumes are a solvent and a mixture of fragrances. (a) A sample of the solvent used in one perfume contained 0.60 g of carbon, 0.15 g of hydrogen and 0.40 g of oxygen. Relative atomic masses: H = l; C = 12; O = 16. Calculate the empirical (simplest) formula of the solvent. You must show all of your working to gain full marks for this question. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (4) (b) Solvent molecules evaporate easily. Explain why substances made of simple molecules evaporate easily. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Most companies claim that their perfumes have been tested on skin. A study was made of the tests they used. The study found that each company used different tests. The perfumes were tested in the companies’ own laboratories and not by independent scientists. Some companies did not give any information about the tests that they had used. (i) Suggest why companies test their perfumes on skin. ........................................................................................................................... (1) (ii) Did the study show that the tests made by the different companies were valid and reliable? Explain your answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 9 marks) Q15. Cosmetic powders were widely used in ancient Egypt. Cosmetic powders that may have been used in face paints have been analysed. These powders contained compounds that are rare in nature. The compounds must have been made by the ancient Egyptians using chemical reactions. One of these compounds is called phosgenite. Analysis of this compound shows that it contains: 76.0% lead (Pb) 13.0% chlorine (Cl) 2.2% carbon (C) 8.8% oxygen (O) Calculate the empirical formula of this compound. To gain full marks you must show all your working. Relative atomic masses: C = 12 ; O = 16 ; Cl = 35.5 ; Pb = 207 ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (Total 4 marks) Q16. Liquefied petroleum gases such as propane and butane are used as heating fuels for caravans, boats and barbecues. (a) Propane and butane have no smell, so for safety reasons a very small amount of thioethanol – the smelliest substance known – is added, even though it is toxic in large concentrations. Suggest one safety reason why thioethanol is added to propane and butane. ..................................................................................................................................... (1) (b) Suggest how mass spectrometry could be used to distinguish between propane (C3H8) and butane (C4H10). ..................................................................................................................................... ..................................................................................................................................... (1) (c) When 0.4 g of a hydrocarbon gas was completely burned in oxygen, 1.1 g of carbon dioxide and 0.9 g of water were the only products. Relative formula masses: CO2 = 44; H2O = 18. Use this information to calculate the number of moles of carbon dioxide and of water produced in this reaction. Use your answers to calculate the empirical formula of this hydrocarbon. You must show all your working to gain full marks. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... Empirical formula is .............................. (4) (Total 6 marks) Q17. The balanced symbol equation for the reaction is H2 (g) Cl2 (g) → + 2HCl (g) Starting with 2 g of hydrogen, what mass of hydrogen chloride would be produced? (Relative atomic masses: H = 1; Cl = 35.5) ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... Mass of hydrogen chloride = ...................................... g (Total 3 marks) Q18. Iron is the most commonly used metal. Iron is extracted in a blast furnace from iron oxide using carbon monoxide. Fe2O3 (a) + 3CO → Fe + 3CO2 A sample of the ore haematite contains 70% iron oxide. Calculate the amount of iron oxide in 2000 tonnes of haematite. ..................................................................................................................................... ..................................................................................................................................... Amount of iron oxide = ......................................... tonnes (1) (b) Calculate the amount of iron that can be extracted from 2000 tonnes of haematite. (Relative atomic masses: O = 16; Fe = 56) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... Amount of iron = .................................................... tonnes (4) (Total 5 marks) Q19. (a) and (b) (c) (d), (e) and (f) Q20. (a) and (b) M1. (a) 13 1 14 1 numbers must be in the order shown (b) electrons have a very small mass compared to protons 1 (c) electrolysis of molten aluminium oxide 1 [4] M2. (a) 4 1 (b) 9 1 [2] M3. electron nucleus neutron each for 1 mark [3] M4. (a) both correct in each row electron ...– (1) allow negative 1 1 .......... 0 allow neutral or none 1 proton .....+ (1) allow positive 1 (b) (i) protons...electrons both correct in correct order 1 (ii) protons....neutrons both correct in either order 1 (c) (i) sodium fluoride do not credit sodium fluorine 1 NaF must be correct in every detail do not credit NAF and the like 1 (ii) ionic accept ion (bonding) do not credit ironic or iron (bonding) 1 (iii) electron transferred from sodium to fluorine accept electron transferred from metal to non-metal either positive sodium ion and negative fluoride ion or correctly identified by the symbols Na+ and F- accept ‘positive sodium ion and negative fluorine ion’ 1 or attracted because have opposite charge(s) or (atoms/ions) form an (ionic) lattice or (atoms/ions) form a crystal e.g. or both marks may be gained by a suitable dot and cross diagram 1 [10] M5. (a) (i) both have one / 1 electron in the outer energy level / shell allow both react in a similar way 1 (ii) eleven / 11 1 (iii) twelve / 12 1 (iv) (2x) max 1 if candidate changes the number of electrons in the first energy level / shell 8x (in second energy level / shell) 1 1x (in outer energy level / shell) 1 M6. (a) 56g for 1 mark 1 (b) 44 tonnes for 1 mark 1 [2] M7. 36.8 / 37 correct answer, no workings = 3 if incorrect, allow 1 mark for rfm FeSO4 = 152 or if incorrect rfm, allow 1 mark for 56/Y × 100 where Y is incorrect formula mass allow 2 marks for × 100 [3] M8. (i) 4 and 1 both answers must be correct 1 (ii) 53.5 if incorrect relative formula mass allow 1 mark for correct working accept e.c.f. from c(i) for 2 marks 2 [3] M9. (i) same number of protons and electrons accept equal numbers of protons and electrons do not accept they are neutral 1 (ii) same element accept all atoms are potassium 1 same number of protons accept same atomic number accept they all have 19+ 1 different number of neutrons accept different mass numbers do not accept different atomic masses 1 [4] M10. Mg S O4 24 + 32 + 16 (×4) or 64 / evidence of all Ar’s correct [so 24 + 32 + 16 1 mark] gains 1 mark but (Mr) = 120 No ECF gains 2 marks [2] M11. (a) N2O 1 (b) 13.8 to 14 gains full marks without working if answer incorrect 13 gains 1 mark or 14/101 × 100 gains 1 mark 2 [3] M12. (a) 152 correct answer with or without working = 2 marks 56 + 32 + (4 ×16) gains 1 mark ignore any units 2 (b) 152g(rams) ecf from the answer to (a) and g must have unit g / gram / gramme / grams etc accept g / mol or g per mole or g mole–1 or g/mol or g per mol or g mol–1 do not accept g m do not accept G 1 (c) 76(g) ecf from their answer to (a) or (b) divided by 2 ignore units 1 [4] M13. (a) (i) column 1 (ii) mass spectrometer 1 (b) (i) 165 if answer is not correct then evidence of correct working gains one mark. e.g. (10 × 12) + 15 + 14 + 16 2 (ii) 10.37% accept 10 / 10.4 / 10.37............... if answer is not correct then evidence of correct working gains one mark. e.g. minimum evidence would be 14/135 2 (c) any two from: • faster • more accurate • detects smaller amounts 2 (d) to avoid bias accept to check / compare the result 1 to improve reliability 1 [10] M14. (a) C 0.60 H 0.15 O 0.40 1 12 1 = 0.05 = 0.15 16 = 0.025 1 2 6 1 1 C2H6O 1 mark for dividing the correct amount or multiples of correct amount by Ar 1 mark for proportions 1 mark for whole number ratio – accept any multiple 1 mark for correctly written simplest formula correct formula without working gets only 2 marks correct formula gains full marks provided steps 1 and 2 are correct. ecf can be allowed from step 2 to 3 or step 3 to 4 formula can be in any order eg OH6C2 1 (b) intermolecular forces / bonds 1 are weak (covalent) bonds are weak = 0 or forces between molecules or bonds between molecules (1) (attractive) forces are weak = 1 are weak (1) if no marks awarded, allow low boiling point or small Mr for 1 mark 1 (c) (i) to check the safety of the perfume (owtte) accept references to possible harmful / dangerous effects of perfume or possible reactions on skin eg to show it does not damage skin / cause cancer etc. allow to see what it smells like on the skin allow so the company do not have to test on animals 1 (ii) any two from: idea from text linked with an explanation • the company claim to have tested the product: but we cannot be certain they have or how thorough they are or how accurately reported • companies did not disclose how they did their tests: so they could not be checked or so they could not be shown to be reliable / valid or so they could not be repeated or converse eg companies should disclose how they did their tests so that results can be checked etc. • companies may not have repeated their tests: so they may not be reliable • companies do their own tests: so they may be biased or so they may not be truthful about their results or so they may not be reliable or converse eg independent tests should be done so as to ensure there is no bias etc. • the companies are using different tests: so the results cannot be compared or so results will be different or so results will not be fair / valid / reliable or converse eg companies should do the same tests so that the results will be fair etc. • companies would not give false information because of damage to reputation or it might lead to litigation 2 [9] M15. Pb 76 207 Cl 13 35.5 C O 2.2 8.8 12 16 1 mark for dividing one mass by Ar allow upside down ratio to lose this mark only 1 = 0.367 = 0.366 = 0.183 = 0.55 1 mark for one correct proportion – accept to one d.p. or rounded up to 1 d.p. 1 1 mark for all four correct proportions correctly rounded 1 2 2 1 3 or Pb2Cl2CO3 1 mark for correctly written formula or correct whole number ratio correct formula without working gets only 1 mark. e.c.f. can be allowed from incorrect proportions to formula or ratio 1 [4] M16. (a) (smell) warns of a leak / gas escape accept leak / gas escape by implication ignore smell alone 1 (b) eg (mass spectrometry gives) different molecular ions / Mr / formula mass or shows that one has mass 44 and the other 58 ‘mass of butane is more than mass of propane’ is insufficient accept different fragmentation / pattern do not accept Ar / RAM accept references to butane deflects less or converse 1 (c) CO2 1.1 ––– 44 2 H2O 0.9 ––– 18 1 = 0.025 = 0.05 1 1 (mole) CO2 2 (moles) H2O 1 1 or CH4 4 1 or alternative method Mass of C = (1) Mass of H = (1) C:H proportions 0.025 : 0.1 (1) whole number 1 : 4 (1) or CH4 correct formula with no working is only 1 mark M3 can be awarded from the formula if steps one and two are clear correct formula from their incorrect ratio gets 1 mark if fraction is wrong way around e.g. Mr / mass, then lose M1 and M2 but accept ecf for M3 and M4 max 4 [6] M17. 73 (seventy three) if answer is incorrect allow 1 mark for the correct proportion that H2:HCl is 1:2 and 1 mark for 36.5 [3] M18. (a) 1400 1 (b) 980 correct answer gains full credit 160 tonnes Fe2O3 produces 112 tonnes Fe if incorrect allow one mark for relative formula mass iron oxide = 160 allow e.c.f. 1400 tonnes Fe2O3 will produce 1400 / 160 × 112 tonnes Fe use of 2000 tonnes Fe2O3 – deduct one mark only if working out is correct 4 [5] M19. M20. C2.4 Rates of reaction revision - Higher Q1. Hydrogen peroxide (H2O2) contains the same elements as water (H2O). (a) Name the hazard symbol shown by using the correct word from the box. corrosive flammable oxidising toxic (1) (b) Hydrogen peroxide decomposes in the presence of a catalyst. 2H2O2(aq) → 2H2O(l) + O2(g) (i) Complete the word equation for this chemical reaction. hydrogen peroxide → water + ................................ (1) (ii) What does a catalyst do to a chemical reaction? (1) (Total 3 marks Q2. Marble chips (calcium carbonate) react with dilute hydrochloric acid. calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water A student wanted to find out if the size of the marble chips made a difference to how fast the reaction took place. (a) What readings should she take? (2) (b) She repeated the experiment but this time used the same mass (10g) of large marble chips. In both experiments there was some marble left in the flask when the reaction stopped. These are the results of the two experiments. TIME (minutes) 0 2 4 6 8 10 12 Loss in mass (g), using small chips 0.00 0.40 0.72 0.91 1.04 1.04 1.04 Loss in mass (g), using large chips 0.00 0.28 0.52 0.70 0.84 0.94 1.04 (i) Explain the loss in mass in the two experiments. (1) (ii) What difference does the size of the chips make? (1) (c) A chemical reaction occurs when reacting particles collide with sufficient energy. The reaction between marble and hydrochloric acid is faster if the acid is at a higher temperature. Explain why. (3) (Total 7 marks) Q3. The diagram represents the particles in a piece of reactive metal. The piece of reactive metal is added to dilute hydrochloric acid. (a) (i) Which particle will probably react first? Choose from: • • • a particle inside the piece; a particle at the centre of a face; a particle on one of the corners. (1) (ii) Explain the reason for your choice. (1) (b) The reaction can be speeded up by making changes to the hydrochloric acid or the solid. (i) State two ways to speed up the reaction by changing the hydrochloric acid. In each case explain in terms of particles why the reaction is faster. 1. ...................................................................................................................... (2) 2. ...................................................................................................................... (2) (ii) What change can you make to the piece of solid to speed up the reaction? Explain in terms of the particles why the reaction is able to speed up. (2) (Total 8 marks) Q4. A student does an experiment to examine the rate of reaction between magnesium and dilute hydrochloric acid. She adds 25 cm³ of the acid to a weighed amount of the metal. The reaction produces hydrogen gas. Magnesium + hydrochloric acid magnesium + hydrogen chloride She collects the gas and measures the volume collected at one minute intervals. All the metal reacted but there was some acid left unreacted. Her results are shown on the graph. (a) The diagram shows part of the apparatus she used for the experiment. Complete the diagram to show how the student could collect the hydrogen produced and measure the volume after each minute. (2) (b) (i) When is the rate of reaction at its fastest? (1) (ii) State one way in which she could increase the rate of reaction. .......................................................................................................................... (1) (c) (i) What is the total volume of hydrogen collected in the experiment? ................................................................................................................... cm³ (1) (ii) State one way in which she could increase the final volume of hydrogen collected. .......................................................................................................................... (1) (Total 6 marks) Q5. Sodium thiosulfate solution reacts with hydrochloric acid. As the reaction takes place the solution slowly turns cloudy.The diagram shows a method of measuring the rate of this reaction. A student used this method to investigate how changing the concentration of the sodium thiosulfate solution affects the rate of this reaction. The student used different concentrations of sodium thiosulfate solution. All the other variables were kept the same. The results are shown on the graph below. (a) (i) Draw a line of best fit on the graph. (1) (ii) Suggest two reasons why all of the points do not lie on the line of best fit. 1 ........................................................................................................................ ........................................................................................................................... 2 ........................................................................................................................ (2) (b) (i) In a conclusion to the investigation the student stated that: ‘The rate of this reaction is directly proportional to the concentration of the sodium thiosulfate solution.’ How does the graph support this conclusion? (1) (ii) Explain, in terms of particles, why the rate of reaction increases when the concentration of sodium thiosulfate is increased. (2) (Total 6 marks) M1. (a) oxidising 1 (b) (i) oxygen ignore any numbers 1 (ii) (catalyst) speeds up a (chemical reaction) accept changes the rate (of reaction) 1 [3 M2. (a) ideas that • ref to read the balance / read the mass / weight • ref to read the stop clock / read the time • ‘readings’ taken at the beginning and end / at regular intervals for 1 mark each 2 (b) (i) • loss of carbon dioxide (from the flask) } • (ii) smaller chips give faster reaction / reaction } mark as a whole finishes quicker /dissolved faster [or reverse] } • smaller chips have a larger surface area } any 2 for 1 mark each [Allow converse answers] 2 (c) ideas that • heating increases the speed / energy / vibration of the (acid) particles / marble particles • (acid) particles collide (with marble chips / (particles)) more frequently / more likely to collide • reacting particles collide with greater energy / collide faster • so particles more likely to react [do not accept ‘react faster’] [Accept ‘atoms’, ‘molecules’ or ‘ions’ instead of ‘particles’ in this question] any three for 1 mark each 3 [7 M3. (a) (i) corners accept an arrow to any corner 1 (ii) more (surface) exposed accept can be attacked from more directions or more space around it 1 (b) (i) 1 any two pairs from more concentrated answers may be in either order do not accept more acid do not accept more powerful or stronger (but stronger is neutral) a reference to sulphuric acid is neutral 1 more particles to hit the solid accept more collisions per second do not accept more collisions 1 2 hotter solution or increasing temperature (faster) particles hit more often or harder accept particles have more energy or are more powerful or more successful collisions 1 3 stirring more surface area exposed or particles available accept more collisions per second do not accept more collisions 1 (ii) cut it up or increase the surface area accept grind it up or powder it or flatten it do not accept make it smaller or use a smaller piece 1 more particles are exposed or available or can react accept heat it and there are more successful collisions for both marks 1 [8] M4. (a) (must be possible for the gas to enter and displace the water) or other suitable apparatus • apparatus to collect the gas correctly assembled for 1 mark • calibrated collection vessel (award even if diagram is wrong) for 1 mark 2 (b) (i) at the start / in the first 1/2 minutes (or any time within this range) for 1 mark 1 (ii) increase the temperature / use smaller pieces of metal / use more metal / increase the surface area of the metal / add a catalyst / shake the flask / increase the concentration / strength of the acid for 1 mark 1 (c) (i) 48 for 1 mark 1 (ii) increase the amount of magnesium used for 1 mark (do not allow increase the amount of acid used) 1 [6] M5. (a) (i) a continuous straight line missing anomalous point allow a line which does not start at zero / origin 1 (ii) any two sensible errors eg • timing errors and / or example(*) • measurement errors and / or example(*) • apparatus errors and / or example(*) • human / experimental / random error and / or example or ‘did not do it right’(*) (*)could be two from same category eg two timing errors – watch not started at the same time plus difficulty in deciding when the cross has disappeared. • temperature fluctuation • anomalous point accept outlier / wrong result • results not recorded correctly • plotting error • rate calculated incorrectly ignore ‘not repeated’ ignore systematic / zero error / weighing error or error unqualified 2 (b) (i) straight line or as concentration increases the rate goes up or converse accept numerical example accept positive correlation accept same gradient ignore ‘most points near / on line of best fit’ 1 (ii) more collisions accept greater chance of collisions accept collide more successfully accept alternative versions of collide eg ‘bump / hit’ ignore references to energy / speed of particles / surface area 1 more particles (in each volume of solution)(i.e. an attempt at defining concentration) accept ‘particles are closer together’ allow ions / atoms / molecules for particles ignore reactants accept greater frequency of collisions or greater number of collisions per second for 2 marks 1 C2.5 Exothermic and endothermic reactions Revision Higher Q1. Distress flares are used to attract attention in an emergency. Flares often contain magnesium. Magnesium burns to form magnesium oxide. (a) The distress flare burns with a bright flame because the reaction is very exothermic. Complete the following sentence using the correct words from the box. gives out heat stores heat takes in heat An exothermic reaction is one which .......................................................................... (1) (b) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach. Draw a ring around the name of the salt formed when magnesium oxide reacts with hydrochloric acid. magnesium chloride magnesium hydroxide magnesium sulfate (1) Q2. An indigestion tablet contains sodium hydrogencarbonate and citric acid. When the tablet is added to cold water a chemical reaction takes place and there is a lot of fizzing. (a) The formula of the gas that causes the fizzing is CO2 Name this gas ......................................................................... . (1) (b) This chemical reaction is endothermic. (i) Tick ( ) the statement which describes what happens to the temperature of the solution. Statement Tick ( ) The temperature of the solution will increase. The temperature of the solution will decrease. The temperature of the solution will stay the same. (1) (ii) Tick ( ) the statement which describes what happens to the energy during the reaction. Statement Tick ( ) Energy is given out to the surroundings. Energy is taken in from the surroundings. No energy is given out to or taken from the surroundings. (1) Q3. Instant cold packs are used to treat sports injuries. One type of cold pack has a plastic bag containing water. Inside this bag is a smaller bag containing ammonium nitrate. The outer bag is squeezed so that the inner bag bursts. The pack is shaken and quickly gets very cold as the ammonium nitrate dissolves in the water. (a) One of the statements in the table is correct. Put a tick ( ) next to the correct statement. Statement ( ) The bag gets cold because heat energy is given out to the surroundings. The bag gets cold because heat energy is taken in from the surroundings. The bag gets cold because plastic is a good insulator. (1) (b) Draw a ring around the word that best describes the change when ammonium nitrate dissolves in water. electrolysis endothermic exothermic (1) (c) Suggest and explain why the pack is shaken after the inner bag has burst. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q4. The diagram shows some magnesium ribbon burning. (a) Choose words from the list to complete the sentences below. electrical an endothermic heat an exothermic light a neutralisation kinetic a reduction When magnesium burns, it transfers ......................................................................... and ............................................................................ energy to the surroundings. We say that it is .................................................................................. reaction. (3) (b) Complete the word equation for the reaction. magnesium + __________________________ magnesium oxide (1) (Total 4 marks) Q5. The diagram shows the apparatus for an experiment. Hydrated copper sulphate crystals were heated. They became anhydrous copper sulphate. (a) Name a suitable piece of equipment to heat tube A. ..................................................................................................................................... (1) (b) Use words from the box to complete the two spaces in the table. You may use each word once or not at all. black blue orange red purple white Name Colour Hydrated copper sulphate crystals ................................................... Anhydrous copper sulphate .................................................... (2) (c) What is the purpose of the ice and water in the beaker? ..................................................................................................................................... ..................................................................................................................................... (1) (d) Drops of a clear, colourless liquid formed on the inside of tube B. (i) Name the liquid. ........................................................................................................................... (1) (ii) Explain how the liquid came to be inside tube B. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (e) Anhydrous copper sulphate can be turned into hydrated copper sulphate. What would you need to add? Apart from the change in colour, what could you observe? ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (f) Copper sulphate can be made from black copper oxide by reacting it with an acid. Name the acid. ..................................................................................................................................... (1) (Total 10 marks) Q6. A student did two experiments using ammonium chloride. (a) In the first experiment the student heated a small amount of ammonium chloride in a test tube. Two reactions take place in the test tube. Reaction 1 Reaction 2 (i) ammonium chloride → ammonia + hydrogen chloride (colourless gases) ammonia + hydrogen chloride → ammonium chloride Complete the sentences by crossing out the incorrect word in each box. Reaction 1 takes place at a high low temperature. Reaction 2 takes place at a high low temperature. (1) (ii) Draw a ring around the word which best describes reactions 1 and 2. combustion displacement oxidation reduction reversible (1) (iii) Suggest a reason for the mineral wool at the top of the test tube. ........................................................................................................................... ........................................................................................................................... (1) (b) In the second experiment the student mixed a small amount of ammonium chloride with some water in a beaker. The temperature of the water was measured before and after adding the ammonium chloride. Temperature before adding the ammonium chloride 20°C Temperature after adding the ammonium chloride 16°C Draw a ring around the word which best describes the process which takes place. combustion displacement endothermic exothermic freezing (1) (Total 4 marks) M1. (a) gives out (heat) 1 (b) magnesium chloride 1 [2] M2. (a) carbon dioxide must be name do not accept carbon oxide 1 (b) (i) the temperature of the solution will decrease (list principle) 1 (ii) energy is taken in from the surroundings (list principle) 1 [3] M3. (a) the bag gets cold because heat energy is taken in from the surroundings 1 (b) endothermic 1 (c) any two from: • mix / spread (the ammonium nitrate and water) • dissolve faster(*) • get cold faster or so the whole bag gets cold(*) (*)allow increase rate or quicker reaction • particles collide more or more collisions 2 [4] M4. (a) heat light an exothermic in any order for 1 mark each 3 (b) oxygen / O2 for 1 mark 1 [4] M5. (a) Bunsen (burner) accept spirit burner do not credit candle 1 (b) blue 1 white credit (1) if both colours correct but answers are reversed 1 to cool the tube (B) accept answers which anticipate part (d) e.g. ‘to condense the water vapour’ or gases or vapours 1 (d) (i) water do not credit ‘condensation’ 1 (ii) (Water) vapour from the crystals (from tube A) accept steam or steam from tube A 1 condenses or cools accept turns to (liquid) water 1 (e) add water gets hot or hotter or warm or warmer turns into solution dissolves or the temperature rises or there is an exothermic reaction accept steams or hisses ignore any reference to colour(s) 2 (f) sulphuric acid accept H2S04 only if correct in every detail 1 [10] M6. (a) (i) high and low both needed for mark 1 (ii) reversible 1 (iii) to prevent ammonium chloride / solid / particles escaping idea of a filter do not accept ‘to prevent gases escaping’ 1 (b) endothermic 1 [4] C2.5 Exothermic and endothermic reactions Revision Higher Q1. Distress flares are used to attract attention in an emergency. Flares often contain magnesium. Magnesium burns to form magnesium oxide. (a) The distress flare burns with a bright flame because the reaction is very exothermic. Complete the following sentence using the correct words from the box. gives out heat stores heat takes in heat An exothermic reaction is one which .......................................................................... (1) (b) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach. Draw a ring around the name of the salt formed when magnesium oxide reacts with hydrochloric acid. magnesium chloride magnesium hydroxide magnesium sulfate (1) Q2. An indigestion tablet contains sodium hydrogencarbonate and citric acid. When the tablet is added to cold water a chemical reaction takes place and there is a lot of fizzing. (a) The formula of the gas that causes the fizzing is CO2 Name this gas ......................................................................... . (1) (b) This chemical reaction is endothermic. (i) Tick ( ) the statement which describes what happens to the temperature of the solution. Statement Tick ( ) The temperature of the solution will increase. The temperature of the solution will decrease. The temperature of the solution will stay the same. (1) (ii) Tick ( ) the statement which describes what happens to the energy during the reaction. Statement Tick ( ) Energy is given out to the surroundings. Energy is taken in from the surroundings. No energy is given out to or taken from the surroundings. (1) Q3. Instant cold packs are used to treat sports injuries. One type of cold pack has a plastic bag containing water. Inside this bag is a smaller bag containing ammonium nitrate. The outer bag is squeezed so that the inner bag bursts. The pack is shaken and quickly gets very cold as the ammonium nitrate dissolves in the water. (a) One of the statements in the table is correct. Put a tick ( ) next to the correct statement. Statement The bag gets cold because heat energy is given out to the surroundings. The bag gets cold because heat energy is taken in from the surroundings. The bag gets cold because plastic is a good insulator. ( ) (1) (b) Draw a ring around the word that best describes the change when ammonium nitrate dissolves in water. electrolysis endothermic exothermic (1) (c) Suggest and explain why the pack is shaken after the inner bag has burst. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q4. The diagram shows some magnesium ribbon burning. (a) Choose words from the list to complete the sentences below. electrical an endothermic heat an exothermic light a neutralisation kinetic a reduction When magnesium burns, it transfers ......................................................................... and ............................................................................ energy to the surroundings. We say that it is .................................................................................. reaction. (3) (b) Complete the word equation for the reaction. magnesium + __________________________ magnesium oxide (1) (Total 4 marks) Q5. The diagram shows the apparatus for an experiment. Hydrated copper sulphate crystals were heated. They became anhydrous copper sulphate. (a) Name a suitable piece of equipment to heat tube A. ..................................................................................................................................... (1) (b) Use words from the box to complete the two spaces in the table. You may use each word once or not at all. black blue orange red purple white Name Colour Hydrated copper sulphate crystals ................................................... Anhydrous copper sulphate .................................................... (2) (c) What is the purpose of the ice and water in the beaker? ..................................................................................................................................... ..................................................................................................................................... (1) (d) Drops of a clear, colourless liquid formed on the inside of tube B. (i) Name the liquid. ........................................................................................................................... (1) (ii) Explain how the liquid came to be inside tube B. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (e) Anhydrous copper sulphate can be turned into hydrated copper sulphate. What would you need to add? Apart from the change in colour, what could you observe? ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (f) Copper sulphate can be made from black copper oxide by reacting it with an acid. Name the acid. ..................................................................................................................................... (1) (Total 10 marks) Q6. A student did two experiments using ammonium chloride. (a) In the first experiment the student heated a small amount of ammonium chloride in a test tube. Two reactions take place in the test tube. Reaction 1 Reaction 2 (i) ammonium chloride → ammonia + hydrogen chloride (colourless gases) ammonia + hydrogen chloride → ammonium chloride Complete the sentences by crossing out the incorrect word in each box. Reaction 1 takes place at a high low temperature. Reaction 2 takes place at a high low temperature. (1) (ii) Draw a ring around the word which best describes reactions 1 and 2. combustion displacement oxidation reduction reversible (1) (iii) Suggest a reason for the mineral wool at the top of the test tube. ........................................................................................................................... ........................................................................................................................... (1) (b) In the second experiment the student mixed a small amount of ammonium chloride with some water in a beaker. The temperature of the water was measured before and after adding the ammonium chloride. Temperature before adding the ammonium chloride 20°C Temperature after adding the ammonium chloride 16°C Draw a ring around the word which best describes the process which takes place. combustion displacement endothermic exothermic freezing (1) (Total 4 marks) M1. (a) gives out (heat) 1 (b) magnesium chloride 1 [2] M2. (a) carbon dioxide must be name do not accept carbon oxide 1 (b) (i) the temperature of the solution will decrease (list principle) 1 (ii) energy is taken in from the surroundings (list principle) 1 [3] M3. (a) the bag gets cold because heat energy is taken in from the surroundings 1 (b) endothermic 1 (c) any two from: • mix / spread (the ammonium nitrate and water) • dissolve faster(*) • get cold faster or so the whole bag gets cold(*) (*)allow increase rate or quicker reaction • particles collide more or more collisions 2 [4] M4. (a) heat light an exothermic in any order for 1 mark each 3 (b) oxygen / O2 for 1 mark 1 [4] M5. (a) Bunsen (burner) accept spirit burner do not credit candle 1 (b) blue 1 white credit (1) if both colours correct but answers are reversed 1 to cool the tube (B) accept answers which anticipate part (d) e.g. ‘to condense the water vapour’ or gases or vapours 1 (d) (i) water do not credit ‘condensation’ 1 (ii) (Water) vapour from the crystals (from tube A) accept steam or steam from tube A 1 condenses or cools accept turns to (liquid) water 1 (e) add water gets hot or hotter or warm or warmer turns into solution dissolves or the temperature rises or there is an exothermic reaction accept steams or hisses ignore any reference to colour(s) 2 (f) sulphuric acid accept H2S04 only if correct in every detail 1 [10] M6. (a) (i) high and low both needed for mark 1 (ii) reversible 1 (iii) to prevent ammonium chloride / solid / particles escaping idea of a filter do not accept ‘to prevent gases escaping’ 1 (b) endothermic 1 [4] C2.6 Making salts Revision Higher Q1. Use the Formulae of Some Common Ions table on the Data Sheet to help you to answer this question. Acids react with alkalis to form salts and water. Complete the table below by writing in the name and formula of the salt formed in each reaction. The first one has been done for you. Acid Alkali Salt Formula of salt Hydrochloric acid Sodium hydroxide Sodium chloride NaCl Nitric acid Sodium hydroxide Sulphuric acid Potassium hydroxide (Total 4 marks) Q2. In this question you will get marks on using good English, organising information clearly and using specialist terms correctly. Copper sulfate crystals can be made from copper oxide powder and dilute sulfuric acid. Describe a method to make copper sulfate crystals from copper oxide and dilute sulfuric acid. For the method you should include: • • the names of the pieces of apparatus used a risk assessment. (Total 6 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... Q3. (a) Neutralisation reactions can be used to make salts. Write an ionic equation for a neutralisation reaction, including state symbols. ..................................................................................................................................... (2) (b) Ammonium nitrate is a salt used as a fertiliser. (i) Ammonium nitrate is made by mixing two solutions. Name these solutions. ......................................................... and ......................................................... (1) (ii) Hazard information about ammonium nitrate states: • it is not itself a fire hazard (does not burn); • it must not be allowed to come into contact with combustible materials such as fuels because it can cause these to catch fire. Suggest why ammonium nitrate helps other substances to burn. (1) (Total 4 marks) Q4. When a solution of lead nitrate is added to a solution of sodium chloride, a white precipitate of lead chloride is produced. (a) (i) Why is a precipitate formed? (1) (ii) Complete and balance the equation for this precipitation reaction. Pb+2(aq) + Cl–(aq) → (3) (b) Complete the table below by writing in the name and formula of the precipitate formed for each reaction. If there is no precipitate, write “no precipitate”. (5) Here is a symbol equation, with state symbols, for a chemical reaction between solutions of lead nitrate and potassium chloride. Pb (NO3)2 (aq) + 2 KCl (aq) 2KNO3 (aq) + PbCl2 (s) The equation tells you the formulae of the two products of the reaction. (a) What are the names of the two products? (2) (b) What else does the equation tell you about these products? (2) Q6. Photographic film often contains silver bromide. Silver bromide is changed by light to form silver which appears as a black solid. This darkens the photographic film.A photographic film can be made by coating thin transparent plastic with a gel containing silver bromide. The main steps in making this photographic film are as follows: Step 1 Gelatine is dissolved in warm water to make a solution. Step 2 is Compound A, a soluble compound which contains bromide ions, dissolved into this solution. Step 3 The lights are turned out in the darkroom. Step 4 is Compound B, a soluble compound which contains silver ions, dissolved in water. Step 5 The solution of compound B is added to the solution containing compound A and gelatine. Solid silver bromide is formed. Step 6 The warm mixture is poured onto thin, transparent plastic film. Step 7 The mixture sets to form a gel containing solid silver bromide. (a) The table below gives information about the solubility of some compounds. SOLUBLE INSOLUBLE All sodium and potassium salts All nitrates Most chlorides, bromides and iodides Silver and lead chlorides, bromides and iodides Most sulfates Lead sulfate and barium sulfate Sodium, potassium and ammonium carbonates Most other carbonates Use the table to help you to name suitable compounds for A and B. Compound A .............................................................................................................. Compound B .............................................................................................................. (2) (b) Suggest why the lights are turned out at step 3 in this method of making a photographic film. (1) (c) What type of chemical reaction takes place when the compounds are mixed in step 5? (1) (d) The photographic film is placed in a camera and a picture is taken. Where light hits the photographic film the silver ions (Ag+) are changed into silver metal (Ag). Explain why this reaction is a reduction. (2) (Total 6 marks) Q7. (i) Ammonium nitrate and ammonium sulphate are used as fertilisers. Which acid reacts with ammonia to form ammonium nitrate? .................................................................................................................................... (1) (ii) Which acid reacts with ammonia to form ammonium sulphate? .................................................................................................................................... (1) (iii) The reactions in (i) and (ii) are both exothermic. How can you tell that a reaction is exothermic? .................................................................................................................................... (1) (iv) The reactions in (i) and (ii) are both examples of acid + base reactions. What is the name of the chemical change which takes place in every acid + base reaction? .................................................................................................................................... (1) (Total 4 marks) Q8. The following passage is about the preparation of lead iodide, an insoluble salt. An excess of potassium iodide in solution was shaken with some lead nitrate solution in a test tube. The lead iodide precipitate was separated from the mixture and then washed several times with water. The lead iodide was dried and then placed in a bottle. (a) Suggest a reason why excess potassium iodide was used. ..................................................................................................................................... (1) (b) What word used in the passage shows that lead iodide is insoluble? .................................................................................................................................... (1) (c) Suggest how lead iodide can be separated from the mixture. .................................................................................................................................... (1) (d) Why was the lead iodide washed with water? .................................................................................................................................... (1) (e) Suggest a method which could be used to dry this lead iodide. .................................................................................................................................... (1) (f) Lead compounds are toxic. Suggest a suitable safety precaution that should be taken when using toxic substances in laboratories. .................................................................................................................................... (1) (Total 6 marks) Q9. The diagrams show what happens when an acid is added to an alkali. (a) What is present in the flask at stage 2, besides universal indicator and water? ..................................................................................................................................... (1) (b) Write an ionic equation to show how water is formed in this reaction and state the sources of the ions. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (Total 4 marks) M1. sodium nitrate 1 NaNO3 do not credit lower case N or O, upper case A 1 potassium sulphate 1 K2SO4 accept potassium hydrogen sulphate or do not credit lower case K, S or O ignore charges on ions KHSO4 1 [4] M2. Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. No relevant content. 0 marks There is a brief description of the method or a risk assessment. Level 1 (1–2 marks) There is some description of the method that may include a risk assessment. Level 2 (3–4 marks) There is a clear, balanced and detailed description of the method and a risk assessment. Level 3 (5–6 marks) examples of the chemistry points made in the response The underlined words are needed to gain each bullet point. • sulfuric acid is heated in a beaker and copper oxide is added with stirring • until the copper oxide is in excess • the mixture is filtered or the mixture is poured through a funnel and filter paper • to remove the excess copper oxide • some of the solution is evaporated or heated in an evaporating basin/dish • the solution is allowed to crystallise / cool down examples of the risk assessment points made in the response • wear safety goggles – to protect eyes because sulfuric acid is corrosive / an irritant • care when heating – to protect against burns • wash hands after the preparation – copper sulfate is harmful • care when handling glass apparatus – to protect against cuts [6] M3. (a) H+(aq) + OH– (aq) → H2O(l) or H3O+(aq) + OH–(aq) → H2O(l) mark for correct equation mark for state symbols any other symbols = 0 marks accept correct spectator ions e.g. Na+(aq) + OH– (aq) + H+(aq) + Cl– (aq) → Na+(aq) + Cl– (aq) + H2O(l) 2 (b) (i) HNO3 nitric acid and ammonia (solution) NH3 / NH4OH mark for both accept ammonium hydroxide / NH4OH instead of ammonia do not accept ammonia hydroxide do not accept hydrogen nitrate solution accept correct formulae 1 (ii) provides oxygen or oxidising (agent) or oxidant do not accept it contains oxygen alone or rich in oxygen 1 [4] M4. (a) (i) lead chloride/product of lead + chloride ions is insoluble (in water) for 1 mark 1 (ii) Pb2+ + 2C1¯ → PbC12 *(s) (allow (Pb)2+ 2 (C1–) ) formula solid state symbol balancing for 1 mark each 3 (b) copper hydroxide Cu(OH)2 each for 1 mark lead sulphate PbSO4 each for 1 mark no precipitate for 1 mark Allow 1 mark for correct formula Na2SO4 in (i) Allow 1 mark for correct formula Mg (NO3)2 in (ii) 0 marks for any formula in (iii) 5 [9] M5. (a) lead chloride potassium nitrate } } in any order for 1 mark each 2 (b) lead chloride is solid / a precipitate potassium nitrate is aqueous / in solution / dissolves in water NOT liquid for 1 mark each 2 (Accept ratio of molecular KNO3 : PbC12 is 2:1 for 2 marks) (do not accept relative number of atoms in each compound) One is a solid, one is a solution – worth 1 mark [4] M6. (a) Compound A any one from: accept correct formulae • sodium bromide • potassium bromide • ammonium bromide • hydrogen bromide • any metal bromide except silver and lead. 1 Compound B silver nitrate accept silver sulphate 1 (b) the silver compound will decompose / silver ions be reduced to silver (owtte) accept film would darken owtte accept any idea of light changing silver bromide / silver ions / silver nitrate / silver sulphate allow ‘forms a black solid’ / it would turn black 1 (c) precipitation accept descriptions of precipitation reactions accept double decomposition accept precipitate do not allow displacement 1 (d) electrons 1 are gained the second mark must be linked to electrons accept it / silver / silver ions gains electrons for both marks ignore references to oxygen 1 [6] M7. (i) nitric (acid) accept HN03 1 (ii) sulphuric (acid) accept H2SO4 1 (iii) heat given out or temperature rise or energy given out or steam do not credit just ‘use a thermometer’ do not credit just 'change in temperature' 1 (iv) neutralisation accept neutralise accept neutral accept formation of salt or water do not credit exothermic 1 [4] M8. (a) all lead nitrate reacted or no lead nitrate left or enough KI to react with lead nitrate or to remove all the lead ions or to get maximum amount of I2 ignore comments about speed do not accept to remove all the lead 1 (b) precipitate allow phonetic spelling do not accept ppt 1 1 (c) filter / filtration / centrifuge / decant do not accept sieve (d) any one from: • removes (soluble) impurities • removes (unreacted) KI • removes KNO3 • removes (excess) solution • removes nitrates purifying is insufficient do not accept removes potassium do not accept removes iodide 1 (e) answer based on filter paper, desiccator, suitable solvent (gentle) heat, drying cabinet, oven etc. Accept any method of heating i.e. bunsen / hairdryer etc. Accept leave to evaporate / stand or leave in a warm room e.g. place between dry filter paper, allow to dry e.g. use propanone, allow to dry e.g. leave on sunny window sill e.g. leave in a draught the answer leave / evaporate / draught alone is insufficient 1 (f) wear gloves / mask or fume-cupboard or wash hands afterwards ignore goggles / labcoat or extractor fan / do not touch etc. 1 [6] M9. (a) sodium ions and chloride ions (not chlorine) allow sodium chloride/salt/common salt for 1 mark 1 (b) H+ + OH– →H2O H+ from (hydrochloric) acid OH- from alkali/sodium hydroxide lose 1 mark if no charge shown disregard other ions each for 1 mark 3 [4] C2.7 Electrolysis Revision - Higher Q1. A student investigated the electrolysis of lead bromide. Lead bromide was placed in the tube and the circuit was switched on. The light bulb did not light up. The tube was heated and soon the bulb lit up. The observations are shown in the table. Positive electrode Negative electrode red-brown gas silver liquid (a) What is meant by electrolysis? .................................................................................................................................... (2) (b) Why did the lead bromide conduct electricity when the tube was heated? .................................................................................................................................... (1) (c) Name the substances formed at the: positive electrode; ..................................................................................................... negative electrode. .................................................................................................... (2) (d) Suggest one safety precaution that should be taken during this investigation. .................................................................................................................................... (1) (Total 6 marks) Q2. (a) (i) Two experiments were set up as shown. Give two observations which would be seen only in Experiment D. 1 ....................................................................................................................... 2 ....................................................................................................................... (2) (ii) Explain why in Experiment C no changes would be seen. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (b) Another electrolysis experiment used an aqueous solution of copper chloride. (i) What does electrolysis mean? ........................................................................................................................... ........................................................................................................................... (2) (ii) Name the gas A and the deposit B. Gas A ................................................................................................................ Deposit B .......................................................................................................... (2) (c) Give one industrial use of electrolysis. ..................................................................................................................................... (1) (Total 9 marks) Q3. An investigation into the electrolyte copper sulphate solution was carried out as shown. (a) What does electrolyte mean? ..................................................................................................................................... (2) (b) These were the observations. Negative electrode solid formed Positive electrode gas given off (i) Name the solid formed. .......................................................................................................................... (1) (ii) Name the gas given off. .......................................................................................................................... (1) (c) How could a sample of gas be collected at the positive electrode? .................................................................................................................................... .................................................................................................................................... (2) (d) Suggest why the blue colour of copper sulphate becomes paler during the investigation. .................................................................................................................................... .................................................................................................................................... (2) (Total 8 marks) Q4. The electrolysis of sodium chloride solution produces useful substances. (a) Explain the meaning of electrolysis. ..................................................................................................................................... ..................................................................................................................................... (2) (b) The diagram shows an apparatus used for the electrolysis of sodium chloride solution. The electrolysis produces two gases, chlorine and Gas A. Name Gas A ............................................................................................................... (1) (c) The electrodes used in this process can be made of graphite. Explain why graphite conducts electricity. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 5 marks) Q5. Read the information in the box and then answer the question. Aluminium is made by the electrolysis of aluminium oxide. Aluminium oxide is an ionic compound containing aluminium ions (Al3+) and oxide ions (O2–). The diagram below shows the apparatus used to electrolyse aluminium oxide. (a) In this question you will get marks on using good English, organising information clearly and using specialist terms correctly. Use information in the box and your knowledge and understanding of this process to answer this question. Explain, as fully as you can, how aluminium and carbon dioxide are formed in this process. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (6) (b) Aluminium is a metal. Explain why aluminium conducts electricity. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (Total 8 marks) Q6. Electrolysis can be used to remove unwanted hair from the skin. The hair is first coated with a layer of gel containing ions in solution. The positive electrode is connected by a patch to the skin. The negative electrode is connected to the hair. Electricity flows through the gel and causes electrolysis of the body fluid around the hair follicle. (a) Metal wires conduct electricity to the electrodes. Explain how metals conduct electricity. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Explain why the gel containing ions in solution can conduct electricity. ..................................................................................................................................... ..................................................................................................................................... (1) (c) The body fluid is a solution that contains sodium chloride. The electricity causes the electrolysis of a small amount of this solution. This solution contains hydrogen ions that move to the negative electrode. (i) The half equation represents the reaction at the negative electrode. 2H+ + 2e– → H2 Explain why this reaction is a reduction. ........................................................................................................................... ........................................................................................................................... (1) (ii) As a result of the electrolysis of sodium chloride solution, an alkali forms which kills the hair follicle. What is the name of this alkali? ....................................................................... (1) (iii) Complete the half equation for the reaction at the positive electrode. Cl – → Cl2 (1) (Total 6 marks) Q7. The diagram below shows the electrolysis of sodium chloride solution, in the laboratory. (a) Which gas forms at the negative electrode? .............................................................. (1) (b) Explain why chlorine gas forms at the positive electrode. ..................................................................................................................................... ..................................................................................................................................... (2) (c) State one use of chlorine gas. ..................................................................................................................................... (1) (Total 4 marks) Q8. Sodium chloride solution is a useful raw material for the manufacture of other substances. (i) What is the name of the process shown? ..................................................................................................................................... (1) (ii) Chloride ions lose electrons at the positive electrode. What is the name of this type of reaction? ..................................................................................................................................... (1) (iii) The solution formed at X is alkaline. What causes this solution to be alkaline? ..................................................................................................................................... ..................................................................................................................................... (2) (iv) Give a balanced ionic equation for the formation of hydrogen gas at the negative electrode. ..................................................................................................................................... (3) (Total 7 marks) M1. (a) breakdown / decomposition / splits into elements / not ions separates into elements / produce a chemical reaction 1 using electricity 1 (b) lead bromide melted / free ions not electrolyte 1 (c) (+) bromine element must be appropriate to electrode 1 (–) lead element must be appropriate to electrode 1 (d) fume cupboard / protective clothing allow safety glasses not safety mat 1 [6] M2. (a) (i) bulb lights up 1 bubbles / fizz / gas or chlorine given off 1 (ii) in solid, ions 1 are not free to move / (charged) particles cannot move or converse atoms / electrons cannot move worth 0 marks 1 (b) (i) breakdown / decomposition / splitting up not separation 1 by using electricity 1 (ii) gas A = chlorine / oxygen 1 deposit B = copper 1 (c) any one from: • manufacturer of chlorine / sodium hydroxide / hydrogen / sodium • electroplating of steel / reference to plating not galvanising • extraction of aluminium / metal reactivity series specified • purification of copper not making copper 1 [9] M3. (a) substance brokendown / separates / splits into elements by electric current / electricity ions free to move e.g. when molten / in solution allow 1 mark for “a substance that conducts electricity” max 2 (b) (i) copper / Cu 1 (ii) oxygen /O2 allow CO2 1 (c) tube over electrode full of CuSO4(aq) / water allow sulphuric acid / sensible electrolyte not any other liquid / using a syringe 2 (d) Cu2+ ions removed / less Cu2+ not copper sulphate removed allow 1 mark for “copper removed / less copper” 2 [8] M4. (a) electric current / electricity 1 plus one from: • is passed through ionic compound / substance / electrolyte • passed through molten/aqueous compound / substance must be linked to electricity allow liquid compound / substance do not allow solution / liquid alone • causing decomposition accept split up / breakdown / breaking up owtte ignore separated accept elements are formed ignore new substances form 1 (b) hydrogen accept H2 do not accept H / H2 1 (c) one electron from each atom accept each carbon is bonded to three other carbon atoms leaving one (unbonded) electron owtte 1 is delocalised / free (to move) must be linked to electrons answers of delocalised / free electrons only, gains 1 mark accept each carbon is bonded to three other carbon atoms leaving delocalised / free electrons = 2 marks maximum 1 mark if graphite described as a metal / giant ionic lattice 1 [5] M5. (a) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. No relevant content. 0 marks There is a brief description of the electrolysis of aluminium oxide. Level 1 (1–2 marks) There is some description of the electrolysis of aluminium oxide. Level 2 (3–4 marks) There is a clear, balanced and detailed description of the electrolysis of aluminium oxide. Level 3 (5–6 marks) examples of the chemistry points made in the response • aluminium oxide is melted / made liquid • aluminium ions are attracted to the negative electrode • at the negative electrode aluminium is formed or aluminium ions gain electrons • oxide ions are attracted to the positive electrode • oxygen is formed at the positive electrode or oxide ions lose electrons • the oxygen reacts with carbon to make carbon dioxide or carbon dioxide formed at positive electrode. (b) there are delocalised electrons / free electrons / electrons which move within the aluminium / metallic structure 1 therefore these electrons are able to carry the current / charge 1 if the candidates use the terms covalent / ionic / molecules / intermolecular incorrectly in the answer this will limit the mark to a maximum of 1. [8] M6. (a) any two from: • outer shell electrons / electrons in highest energy level (in metals) • electrons are delocalised / sea of electrons • electrons are free or electrons move around or electrons are free to flow or electrons attracted to positive terminal • electrons carry charge / current or electrons form the current / electrons transfer charge / electrons pass charge ignore electrons carry electricity ignore reference to positively charged atoms / ions if they state electrons have +ve charge = max 1 mark if they state covalent bonding then max 1 mark 2 (b) ions can move / are attracted to electrode accept ions are free allow ‘they’ for ions or attracted to named electrode or ions are charged or ions form / carry the current or ions form the charge 1 (c) (i) electron gain ignore hydrogen reduces charge 1 (ii) sodium hydroxide or NaOH or caustic soda do not allow hydroxide alone 1 (iii) 2Cl– ─ 2 e– → Cl2 or 2Cl– → Cl2 + 2 e– allow fractions or multiples allow e or e– do not allow e+ 1 [6] (a) hydrogen for 1 mark 1 (b) chloride ions are negative; negative ions move to positive electrode each for 1 mark 2 (c) any one use of chlorine e.g. sterilisation; bleaching; making plastics any one for 1 mark 1 [4] M8. (i) electrolysis 1 (ii) oxidation 1 (iii) hydroxide ions or OH– accept sodium hydroxide or hydroxide or OH for one mark only 2 (iv) H+ + e– 1 H2 ignore any state symbols 1 2H+ + 2e– → H2 accept H+ + e-→ H for one mark only 1 [7]
