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1 NAME ......................................................................................INDEX NO......................................... SCHOOL ............................................................................. 233/1 CHEMISTRY Paper 1 2 HOURS KHAMULUJONAB JOINT EXAMINATION K.C.S.E. CHEMISTRY TRIAL EXAMS PAPER 1 2 HOURS INSTRUCTIONS Answer all the questions in the spaces provided . Electronic calculators and mathematic tables may be used. FOR EXAMINERS USE ONLY QUESTIONS MAX MARKS 1 – 28 80 STUDENTS SCORE 2 Q. 1 The table below gives atomic and mass number of some elements represented by letters T to Y. The letters are not the actual symbols of elements. Use it to answer the questions that follow. Element Atomic No. Mass No. T 1 2 U 18 39 V 1 1 W 19 39 X 20 40 Y 17 35 a) Which element has the lowest first ionization energy. Explain. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Element V is uniquely positioned into periodic table. It has tendency of forming compounds by either gaining or sharing electrons. Give the formular of the ion of V that is formed when it gains an electron, ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... Q. 2 A certain hydrocarbon contains 82.7% carbon and the rest hydrogen. The formular mass of the compound is 58 g. ( C = 12, H = 1 ) a) Find the Empirical formular of the compound. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... b) Determine the molecular formula of the hydrocarbon. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 3 Q. 3 The diagram below is a set of apparatus used to investigate the reaction that takes place between steam and iron. a) Identify gas x ( 1 Mark ) .................................................................................... b) State and explain the necessary conditions for the reaction to take place. Conditions ( ½ Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... Explanations ( ½ Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... c) Write the equation for the reaction that takes place in the boiling tube. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 4 Q.4. 30 of unknown gas takes 12.6 seconds to pass through a porous material. 10 cm 3 of oxygen gas takes 11.2 seconds to diffuse through the same material at the same condition of pressure and temperature. Calculate the molar mass of the unknown gas. (O=16) ( 3 Marks ) .......................................................................................................................................................................... cm3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Q. 5 Jane placed chlorine water near a window where it was exposed to sunlight. a) Describe what happens to it after sometime. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Write a balanced chemical equation to shown how bleaching powder is prepared. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 6. a) Distinguish between a strong acid and a concentrated acid. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Giving a reason in each case identify an acid and a base in the equation. H3 O+ (aq) + NH3 (g) Acid Reason NH4 + + H2 O (i) ...................................................................................................... ( ½ Mark ) ( ½ Mark ) 5 .......................................................................................................................................................................... .......................................................................................................................................................................... Base ( ½ Mark ) ............................................................................................................... Reason ( ½ Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 7. Draw structures of three main isomers having formula C5 H12 and give their respective IUPAC. ( 3 Marks ) 8. a) Apart from iron ore (haematite) name two other raw materials fed into the blast furnace in the extraction of iron metal. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Write an equation to show how the ore is reduced in the blast furnace, ( 1 Mark ) .......................................................................................................................................................................... 9. Study the nuclear equation below and answer the questions that follow: 6 a) Determine the values of: N ½ mark M ½ mark b) State one useful application of this type of nuclear reactions. .......................................................................................................................................................................... .......................................................................................................................................................................... c) Write an equation to how a Thorium nuclide 228 Th undergoes alpha decay to form 90 another nuclide radium Ra. Clearly indicate the mass number and atomic number of radium. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 10. The table below shows the pH values of some solutions. Solution A pH 12 B 7 C 2 D 5.5 a) Which solution reacts most vigorously with magnesium metal. ( 1 Mark ) ................................................................................... b) which solution forms a complex ion with aluminium oxide. ( 1 Mark ) .................................................................................. c) Which solution is likely to be passion fruit? ( 1 Mark ) ................................................................................. 11. A substance gives a green precipitate when aqueous sodium hydroxide is added to it. When hydrogen peroxide is added to 5, a new substance T gives a reddish-brown precipitate in aqueous sodium hydroxide. a) Give the ions in S and T respectively. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 7 b) Explain the role of hydrogen peroxide using an ionic equation. ( 1 Mark ) .......................................................................................................................................................................... ........................................................................................................................................................................ 12. Use the diagram below to answer the questions that follow The water is normally used at a temperature of at least 155º C. i) Suggest why such a high temperature is used. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... ii) Suggest why the hot water is in the outer most tube. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... iii) The diagram shows the settling tank has two layers. State why are two layers. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 13. Explain why chlorine is termed as one of the green house gases. ( 3 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... 8 14. a) State why a water molecule (H2O) can combine with H+ ions to form H3 O+ ion. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Using dots ( .) and crosses (x) show the structure of the hydroxonium . ( 1 Mark ) 15. Study the flow diagram below. H2 SO4 180 º C Butan-i-oi Process x But-i-ene B Process y C4 H8 CL2 a) Write down the structural formular of butan-i-o1 ( 1 Mark ) .................................................................................................................... b) Name the processes x and y. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 9 c) In which group of the homologous series do the compound A and B belong? ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 16. The diagram below shows a splint of wood that was placed horizontally a cross the middle of a non-luminous flame. a) Explain the observation. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Explain why the non-luminous flame is preferred to heating as compared to luminous flame. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... 17. Carbon (II) oxide gas was passed over heated Lead (II) oxide as shown in the diagram below. 10 a) State any one observation made in the combustion tube. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Why is burning necessary at the jet? ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... c) State one commercial use of carbon (II) oxide. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 18. The paper chromatogram below shows the identification of unknown metal ions in a mixture M. The reference ions X, Y and Z are also shown. The experiment was done in an ascending method. a) Name the ions presenting mixture M. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Indicate the solvent front on the diagram. ( 1 Mark ) ........................................................................................................................................................................ c) Mixture Q contains all the three ions. On the diagram show the chromatogram of Q. ( 1 Mark ) 11 19. The set up below was used to electrolyse dilute sulphuric acid. Use it to answer the questions that follow. a) Label the electrodes. x y - ( 1 Mark ) ......................................................... ......................................................... b) Name the products formed in both electrodes. X Y - ( 1 Mark ) .................................................................. .................................................................. c) Write the equation of the reaction that takes place at Y. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 20. Ammonia burns in oxygen forming nitrogen and water according to the equation. 4 NH 3 (g) + 3 O2 (g) 2N2 (g) + 6 H2O (g) If 80 cm3 of Ammonia are burnt in 100 cm3 of oxygen what will be the total volume of gas after combustion and what will be its composition? Assume that all volumes are measured at r.t.p. ( 2 Marks ) 12 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 21. Lead (II) Sulphate can be prepared by double decomposition. a) What is meant by double decomposition? ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) Starting with Sodium Sulphate solution, describe how you would prepare a pure sample of Lead (II) sulphate. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 22. The table below shows the solubility of potassium nitrate and potassium chlorate at various temperatures. Salt Solubility at various temperature 50ºC 20ºC Potassium nitrate 86 g 31 g Potassium Chlorate 18 g 8g A mixture of salts containing 20 g of Potassium nitrate and 18 g of Potassium Chlorate in 100 g of water at 50 ºC. 13 a) State the method which may be used to separate the mixture. ( 1 Mark ) ........................................................................................................................................ b) If the mixture were cooled from 50 º C to 20 º C; state and explain what would be observed. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... 23. A mass pf 0.2 of methane gas (CH4 ) was used to heat 200 g of water. The temperature of water rose from 21 º C to 34 º C. Calculate the heat change when one mole of methane is used. ( C = 12, H = 1, specific heat capacity = 4.2 J g -1 k -1 ) ( 3 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 24. The equation below shows the formation of methanol from Carbon ( II) oxide and hydrogen gas in equilibrium. CO(g) + 2H2 (g) CH3 OH (g) ∆H= -92 kg/mol a) What effect would the following have on the state of the equilibrium. i) Adding more CO (g) ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... ii) Increase in pressure. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) How would the position of the equilibrium to the affected if the temperature is raised? ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 14 25. Study the figure below and answer questions that follow. After a week some of the iron wool turned to red brown. a) State and explain one other observation that would be made. ( 2 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... b) What would be observed if a large piece of iron wool was used. ( 1 Mark ) .......................................................................................................................................................................... .......................................................................................................................................................................... 26. State and explain the observation made when a lump of sodium metal is put in a beaker of cold water containing a few drops of universal indicator. ( 3 Marks ) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 15 27. The following is a representation of polystyrene polymer H I C I H H I - C I C6H5 H I C I H H I - C I C6H5 a) Draw the monomer unit of polystyrene. b) Calculate the number of monomers used to form polystyrene polymer with a relative molecular mass 36192 ( C = 12, H = 1 ) ( 1 Mark ) 28. State two differences between the bleaching action of sulphur (iv) oxide and chlorine. ( 2 Marks )
