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Chemistry I First Semester Final Review Material Unit I: Introduction to Chemistry Short Answer/Fill in the Blank: Identify the letter of the choice that best completes the statement or answers the question. 1. Chemistry can best be defined as…? __the study of matter and all the changes it may undergo_________________________ 2. Matter is anything that has __mass_______ and __volume________. 3. When writing the problem/statement of an experiment it is always best to write it in the form of a __question________. 4. Must a hypothesis always be proven correct? Explain why or why not. No; hypotheses are educated attempts to explain an observation but they may not explain a scientific observation. 5. What is the purpose of a control group? To provide a comparison of the experimental study to a norm. 6. Rank the three states of matter studied in this unit according to their respective densities. Most dense 1. Solid 2. Liquid Least dense 3. Gas 7. A pure substance that cannot be separated into simpler substance by a chemical change is called a(n) __element___________. A substance that contains two or more elements chemically combined in a fixed proportion is called a(n) ___compound______. 8. ___Distillation_________________ is a mixture separation technique for homogeneous mixtures that utilizes differences in boiling points, while ____filtration____________ can be used to separate heterogeneous mixtures such as sand and water. Completion: Complete the following answers by following the directions given in each question. 9. Fill in the following chart to describe what happens to the shape and volume of each state of matter when the sample is placed into a new container. Shape Volume Gas Takes the shape of the container it is in. Same volume as the container that it is in. Retains shape Maintains its’ original volume. Takes the shape of the container it is in. Will fill the container incompletely. Solid Liquid 10. Give an example of each of the following types of substances. a. Pure substance (element) ____diamond_________ b. Pure substance (compound) ____water____________ c. Homogeneous mixture ____apple juice_______ d. Heterogeneous mixture ____________________ 11. Give one example of each of the following processes. a. Physical change _____tearing paper_______________ b. Chemical change _____digesting of food____________ Short Answer: Answer the following questions, being sure to include appropriate terminology and/or definitions. 12. A student is given an unknown substance for analysis. The substance is an orange liquid and appears to be uniform throughout. What would the student do to determine whether the substance is a mixture or pure substance? If it is a mixture what separation technique could be used to separate the mixture. The student could use distillation or crystallization to separate the possible mixture. 13. What are constants? What is the importance of having constants in an experiment? Constants are variables that are kept the same by the experimenter. They are important so you can see the way the independent variable affects the dependent variable. 14. Describe two (2) ways that chemistry affects your daily life. Answers will vary. Examples: Breathing and digestion of food. 15. What is the relationship between the independent variable and the dependent variable of an experiment. The independent or controlled variable is the variable that affects the dependent or uncontrolled variable in an experiment. 16. A student is given a heterogeneous mixture of two unknown substances. One substance is magnetic and the other substance is not. How might the student easily separate the mixture? Use a magnet to separate the magnetic substance from the non-magnetic substance. 17. What may happen if you do not communicate the results of your experiment to an audience after it has been concluded? The cure for rabies may not be found. 18. Using examples, compare qualitative and quantitative data. Qualitative the candle was longer than the pencil. Quantitative: the candle was 3 inches longer than the pencil. Application: Use the following experiment description to answer questions 19 - 26. A class of students decided to determine how various exercises affect the amount of calories they burn while exercising for a 30 minute period. The amount of calories burned during a 30 minute period was determined by using a heart rate monitor that could calculate the amount of calories burned. Students then performed 5 different exercise routines including weightlifting, running, walking, yoga, and biking. Students began the experiment by measuring the amount of calories burned in a thirty minute period while resting. At the end of the experiment each student shared their results with the other students in order to determine which exercise routine was the most effective. 19. What is the problem for this experiment? Which exercise routine will burn the most calories in a 30 minute period? 20. Write an appropriate hypothesis for this experiment. Running for 30 minutes will burn the most calories when compared to weightlifting, walking, yoga, and biking. 21. What is the independent variable? Exercise activity 22. What is the dependent variable? Calories burned 23. What is the control group? Calories burned during rest 24. Identify 2 constants for the experiment. Answers will vary. Examples: Temperature and clothing. 25. Was the data collected in this experiment qualitative or quantitative? Quantitative 26. After conducting this experiment, Allison concludes that “running is the best exercise.” Would this be an appropriate conclusion for this experiment? Explain your answer. No; although running may burn the most calories it may not be the “best” exercise. Unit II: Chemical Foundations Fill in the Blank: Fill in the blanks with the appropriate term listed below. atom electron atomic number isotope average atomic mass protons nucleus cation anion periods neutrons groups The periodic table organizes elements by putting them in __groups__________ or the elements in a vertical column on the periodic table and by _periods____ which are the elements in a horizontal row on the periodic table. Elements are placed in the periodic table in numerical order according to their ____atomic number_________ , which tells us the number of protons in the nucleus of an element. The ____atom____________ is the fundamental unit of an element. The central core of an atom is the ____nucleus_________, which contains ___protons_______, which are positively charged subatomic particles, and ___neutrons_______, which are subatomic particles with no charge. ____Electrons____ are negatively charged particles that are found outside the nucleus. Atoms can become charged when they gain or lose electrons. A __anion_______ is a negatively charged ion and a ____cation______ is a positively charged ion. When an atom has a different number of neutrons in the nucleus it is then called an ___isotope___. Their presence is what allows us to calculate the ___average atomic mass____ which is our final number on the periodic table. Short Answer: Using a brief statement, answer each of the following questions about atomic structure. 1. John Dalton’s atomic theory states that, “atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.” The underlined portion of this statement is incorrect. Why? Because of the presence of ions and isotopes. 2. How did Rutherford’s model of the atom differ from Thomson’s plum pudding model? Rutherford had a positively charged nucleus at the center of the atom. Thomson had positive charges spread throughout the entire atom. 3. What were two main conclusions of Rutherford’s gold foil experiment? 1. The atom is mostly empty space. 2. At the center of the atom is a dense, positive nucleus. 4. J.J. Thomson used a cathode ray tube to discover which negatively charged subatomic particle? Electron 5. Which scientist built off of Thomson’s work with the electron? What did he determine? Millikan. He determined the mass-to-charge ratio of the electron. 6. What is the atomic number and mass number of an atom of an element with 13 protons and 16 neutrons? Atomic number -13 Mass Number - 29 7. List, in order, from least massive (has the least mass) to most massive (has the most mass) the following particles: hydrogen atom, electron, helium atom, proton Electron; proton; Hydrogen atom; Helium atom 8. What is the name of the number, that is used to identify an element? Atomic number 9. An ion always contains an unequal/equal (circle one) number of protons and electrons/neutrons (circle one). 10. An atom of uranium that contains 92 protons and 143 neutrons would be called: Uranium-235 11. How many protons, neutrons and electrons does a neutral atom of an element with atomic number 50 and mass number 120 contain? Identify the element. Protons – 50; neutrons – 70; electrons - 50 Tin is the element 12. What is the family/group name for the elements in column 6A (16)? Oxygen family/Chalcogens 13. What is the family/group name for the elements in column 4A (14)? Carbon family 14. What is one way that Mendeleev organized his periodic table? Increasing atomic mass or chemical reactivity. 15. How are metals and nonmetals distinguished on the periodic table? Metals are mainly on the left side of the periodic table and non-metals are on the right side of the table. 16. Why are the noble gases called “inert gases”? They do not react. Problems: Solve the following problems in the space provided. Show your work where necessary. 17. Determine the number of protons, neutrons, and electrons in the ion Protons: 23; neutrons: 28; electrons: 20 51 V3+. 23 18. A neutral atom has 10 protons and 11 neutrons in its nucleus. Write out its nuclear symbol. (1.5 points) 21 10 Ne 19. An ion contains 50 protons, 69 neutrons, and 46 electrons. What is its nuclear symbol? 119 50 Sn+4 20. Complete the following table. Symbol # protons # neutrons 112 Cd 48 48 64 79 2Se 34 34 45 189 3Bi 83 83 106 35 1Cl 17 17 18 137 2+ Ba 56 56 81 # electrons Net Charge 48 0 36 2- 86 -3 18 -1 54 2+ Short Answer: Answer the following questions, being sure to include appropriate terminology and/or definitions. 21. Compare and contrast metalloids and non-metals. Metalloids are mainly solids at room temperature and exhibit properties of both metals and non-metals. Non-metals are solids, liquids, and mainly gases at room temperature. 22. List 2 nonmetals from the periodic table (using their symbols) and describe how they may be used. Answers will vary. Examples: Oxygen is used to breathe. Neon is used in lighting. 23. List 2 metals from the periodic table (using their symbols) and describe how they may be used. Answers will vary. Examples: Gold is used in jewelry. Lithium is used in batteries. 24. Are isotopes and ions considered atoms? Why or why not? Yes, they just have a different number of electrons and neutrons. Unit III: Compound Formulas and Nomenclature Questions: Write the correct answer to each question or statement in the space provided. 1. Why do most elements tend to gain or lose electrons when they become involved in the bonding process? To satisfy the octet rule. 2. How many electrons will an atom of any element in the alkali metal family lose when they bond with a non metal? one 3. What is one difference between an ionic compound and a covalent compound? Answers will vary. 4. Which of the following compounds is not ionic: SiCl2 , NaCl, N2O5 , S2F2 5. Which of the following compounds is covalent: NaNO3, CaI2, SO2, RbO 6. During the formation of covalent compounds, electrons are __shared_______ between atoms. An ionic bond forms when electrons are ___transferred_______ from one atom to another. (2 points) 7. Metals will typically _lose_______ electrons to attain a noble gas electron configuration. 8. What are valence electrons and why are they important? (2 points) valence electrons are the outermost electrons and are involved in bond formation 9. What does the octet rule state? Atoms will gain, lose or share electrons in order to attain a complete set of 8. Short Answer: Answer the following questions in complete sentences. 10. Compare and contrast ionic and covalent compounds in terms of their properties and the elements that make up the compounds. Be specific and detailed in your answer. Ionic – metal and nonmetal; electrons are transferred; brittle; high melting points; conduct electricity in water. Covalent – nonmetal and nonmetal; electrons are shared; soft; low melting points; do not conduct electricity in water. 11. What do the prefixes in covalent compounds tell us? Exact number of atoms in the compound. 12. Why do we use roman numerals when naming some ionic compounds but not others? Some metals have multiple charges. The roman numeral tells the charge that the metal has. 13. Give an example of both an empirical formula and a molecular formula. What are the differences between the two? CH2O – empirical (lowest whole number ratio) C6H12O6 – molecular (true formula) Problems: Solve the following problems in the space provided. Show your work. 14. Write the name of each of the following compounds in the space provided. a. Li3PO4 _____lithium phosphate__________________________ b. S2F8 _____disulfur octafluoride________________________ c. Cu(OH)2 _____copper (II) hydroxide_______________________ d. (NH4)2SO4 _____ammonium sulfate__________________________ e. AuF3 _____gold (III) fluoride___________________________ f. N3O6 _____trinitrogen hexaoxide________________________ g. SiO4 _____silicon tetraoxide___________________________ h. Mg(NO3) 2 _____magnesium nitrate__________________________ i. NaCN _____sodium cyanide_____________________________ j. CBr4 _____carbon tetrabromide__________________________ 15. Write the chemical formula that represents each of the following compounds on the space provided. a. silver sulfate _____Ag2SO4_________________________ b. dihydrogen monoxide _____H2O_________________________ c. sodium nitride _____Na3N_________________________ d. lead (III) oxide _____Pb2O3_________________________ e. lithium chloride _____LiCl_________________________ f. manganese phosphate _____Mn3(PO4)2_________________________ g. carbon tetrachloride _____CCl4_________________________ h. nickel (II) cyanide _____Ni(CN)2_________________________ i. iron (II) acetate _____Fe(C2H3O2)2_________________________ j. nitrogen dioxide _____NO2_________________________ Unit IV: Measurements and Calculations Short Answer/Multiple Choice: Circle the letter of the answer that correctly answers the question or completes the sentence. 1. Why is the SI unit for mass the kilogram and not the gram? Because of large items 2. Write the measurement 3.46 x 10-3 g in standard notation. 0.00346 g 3. How many decimeters are in 25 kilometers? 250,000 dm 4. The smallest volume from among the following is a. 0.014 L. b. 1.8 cL. c. 250 mL. d. 1.6 x 10-2 L. 5. What is the SI unit for time? seconds 6. The largest mass from among the following is a. 1.8 g. b. 1.6 x 102 dg. c. 0.012 mg. d. 25 ng. 7. Which of the following statements is true? a. All zeros in numbers are not significant. b. Numbers trapped between non-zero numbers are significant. c. Leading zeros are significant only if a decimal is absent. d. Trailing zeros are never significant. 8. In scientific notation, what does the sign (+/-) of the power of ten indicate? which way to move the decimal 9. What is the rule for an addition and subtraction problem? (How do we determine how many significant digits our answer will have?) Based off of the least precise measurement 10. What is the process of using conversion factors to change from one unit to another called Dimensional Analysis Short Answer: Answer the following questions in complete sentences. 11. What is the purpose of using significant figures in science? Why are they more important to use in science than in math? Significant figures illustrate the uncertainty that every measurement has with it. 12. Why is the metric system considered easier to use than the English system of measurement? Based off of powers of 10. 13. What is wrong with the following number written in scientific notation? 45.68 x 10-6 45.68 is not a number between 1 and 10. It should be 4.568 Problems: Solve the following problems in the space provided. Show your work. 14. Write the following numbers in scientific notation. a. 51,200,000 cm ____5.12 x 107___________ b. 0.0458 mL ____4.58 x 10-2___________ c. 0.000000781 km ____7.81 x 10-7___________ d. 540,000 s ____5.4 x 105___________ 15. Convert the following numbers to standard notation. a. 1.64 x 10-4 m _____0.000164 m_______________ b. 7.2 x 107 dL _____72,000,000 dL_______________ c. 3.25 x 10-2 nm _____0.0325 nm_______________ d. 6.5 x 101 ms _____65 ms_______________ 16. How many significant figures are there in each of the following measurements? a. 34.000 g __5_____ b. 0.0006789 cm __4____ c. 2108.45 km __6_____ d. 0.870 mm __3_____ e. 560. L __3_____ 17. Perform the following operations. Make sure that your answers have the correct number of significant figures. (No Naked Numbers!) a. 26.5 cm x 200.50 cm 5310 cm2 b. 307.506 km – 156 km 152 km c. (4.650 X 109 mm)/ (8.2 X 10-6 s) 5.7 x 1014 mm/s d. 268.500 g + 86.47 g 354.97 g 18. Convert the following metric measurements. (You do not have to show dimensional analysis.) a. 5.0 x 103 mm to km 0.0050 km b. .0257 dL to cL 0.257 cL c. 620 pm to nm .620 nm d. 9.9 kg to cg 990,000 cg 19. A teacher brings his students 36 dozen doughnuts to eat. However, he decides to give 1.5 dozen doughnuts to the office staff. How many total doughnuts does he have left for the students? Show your work in dimensional analysis. 414 doughnuts 20. Perform the following conversion using dimensional analysis: 3.6 days to centiseconds. Show your work in dimensional analysis. 3.1 x 107 cs 21. A student measures her foot to be 5 inches long. How long is her foot in meters? In kilometers? Show your work in dimensional analysis and express your answer to the appropriate number of significant figures. (There are 2.54 cm in one inch.) 0.127 m 1.27 x 10-4 km 22. Convert 25 km/hr to miles/min. (There are 1.609 km in a mile.) 0.26 miles/min Unit V: The Mole Short Answer/ Multiple Choice: When appropriate circle the letter of the answer that correctly answers the question or write a brief answer in your own words. 1. What is the importance of relative mass when determining the average atomic mass of an element? Relative mass is the mass of the individual isotopes multiplied by its abundance and tells how much that isotope contributes to the overall mass. 2. What two things are necessary in order to calculate the average atomic mass of an element? mass of the isotope and percent abundance 3. The molar mass of a compound is defined as…? the mass of one mole of the substance 4. The molar mass of C6H6 (also known as benzene) is a. 125.00 g/mol b. 120.00 g/mol c. 78.00 g/mol d. 72.00 g/mol 5. Representative particles include all of the following EXCEPT… a. formula units b. molecules c. moles d. atoms 6. A mole of tungsten contains 6.02 x 1023 a. formula units. b. molecules. c. moles. d. atoms. 7. A mole of silver nitrate contains 6.02 x 1023 a. formula units. b. molecules. c. moles. d. atoms. 8. It is possible to convert moles to molecules by a. dividing by Avogadro’s number. b. multiplying by Avogadro’s number. c. dividing by molar mass. d. multiplying by molar mass. 9. The percentage composition of CH4 is: a. 75% C, 25% H b. 92% C, 8% H c. 20% C, 80% H d. 25% C, 75% H 10. Which of the following is an empirical formula? a. C6H6. b. H2O2. c. N2O4. d. CH2O. 11. What is the difference between an empirical formula and a molecular formula? Empirical – lowest whole number ratio Molecular – true formula 12. What is the empirical formula of a compound whose molecular formula is C10H22O12? a. CH12O2 b. C20H44O24 c. C5H11O6 d. C4H2O3 13. How are one mole of Mercury and one mole of Iron similar? How are they different? (2 points) same number of atoms; different masses 14. Match the representative particles to its’ correct partner by connecting them with a line. (3 points) i. Covalent compounds a. atoms ii. Ionic compounds b. formula units iii. Elements c. molecules Problems: Solve the following problems in the space provided. Show your work for full credit! 15. The substance Teflon, the nonstick coating on many frying pans, is made from the C2F4 molecule. Calculate the number of C2F4 units present in 135 g of Teflon. (4 points) 8.13 x 1023 molecules 16. Element X has two naturally occurring isotopes. They have masses of 34.9689 amu and 36.9659 amu, with percent abundances of 75.78% and 24.22% respectively. What is the average atomic mass of element X? Identify element X. (4 points) 35.45 amu Chlorine 17. Fat makes up a major portion of all soaps. A fat used in many soaps is 76.5% carbon, 12.2% hydrogen, and 11.3% oxygen. What is its empirical formula? (5 points) C9H17O 18. How many moles of phosphorus pentabromide are present in 225.7 g of the compound? (3 points) 0.5237 mol 19. Strychnine, a deadly poison, has a molecular mass of 334 amu and a percentage composition of 75.42% carbon, 6.63% hydrogen, 8.38% nitrogen, and the balance oxygen. What is the molecular formula of strychnine? (6 points) C21H22N2O2