CHEMISTRY 10A/E September 3, 010 T. Hummel NAME SIGNATURE SECTION SAMPLE This exam is made up of an answer sheet, two cover sheets and 7 numbered pages. Below are instructions for coding the answer sheet. At the bottom of this sheet are the solubility rules. Cover sheet ii, attached to the back of this exam, contains some useful equations and constants, plus the periodic table. On the answer sheet: 1. Use # pencil. Erase cleanly.. Print your NAME in the appropriate designated spaces, then blacken in the letter boxes below each printed letter, last name first, then your first name initial. 3. Fill in your university ID number under STUDENT NUMBER. 4. Under SECTION write the five digit number that corresponds to your section designation, and then blacken in the corresponding number of boxes. For 10A students, the numbers are: AQ1 = 00011, AQ = 0001, AQ3 = 00013, AQ4 = 00014, AQ5 = 00015, AQ6 = 00016, AQ7 = 00017, AQ8 = 00018, AQ9 = 00019, AQA = 0001, AQB = 000, AQJ = 0003. For 10E students, the numbers are: EQ1 = 00051, EQ = 0005, EQ3 = 00053, EQ4 = 00054, EQ5 = 00055, EQ7 = 00057, EQ8 = 00058, EQA = 00061, EQB = 0006, EQC = 00063, EQD = 00064, EQE = 00065. 5. Under NETWORK ID print your University Network ID beginning on the left hand side with box #1, and then blacken in the corresponding letters, numbers and/or dashes under each character. Do not fill in a character for any unused boxes. 6. Under TEST FORM blacken the letter corresponding to the form designated on the upper left hand corner of the exam booklet. 7. Your TA's name should be printed for INSTRUCTOR and write your section number for SECTION in the lines provided. 8. Sign your name (do not print) on the line provided. 9. Mark only one answer per question and do not use the answer sheet for scratch paper or make any stray marks on it. Erase cleanly if you wish to change an answer. The exam itself can be used for scratch paper. Work carefully and efficiently. If your answer differs from one given in the last proper significant figure, mark that answer as correct and not the response "none of these". All questions are worth the same. Page 5
1. My answers for this Chemistry 10 exam should be graded with the answer sheet associated with: a) Form A b) Form B c) Form C d) Form D e) Form E. Consider the measurements 9.74 m and 0.59 m. If one adds these measurements together, one should record the answer to significant figures, and if one multiplies these measurements together, one should record the answer to significant figures. a) 3, 3 b) 4, 3 c) 3, d) 4, e), 3. Which of the following statements is false? a) In general, there are fewer nonmetals than metals in the periodic table. b) Metals tend to form stable anions when in ionic compounds. c) Ammonium nitrate is an example of an ionic compound. d) Potassium fluoride contains an alkali metal and a halogen. e) Water is an example of a covalent compound. 4. The neutral atoms of all the isotopes of the same element have: a) the same number of electrons. b) equal numbers of neutrons. c) different numbers of protons. d) the same mass number. e) none of these is correct. 5. At STP, 35. L of H gas is reacted with 5.3 L of O gas to produce H O gas. After the reaction, the H O gas is removed. What volume of H O gas at STP can be produced? a) 17.6 L b) 50.6 L c) 5.3 L d) 70.4 L e) 35. L 6. SO is produced when substances containing sulfur (coal) are burned. SO released into the atmosphere reacts to form sulfuric acid according to the equation: SO (g) + O (g) + H O(l) H SO 4 (l) What mass of H SO 4 (molar mass = 98.09) can be produced if 64.0 g O and 19 g SO are combined with excess water? a) 98.1 g b) 147 g c) 196 g d) 94 g e) 39 g Page 6
7. In your Chem 103 laboratory, you find a mystery aqueous solution on the shelf. The solution may contain one or more of the following cations: Ni +, Ag +, Ca +, Mn +. In order to determine the contents you add the following solutions: addition of excess aqueous hydrochloric acid causes a precipitate to form. The precipitate is removed, and excess aqueous potassium sulfate is added and another precipitate forms. The precipitate is removed, and aqueous sodium hydroxide is added to the solution; no precipitate forms upon addition of aqueous sodium hydroxide. Which ion/ions were present in the original mystery solution? a) Ag + only b) Ni + and Ca + c) Ag + and Ca + d) Mn + and Ni + e) Ni +, Ag +, Ca +, Mn + 8. Which of the following compounds is named incorrectly? a) Li 3 N: lithium nitride b) ICl: iodine monochloride c) Cu(NO 3 ) : copper(ii) nitrate d) H S: sulfuric acid e) FePO 4 : iron(iii) phosphate 9. An actual yield of 3.00 g of aspirin (molar mass = 180.15 g/mol) are prepared in a laboratory according to the following equation. C 7 H 6 O 3 (aq) + C 4 H 6 O 3 (aq) C 9 H 8 O 4 (s) + H O(l) salicylic acetic aspirin acid anhydride If the percent yield of the reaction is 70.0% and salicylic acid (molar mass = 138.1 g/mol) is in excess, what mass of acetic anhydride (molar mass = 10.09 g/mol) was used in the experiment? a) 0.850 g b).30 g c) 1.1 g d) 3.9 g e) 0.595 g 10. Consider an element E. If.00 g of E reacts exactly with 10.1 g of chlorine to form a compound with the formula ECl 4, what is the identity of E? a) Cl b) Si c) P d) Al e) Ge Page 7
11. You are holding two balloons each filled with the same mass of gas. One balloon contains Ne gas and the other balloon contains Ar gas. Which of the following statements concerning these two balloons is true? Assume constant temperature. a) The balloon filled with Ar gas and the balloon filled with Ne gas will have equal volumes. b) The balloon filled with Ne gas will be about twice as large as the balloon filled with Ar gas. c) The Ar balloon has an internal pressure which is about twice the pressure inside the Ne balloon. d) The balloon filed with Ar gas will be about twice as large as the balloon filled with Ne gas. e) The Ne balloon has an internal pressure which is about twice the pressure inside the Ar balloon. 1. A sample of gas containing 0.50 moles of CO at 5C exerts a pressure of 0.75 atm. More CO gas is added to the container and the temperature is raised to 50. C. The resulting pressure is.5 atm. How many moles of CO were added to the container? Assume that the gas is ideal and that the container volume remains constant. a) 1.0 moles b) 0.33 moles c) 1.5 moles d) 0.83 moles e) 0.50 moles 13. Consider the combustion of the organic compound camphor, C 10 H 16 O. What is the sum of the coefficients of all the reactants and products in the best balanced equation? a) 65 b) 31 c) 40 d) 57 e) 63 14. Upon detonation trinitrotoluene (TNT) decomposes according to the following reaction: C 7 H 5 N 3 O 6 (s) 3 N (g) + 5 H O(g) + 7 CO(g) + 7 C(s) 0.750 mol of C 7 H 5 N 3 O 6 is initially placed in a 10.0 L container at 50.C. Calculate the total pressure exerted by the gases in the 10.0 L container after all the TNT decomposes to products. Assume a constant temperature of 50.C. a) 4.1 atm b) 3. atm c) 35.4 atm d) 6.44 atm e) 11.5 atm Page 8
15. Which of the following statements is false? a) Aqueous solutions are also called homogeneous mixtures. b) A compound has constant composition. c) Chunky salsa is an example of a heterogeneous mixture. d) Potassium is an example of a pure substance. e) Compounds can be converted to elements through a physical change. 16. How many nitrogen atoms are present in 5.00 g of calcium nitride? a).03 10 atoms of nitrogen b) 9.97 10 atoms of nitrogen c) 3.3 10 atoms of nitrogen d) 6.09 10 atoms of nitrogen e) 4.06 10 atoms of nitrogen 17. When magnesium nitrate reacts with sodium hydroxide, a precipitate forms. Which of the following is the correct net ionic equation for the precipitation reaction? a) Na + (aq) + NO 3 (aq) NaNO 3 (s) b) Mg + (aq) + OH (aq) MgOH(s) c) Na + (aq) + OH (aq) Na(OH) (s) d) Mg + (aq) + OH (aq) Mg(OH) (s) e) Mg + (aq) + OH (aq) Mg OH(s) 18. If 50.0 ml of 0.00 M magnesium nitrate is added to 00.0 ml of 0.300 M sodium hydroxide, how many moles of precipitate will form assuming the reaction has a percent yield of 100%? a) 0.0300 mol b) 0.0100 mol c) 0.0600 mol d) 0.00500 mol e) 0.000 mol 19. If 50.0 ml of 0.00 M magnesium nitrate is added to 00.0 ml of 0.300 M sodium hydroxide, what is the concentration of hydroxide ions after the reaction has gone to completion? a) 0.300 M b) 0.40 M c) 0.160 M d) 0.0800 M e) 0.0 M Page 9
0. How many of the following five compounds (I-V) are strong electrolytes? I. HC H 3 O II. CH 3 OH III. (NH 4 ) CO 3 IV. HNO 3 V. FeCO 3 a) one b) two c) three d) four e) five (all) 1. A compound has the empirical formula CH O. If the density of the gaseous compound is 1.50 g/l at 15C and 413 torr, what is the molecular formula of the compound? a) CH O b) C H 4 O c) C 3 H 6 O 3 d) C 4 H 8 O 4 e) C 5 H 10 O 5. Which of the following statements best describes the significance of Rutherford s alpha particle bombardment experiment? a) Rutherford s experiment confirmed Thomson s plum pudding model of the atom. b) Rutherford showed that atoms contain particles that are neutral charged. c) Rutherford s experiment confirmed that the positive charge of the atom is uniformly distributed throughout the atom. d) Rutherford s experiment indicated that the nucleus of an atom contains the negative charge. e) Rutherford s experiment indicated that most of the mass of an atom is contained in the tiny dense nucleus. 3. The diffusion rate of N gas is 1.73 times greater than the diffusion rate of a certain noble gas (both gases are at the same temperature). What is the noble gas? a) He b) Ne c) Ar d) Kr e) Xe 4. Which of the following three statements about gases is/are true? I. Equal masses of ideal gases at the same temperature and pressure contain equal numbers of molecules. II. On average, a N molecule will possess the same kinetic energy as a CO molecule at the same temperature. III. On average, an H molecule has a faster average velocity than a N molecule at the same temperature. a) I and II b) II and III c) I and III d) I, II, and III e) Only statement I is true. Page 10
5. Identify the stable isotope which has a mass number of 185 and whose +3 ion has 7 electrons. a) 185 7 Hf b) 188 7 Hf c) 185 75 Re d) 188 75 Re e) 185 69 Tm 6. How many of the following four statements (I-IV) about gases is/are true? I. A non-ideal gas will more nearly behave like an ideal gas at low pressures. II. Non-ideal gas behavior is the result of the real volume of gas particles and the intermolecular attractions between gas particles. III. The effect of attractive forces between gas particles can be reduced by heating the gas. IV. 1.00 10 3 gas molecules placed in a closed 5.0 liter container at 150. K would behave more ideally than the same number of molecules placed in a closed 50.0 liter container at the same temperature. a) 0 (none) b) 1 c) d) 3 e) 4 (All of the statements are true.) 7. Caffeine consists of carbon, hydrogen, oxygen, and nitrogen. When 0.190 g of caffeine is burned in an excess of oxygen, 0.348 g of carbon dioxide, 0.0891 g of water, and some nitrogen gas are formed. From the nitrogen gas produced, it was determined that caffeine is 8.84% nitrogen by mass. What is the mass percent of hydrogen in caffeine? a) 5.19% H b) 3.0% H c) 1.7% H d).60% H e) 8.7% H 8. Caffeine consists of carbon, hydrogen, oxygen, and nitrogen. When 0.190 g of caffeine is burned in an excess of oxygen, 0.348 g of carbon dioxide, 0.0891 g of water, and some nitrogen gas are formed. From the nitrogen gas produced, it was determined that caffeine is 8.84% nitrogen by mass. What is the empirical formula for caffeine? a) C 4 H 5 N O b) C 3 H 3 N O c) C 4 H 5 N O d) C 4 H 10 N 4 O 4 e) C H 5 N O Page 11
9. Consider the reaction of aluminum reacting with oxygen to form aluminum oxide. What mass of aluminum oxide can be produced when 0.0 g of Al is reacted with excess oxygen? a) 8. g b) 19.8 g c) 37.8 g d) 75.6 g e) 10.0 g 30. A 1.80 g sample of a metal iodide, MI, is dissolved in water and treated with excess aqueous silver nitrate, AgNO 3. After drying, the silver iodide that formed weighed.106 g. Calculate the molar mass of M. The molar mass of silver iodide is 34.8 g/mol. a) 40.7 g/mol b) 76.0 g/mol c) 15.0 g/mol d) 304.0 g/mol e) 111.5 g/mol 31. The following equation describes the chemical reaction used by the bombardier beetle as a defensive measure. C 6 H 4 (OH) (aq) + H O (aq) C 6 H 4 O (aq) + H O(l) The enthalpy change for the reaction is 0.6 kj. Which of the following statements (ac) is/are true? a) The reaction is exothermic. b) The reaction is endothermic. c) Energy is released as the reaction occurs. d) Both statements a and c are correct. e) Both statements b and c are correct. 3. In the titration of a 4.05 ml sample of commercial vinegar (d = 1.0 g/ml) with 1.0 M NaOH solution, it required 56.0 ml of the NaOH solution to react with all of the acetic acid in the vinegar. What is the mass percent of acetic acid in the vinegar? Acetic acid is a monoprotic acid and has a molar mass of 60.05 g/mol. a) 1.63% b) 3.6% c) 5.40% d) 6.5% e) 9.41% 33. An unknown ion forms a compound with perchlorate having the molecular formula XClO 4. The unknown ion has 36 electrons. What is the identity of the unknown element X? a) Kr b) K c) Sr d) Ca e) Rb Page 1
USEFUL INFORMATION K = C + 73 PV = nrt 1 kg = 1000 g R = 0.0806 L atm/k mol 1 L = 1000 ml Avogadro's number, N = 6.0 10 3 1 atm = 760 torr = 760 mm Hg Mass % of A = rate1 rate M M P measured 1 mass of A(100) total mass (M an V molar mass) (V measured nb) nrt M = Molarity = % yield = actual theoretical mol solute L solution P total = P 1 + P + P 3 +... STP = 1 atm, 73 K (100) d = density = mass/volume PM = drt, M = molar mass P1 V n T 1 1 1 PV n T KE AVE = (3/) RT, R = 8.3145 J/Kmol Kinetic Energy = (1/) mv Solubility rules: 1. Most nitrate salts are soluble.. Most salts of alkali metals and ammonium cations are soluble. 3. Most chloride, bromide and iodide salts are soluble. Exceptions: salts containing Ag +, Pb + and Hg + ions are insoluble. 4. Most sulfate salts are soluble. Exceptions: sulfates containing Ca +, Ba +, Pb + and Hg + ions are insoluble. 5. Most hydroxide salts are insoluble. Exceptions: hydroxides containing alkali metals, Ba +, Sr + and Ca + ions are soluble. 6. Most sulfide, carbonate, chromate and phosphate salts are insoluble. Exceptions: salts of alkali metals and ammonium cations are soluble. Page 13