Chemistry 1310 Exam 3 Past Paper PDF, March 22, 2024

DO NOT BEGIN UNTIL INSTRUCTED TO DO SO Exam 3 Questions are on front and back of each page (Total = 26) Scrap paper and periodic Table/Equation sheet on back may be removed Cheating is a form of academic dishonesty and will not be tolerated. This includes but is not limited to the use...

DO NOT BEGIN UNTIL INSTRUCTED TO DO SO Exam 3 Questions are on front and back of each page (Total = 26) Scrap paper and periodic Table/Equation sheet on back may be removed Cheating is a form of academic dishonesty and will not be tolerated. This includes but is not limited to the use of unauthorized materials and knowingly providing or obtaining unauthorized assistance from another student. Any form of academic dishonesty will result in a zero on the exam and possible expulsion from the course. !!!All materials must be turned in at the conclusion of the exam!!! Chemistry 1310 March 22, 2024  Version A 1. A 0.512-g sample of an unknown pure gas occupies a volume of 0.777 L at a pressure of 1.00 atm and a temperature of 373 K. What is the unknown gas? a) krypton b) neon c) helium d) xenon e) argon 2. To what temperature must a balloon filled with argon, initially at 282 K and 4.00 L, be heated to have a volume of 6.00 L? a) 366 K b) 423 K c) 578 K d) 629 K e) 691 K 3. A large balloon is initially filled to a volume of 25.0 L at 353 K and a pressure of 3.39 atm with nitrogen gas (MWN2 = 28.01 g/mol). What volume of N2 will the balloon contain at 1.35 atm and 253 K? a) 22.2 L b) 58.6 L c) 11.4 L d) 87.5 L e) 45.0 L 4. How many milliliters of a 9.0 M H2SO4 (MWH2SO4 = 98.08 g/mol) solution are needed to make 0.25 L of a 3.5 M solution? a) 0.097 mL b) 160 mL c) 0.64 mL d) 640 mL e) 97 mL 5. At a given temperature, the vapor pressures of hexane (MWC6H14 = 86.18 g/mol) and toluene (MWC7H8 = 92.14 g/mol) are 183 mmHg and 59.2 mmHg, respectively. Calculate the total vapor pressure over a solution of hexane and toluene if the mole fraction of hexane is 0.580. a) 131 mmHg b) 121 mmHg c) 242 mmHg d) 106 mmHg e) 178 mmHg 6. Calculate the freezing point of a solution containing 50 grams of KCl (MWKCl = 74.55 g/mol) and 5500.0 grams of water (MWH2O = 18.02 g/mol). The molal-freezing-point-depression constant for water is 1.86 C/m. a) -1.23 C b) -0.45 C c) +0.45 C c) -0.23 C e) +0.23 C 7. The boiling point of an aqueous 1.83 m (NH4)2SO4 (MW(NH4)2SO4 = 132.15 g/mol) solution is 102.5 C. Determine the value of the van't Hoff factor for this solute if the Kb for water (MWH2O = 18.02 g/mol) is 0.512 C/m. a) 1.8 b) 3.0 c) 2.7 d) 2.3 e) 3.6 8. Place the following solutions in order of increasing osmotic pressure. I. 0.15 M C2H6O2 II. 0.15 M CaCl2 III. 0.15 M LiBr a) I < II < III b) II < I < III c) I < III < II d) III < I < II e) II < III < I 9. Which of the following compounds would you expect to be weak electrolyte? a) NH4Cl b) Ca(NO3)2 c) MgSO4 d) BeS e) KC2H3O2 10. Which compound is most soluble in octane? a) KNO3 b) CH3OH c) H2O d) NH3 e) CBr4 11. At 1 atm, how many moles of CO2 (MWCO2 = 44.01 g/mol) are released by raising the temperature of 1 liter of water from 20 C to 25 C? a) 0.0030 mol b) 0.0040 mol c) 0.0050 mol d) 0.0060 mol e) 0.0070 mol 12. A solution is saturated in both oxygen gas and potassium chlorate at 348 K. When the solution is heated to 388 K, what is most likely to happen? a) Some oxygen gas bubbles out of solution and some additional potassium chlorate will dissolve. b) Some oxygen gas bubbles out of solution and some potassium chlorate precipitates out of solution. c) Some potassium chlorate precipitates out of solution. d) Additional oxygen gas will dissolve. e) Nothing happens. 13. Calculate the density of xenon (MWXe = 131.29 g/mol) gas at a pressure of 0.976 atm and a temperature of 318 K. a) 1.96 g/mL b) 4.91 g/mL c) 0.588 g/mL d) 2.33 g/mL e) 3.81 g/mL 14. A gas mixture in a container at 305 K and 2.00 atm contains 1.56 mol of Ne (MWNe = 20.18 g/mol) and 2.22 mol of Ar (MWAr = 39.95 g/mol). Calculate the partial pressure of Ne in the container. a) 0.355 atm b) 1.56 atm c) 0.703 atm d) 0.825 atm e) 1.41 atm 15. Calculate the root mean square velocity of chlorine gas at 310 K. a) 330 m/s b) 470 m/s c) 10 m/s d) 15 m/s e) 1.5 m/s 16. Two identical vessels are filled, at the same temperature and pressure, with different gases. One is filled with hydrogen and the other with carbon dioxide. Which statement is correct? a) Carbon dioxide molecules have higher average kinetic energy than hydrogen molecules. b) The carbon dioxide molecules are moving faster than the hydrogen molecules. c) Hydrogen molecules have higher average kinetic energy than the carbon dioxide molecules. d) The hydrogen molecules are moving faster than the carbon dioxide molecules. e) The hydrogen molecules and the carbon dioxide molecules have the same average speed. 17. In an effusion experiment, it was determined that nitrogen (MWN2 = 28.01 g/mol) gas effused from a container in 10.00 s, while it took an unknown gas 18.12 s to effuse from the same container. What is the molar mass of the unknown gas? a) 20.80 g/mol b) 28.00 g/mol c) 70.90 g/mol d) 32.00 g/mol e) 91.98 g/mol 18. In general, which of the following gases would you expect to behave the most ideally even under extreme conditions? a) N2 b) CO c) H2 d) H2O e) CCl4 19. Under what conditions of temperature and pressure are gases most likely to behave ideally? a) low temperature and low pressure b) high temperature and low pressure c) high temperature and high pressure d) low temperature and high pressure e) gases always behave ideally 20. What is the molarity of Br− in 0.110 M CaBr2 (MWCaBr2 = 199.89 g/mol)? a) 0.110 M b) 0.0550 M c) 0.330 M d) 1.10 M e) 0.220 M 21. A solution was prepared by dissolving 35.0 g of KCl (MWKCl = 74.55 g/mol) in 225 g of water (MWH2O = 18.02 g/mol). Calculate the mass percent of KCl in the solution. a) 15.9 % b) 10.6 % c) 13.5 % d) 8.51 % e) 16.8 % 22. A solution was prepared by dissolving 35.0 g of KCl (MWKCl = 74.55 g/mol) in 225 g of water (MWH2O = 18.02 g/mol). Calculate the mole fraction of the ionic species KCl in the solution. a) 1.62×10−2 b) 2.62×10−2 c) 3.62×10−2 d) 4.62×10−2 e) 5.62×10−2 23. A solution was prepared by dissolving 35.0 g of KCl (MWKCl = 74.55 g/mol) in 225 g of water (MWH2O = 18.02 g/mol). Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL. a) 0.952 M b) 1.96 M c) 1.03 M d) 2.53 M e) 2.88 M 24. A solution was prepared by dissolving 35.0 g of KCl (MWKCl = 74.55 g/mol) in 225 g of water (MWH2O = 18.02 g/mol). Calculate the molality of KCl in the solution. a) 0.754 m b) 1.03 m c) 1.32 m d) 1.65 m e) 2.09 m 25. A solution is an equimolar mixture of two volatile components A and B. Pure A has a vapor pressure of 50 torr and pure B has a vapor pressure of 100 torr. The vapor pressure of the mixture is 75 torr. What can you conclude about the relative strengths of the intermolecular forces between particles of A and B (relative to those between particles of A and those between particles of B)? a) The intermolecular forces between particles A and B are stronger than those between particles of A and those between particles of B. b) The intermolecular forces between particles A and B are weaker than those between particles of A and those between particles of B. c) The intermolecular forces between particles A and B are the same as those between particles of A and those between particles of B. d) The intermolecular forces between particles A and A are stronger than those between particles of B and B. e) Nothing can be concluded about the relative strengths of intermolecular forces from this observation. 26. Determine the vapor pressure of an aqueous solution (MWH2O = 18.02 g/mol) of the nonvolatile solute, C2H6O2, (MWC2H6O2 = 62.068 g/mol) where the mole fraction of C2H6O2 is, C2H6O2 = 0.0504. The vapor pressure of pure water at the relevant temperature, 298 K, is 23.8 torr. a) 3.76 torr b) 22.6 torr c) 20.0 torr d) 1.23 torr e) 12.5 torr Useful Constants and Relationships 𝐸 = ℎ𝜈 𝐾𝐸 = 𝐸𝑙𝑖𝑔ℎ𝑡 − 𝛷 NA = 6.022 x 1023 mol-1 ℎ 𝜆𝑑𝑒 = R = 0.08206 (L atm)/(mol K) 𝑚v ℎ R = 8.314 J/(mol K) 𝛥𝑥 × 𝑚∆v ≥ 4𝜋 1 L atm = 101.3 J 1 1 1 8 = −ℛ ( 2 − 2 ) c = 2.998 x 10 m/s 𝜆 𝑛𝑓 𝑛𝑖 h = 6.626 x 10-34 J s 1 W = 1 J/s ℛ = 1.097 × 107 𝑚−1 𝑃𝑎 = 𝜒𝑎 𝑃𝑡𝑜𝑡𝑎𝑙 3𝑅𝑇 𝑢𝑟𝑚𝑠 = √ 𝑀 𝐶𝑖 𝑉𝑖 = 𝐶𝑓 𝑉𝑓 𝑛𝑠𝑜𝑙𝑣𝑒𝑛𝑡 𝑃𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 𝑃° 𝑛𝑠𝑜𝑙𝑣𝑒𝑛𝑡 + 𝑖 ∙ 𝑛𝑠𝑜𝑙𝑢𝑡𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑋𝐴 𝑃°𝐴 + 𝑋𝐵 𝑃°𝐵 𝛱 = 𝑖 ∙ 𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 × 𝑅𝑇 ∆𝑇 = 𝑖 ∙ 𝑚𝑜𝑙𝑎𝑙𝑖𝑡𝑦 ∙ 𝐾 𝑎𝑛2 (𝑃 + 𝑉2 ) (𝑉 − 𝑛𝑏) = 𝑛𝑅𝑇 𝑞 = 𝐶∆𝑇 ∆𝐸 = 𝑞 + 𝑤 𝑤 = −𝑃∆𝑉 𝐻 = 𝐸 + 𝑃𝑉 𝑞 = 𝑛∆𝐻 𝑃2 −∆𝐻𝑣𝑎𝑝 1 1 𝑙𝑛 = ( − ) 𝑃1 𝑅 𝑇2 𝑇1 c = λν