Chem 1411 Exam 3. A.1.9 mm mineral oil B.15 mm mineral oil C.32 mm mineral oil D.380 mm mineral oil E.440 mm mineral oil

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1 Chem 1411 Exam 3 Student: 1. Mineral oil can be used in place of mercury in manometers when small pressure changes are to be measured. What is the pressure of an oxygen sample in mm of mineral oil if its pressure is 28.5 mm Hg? (d of mineral oil = 0.88 g/ml; d of Hg = 13.5 g/ml) A.1.9 mm mineral oil B.15 mm mineral oil C.32 mm mineral oil D.380 mm mineral oil E.440 mm mineral oil 2. A flask containing argon gas is connected to a closed-ended mercury manometer. The closed end is under vacuum. If the mercury level in the closed arm is 230. mm above that in the arm connected to the flask, what is the argon pressure, in torr? A B.230. C.530. D.790. E.none of these choices is correct 3. The air pressure in a volleyball is 75 psi. What is this pressure in torr? A.520 torr B.562 torr C.3900 torr D.7600 torr E torr 1

2 4. "The volume of an ideal gas is directly proportional to its absolute temperature at constant pressure and number of moles" is a statement of Law. A.Charles's B.Boyle's C.Amontons's D.Avogadro's E.Dalton's 5. Which of the lines on the figure below is the best representation of the relationship between the volume of a gas and its pressure, other factors remaining constant? A.a B.b C.c D.d E.e 6. A sample of the inert gas krypton has its pressure tripled while its temperature remained constant. If the original volume is 12 L, what is the final volume? A.4.0 L B.6.0 L C.9 L D.36 L E.48 L 2

3 7. A sample container of carbon monoxide occupies a volume of 435 ml at a pressure of 785 torr and a temperature of 298 K. What would its temperature be if the volume were changed to 265 ml at a pressure of 785 torr? A.182 K B.298 K C.387 K D.489 K E.538 K 8. A 750-mL sample of hydrogen exerts a pressure of 822 torr at 325 K. What pressure does it exert if the temperature is raised to 475 K at constant volume? A.188 torr B.562 torr C torr D torr E torr 9. Nitrogen dioxide is a red-brown gas that is responsible for the color of photochemical smog. A sample of nitrogen dioxide has a volume of 28.6 L at 45.3 C and 89.9 kpa. What is its volume at STP? A.21.8 L B.27.6 L C.29.6 L D.37.6 L E.153 L 10. A sample of nitrogen gas is confined to a 14.0 L container at 375 torr and 37.0 C. How many moles of nitrogen are in the container? A mol B.2.27 mol C.3.69 mol D.206 mol E.227 mol 3

4 11. Ima Chemist found the density of Freon-11 (CFCl 3 ) to be 5.58 g/l under her experimental conditions. Her measurements showed that the density of an unknown gas was 4.38 g/l under the same conditions. What is the molar mass of the unknown? A.96.7 g/mol B.108 g/mol C.127 g/mol D.165 g/mol E.175 g/mol 12. What is the pressure in a 7.50-L flask if 0.15 mol of carbon dioxide is added to 0.33 mol of oxygen? The temperature of the mixture is 48.0 C. A atm B atm C.1.69 atm D.3.96 atm E.4.80 atm 13. An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99 C. The barometric pressure is 753 torr. If the mass of the liquid retained in the flask is g, what is its molar mass? A.20.4 g/mol B.40.9 g/mol C.112 g/mol D.154 g/mol E.184 g/mol 14. Lithium oxide is an effective absorber of carbon dioxide and can be used to purify air in confined areas such as space vehicles. What volume of carbon dioxide can be absorbed by 1.00 kg of lithium oxide at 25 C and 1.00 atm? Li 2 O(aq) + CO 2 (g) Li 2 CO 3 (s) A.687 ml B.819 ml C.687 L D.819 L E.22.4 L 4

5 15. Which of the following gases will be the slowest to diffuse through a room? A.methane, CH 4 B.hydrogen sulfide, H 2 S C.carbon dioxide, CO 2 D.water, H 2 O E.neon, Ne 16. At what temperature in Kelvin is the root mean square speed of helium atoms (atomic weight = 4.00) equal to that of oxygen molecules (molecular weight = 32.00) at 300. K? A.37.5 K B.75 K C.106 K D.292 K E K 17. Freon-12, CF 2 Cl 2, which has been widely used in air conditioning systems, is considered a threat to the ozone layer in the stratosphere. Calculate the root-mean-square velocity of Freon-12 molecules in the lower stratosphere where the temperature is -65 C. A.20 m/s B.120 m/s C.210 m/s D.260 m/s E m/s 18. A system that does no work but which transfers heat to the surroundings has A.q < 0, E > 0 B.q < 0, E < 0 C.q > 0, E > 0 D.q > 0, E < 0 E.q < 0, E = 0 5

6 19. A system which undergoes an adiabatic change (i.e., q = 0) and does work on the surroundings has A.w < 0, E = 0 B.w > 0, E > 0 C.w > 0, E < 0 D.w < 0, E > 0 E.w < 0, E < A system receives 575 J of heat and delivers 425 J of work. Calculate the change in the internal energy, E, of the system. A.-150 J B.150 J C.-l000 J D.1000 J E.575 J 21. A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate E in J. A J B.-420 J C.420 J D.2130 J E J 22. A system initially has an internal energy E of 501 J. It undergoes a process during which it releases 111 J of heat energy to the surroundings, and does work of 222 J. What is the final energy of the system, in J? A.168 J B.390 J C.612 J D.834 J E.cannot be calculated without more information 6

7 23. A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of atm. The value of w, in J, is A.-4.0 J B.4.0 J C.-405 J D.405 J E J 24. Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction? A. H < 0, process is exothermic B. H > 0, process is exothermic C. H < 0, process is endothermic D. H > 0, process is endothermic E. H = 0, since cold packs are sealed 25. A Snickers candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kj? A kj B.29 kj C kj D kj E kj 26. Your favorite candy bar, Gummy Beakers, contains J of energy while your favorite soft drink, Bolt, contains J. If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt, what percent of your 2000 Calorie daily food intake is left for broccoli, beans, beef, etc.? A.53% B.47% C.27% D.11% E.0% 7

8 27. Which of the following is not a state function? A.internal energy B.volume C.work D.pressure E.enthalpy 28. Calculate q when 28.6 g of water is heated from 22.0 C to 78.3 C. A kj B.1.61 kj C.6.74 kj D.9.37 kj E kj 29. If, as a pioneer, you wished to warm your room by taking an object heated on top of a pot-bellied stove to it, which of the following 15-pound objects, each heated to 100 C, would be the best choice? The specific heat capacity (in J/(g K)) for each substance is given in parentheses. Iron (0.450), copper (0.387), granite (0.79), gold (0.129), water (4.18). A.iron B.copper C.granite D.gold E.water 30. Ethylene glycol, used as a coolant in automotive engines, has a specific heat capacity of 2.42 J/(g K). Calculate q when 3.65 kg of ethylene glycol is cooled from 132 C to 85 C. A kj B.-420 kj C.-99 kj D kj E kj 8

9 31. A 275-g sample of nickel at l00.0 C is placed in ml of water at 22.0 C. What is the final temperature of the water? Assume that no heat is lost to or gained from the surroundings. Specific heat capacity of nickel = J/(g K) A.39.6 C B.40.8 C C.61.0 C D.79.2 C E.82.4 C 32. The Starship Enterprise is caught in a time warp and Spock is forced to use the primitive techniques of the 20th century to determine the specific heat capacity of an unknown mineral. The 307-g sample was heated to 98.7 C and placed into a calorimeter containing 72.4 g of water at 23.6 C. The heat capacity of the calorimeter was 15.7 J/K. The final temperature in the calorimeter was 32.4 C. What is the specific heat capacity of the mineral? A J/(g K) B J/(g K) C J/(g K) D J/(g K) E.none of these choices is correct 9

10 Chem 1411 Exam 3 Key 1. (p. 180) E 2. (p. 181) B 3. (p. 182) C 4. (p. 184) A 5. (p. 183) E 6. (p. 189) A 7. (p. 188) A 8. (p. 188) D 9. (p. 188) A 10. (p. 191) A 11. (p. 193) B 12. (p. 196) C 13. (p. 195) D 14. (p. 199) D 15. (p. 205) C 16. (p. 204) A 17. (p. 204) C 18. (p. 227) B 19. (p. 227) E 20. (p. 230) B 21. (p. 230) B 22. (p. 230) A 23. (p. 232) D 1

11 24. (p. 233) D 25. (p. 230) C 26. (p. 230) B 27. (p. 231) C 28. (p. 236) C 29. (p. 235) E 30. (p. 236) B 31. (p. 236) A 32. (p. 236) C 2

12 Chem 1411 Exam 3 Summary Category # of Questions Difficulty: E 17 Difficulty: H 2 Difficulty: M 13 Silberberg Gases Silberberg Thermochemistry

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