Dr. Rogers Chapter 5 Homework Chem 111 Fall 2003 From textbook: 7-33 odd, 37-45 odd, 55, 59, 61 1. Which gaseous molecules (choose one species) effuse slowest? A. SO 2 (g) B. Ar(g) C. NO(g) D. Ne(g) E. CO 2 (g) 2. Consider the following gases at constant temperature: O 3, NO, SO 2, and Ar. Rank the gases with respect to their average molecular speed, the fastest moving on the left. A. NO> Ar > O 3 > SO 2 B, SO 2 > O 3 > Ar > NO C. SO 2 > O 3 > NO > Ar D. Ar > NO > O 3 > SO 2 E. O 3 > SO 2 > NO > Ar 3. The time required for 0.010 moles of SO 3 (g) to effuse through an opening was 22 s. Under the same conditions, an unknown gas required 30 s. The unknown gas is probably A. SiF 4 (g) B. SF 4 (g) C. CF 4 (g) D. SF 6 (g) E. PF 5 (g) 4. At 25 C the molecules of an unknown gas travel four times slower on the average as helium atoms at the same temperature. What is the molar mass of the unknown gas? 5. An unknown gas X effuses 1.65 times faster than C 3 H 8. What is the molar mass of gas X? 6. Consider N 2 and CO 2. Which gas will effuse more rapidly? What will be the ratio of the rates of effusion of N 2 to CO 2? 7. Carry out the following unit conversions: A. 615 torr to KPa B. 1.26 atm to torr C. 740 torr to atm D. 738 torr to mm Hg E. 1.45 KPa to torr
8. A gas sample has a volume of 9.8 L at 720 torr. If the temperature is constant, what volume does the gas sample have at 1.5 atm? 9. The pressure of a gas in a rigid container at 18.0 C is 135 kpa. What is the pressure of the gas at 85.0 C? 10. A gas has a volume of 255 ml at 725 torr. What volume will the gas occupy at 365 torr if the temperature of the gas does not change? 11 A gas has a volume of 3.86 L at a temperature of 45 C. What will the volume of the gas be if its temperature is raised to 80 C while its pressure is kept constant? 12. A sample of a gas has a pressure of 850 torr at 285 C. To what Celsius temperature must the gas be heated to double its pressure if there is no change in the volume of the gas? 13. A sample of helium at a pressure of 740 torr and in a volume of 2.58 L was heated from 24.0 to 75.0 C. The volume of the container expanded to 2.81 L. What was the final pressure in torr of the helium? 14. What must be the new volume of a sample of nitrogen (in L) if 2.68L at 745 torr and 24 C is heated to 375 C under conditions that let the pressure change to 760 torr? 15. A 2.50-L sample of neon has a pressure of 1.59 atm at 45.0 C. What volume would the sample have if the pressure is 725 Torr and the temperature 22.0 C? 16. Which of the following gases are at the same temperature and pressure? All the containers are non-rigid and have the same volume. 17. A 5.00-L sample of xenon gas has a pressure of 155 Torr at 90 C. What mass of Xe is present?
18. What is the pressure (in KPa) of 10.0 g of nitrogen gas in a container of volume 3.00 L at a temperature of 88.0 C? 19. What is the volume (in L) of 20.0 g of oxygen gas at 39 C and 2.13 atm? 20. What mass of carbon monoxide will exert the same pressure as 10.0 g of chlorine gas in the same container under the same conditions? 21. A 1.00-L sample of a gas at 705 Torr and 47 C has a mass of 0.988 g. The gas is A. CO B. CO 2 C. CH 4 D. CF 4 E. Cl 2 22. What is the molar volume of nitrogen at 300. C and 0.500 atm? 23. What mass of sulfur dioxide will exert the same pressure as 50.0 mg of carbon dioxide in the same container under the same conditions? 24. How many molecules of N 2 (g) occupy 1.50mL at 25 C and 15.0 Torr? 25. What volume of CO 2 (g) at 25 C and 760 Torr is produced when 1.00 kg of calcium carbonate is used to neutralize a sulfuric acid spill? The equation for the reaction is CaCO 3 (s) + H 2 SO 4 (aq) CaSO 4 (s) + CO 2 (g) + H 2 O(l) 26. Air bags used in automobiles are rapidly filled with nitrogen gas by the reaction below. 6NaN 3 (s) + 2Fe 2 O 3 (s) 3Na 2 O 2 (s) + 4Fe(s) + 9N 2 (g) How many moles of NaN 3 are required to produce 40.0 L of N 2 (g) at 20 C and 800 Torr? 27. Standard temperature and pressure, STP, refer to
A. 0 C and 1 atm B. 0 C and 202 kpa C. 25 C and 1 atm D. 0 C and 1 Pa E. 298 K and 760 Torr 28. The volume of 2.81 g of an unknown gas is 2.25 L at STP. What is the molar mass of the gas? 29. Calculate the volume of carbon dioxide produced at STP by the combustion of 1.25 moles of propane, C 3 H 8 (g). 30. Which of the following gases has the lowest density at STP? A. methane, CH 4 B. argon C. fluorine D. nitrogen E. ozone, O 3 31. A gas mixture contains 0.0500 moles of hydrogen, 0.0400 moles of carbon dioxide, and 0.0325 moles of nitrogen in a 2.00 L flask. If the total pressure in the flask is 1000 Torr, what is the partial pressure of carbon dioxide? 32. A 750-mL sample of nitrogen was collected by displacement of water from a container at 30 C and an atmospheric pressure of 742 Torr. If the vapor pressure of water at 30 C is 31.8 Torr, calculate the number of moles of nitrogen gas produced. 33. Consider the gas ethylene, C 2 H 4 (g) at 500.0 ml and 25.0 C. Calculate the pressure of 1 mole of ethylene using the van der Waals equation and the ideal gas equation. The van der Waals constants for ethylene are a = 4.47 L 2 atm/ mol 2 and b = 0.057 L/ mol. Explain the results. Answers: 1. A 2. A 3. D 4. 64 g/ mol 5. 16.2 g/mol 6. N 2 effuses 1.25 faster than CO 2 7A) 82.0 kpa B) 958 torr C) 0.974 atm D) 738 mm Hg E) 10.9 torr 8. 6.2 L 9. 166 kpa 10. 507 ml 11. 4.28 L 12. 843 C 13. 796 torr 14. 5.73 L 15. 3.87 L 16. N 2 and H 2 O 17. 8.92 g 18. 183 kpa 19. 7.51 L 20. 3.95 g 21. A
22. 94.0 L 23. 72.8 mg 24. 7.29 10 17 molecules 25 244 L 26. 1.163 Mol NaN 3 27. A 28. 28.0 g mol 29. 84.0 L 30. A 31. 0.430 atm 32. 0.0282 mol 33. 48.9 atm for ideal and 46.3 atm for non ideal