Gases

Gases & the Kinetic-Molecular Theory

1. Kirsten is in her lab, and reacts two unknown gases (A(g) and B(g)) to get nitrogen dioxide (NO2). Using her data, she is able to write the following balanced equation:

2A(g) + B(g) --> 2NO2(g)

If she started with 8 L of A(g) and 3 L of B(g), how many liters of NO2(g) would she get? [Assume everything is at STP.]

a. 2 L b. 3 L c. 4 L d. 6 L e. 8 L

2. Calculate the number of kilograms of O2(g) that can be stored in a compressed gas chamber with a volume of 40 L when the cylinder is filled at 150 atm and 21oC.

a. 4.0 kg b. 8.0 kg c. 4000 kg d. 8000 kg e. Not enough information

3. Yesterday, Jason had a sample of helium indoors (T = 23oC) in a sealed container, with a pressure of 760 mm Hg. He got bored and took the container outside, where the temperature was a blistering 35oC. He calculated the new pressure to be 750 mm Hg. Jason knew that this answer was not correct because:

a. TK = ToC + 273.15

b. Equal volumes of gas have the same number of moles. c. P is proportional to n d. P is proportional to T e. He forgot to convert his temperature to K and the pressure should have decreased

even more. 4. Suppose that Quebec had managed to succeed from Canada and became an independent

country. Just to be difficult, they decreed that they will only measure pressure in mm Hg and volume in cm3. What value for R, the ideal gas constant, would students in Quebec use when solving the ideal gas solution?

a. 7.6 x 105 b. 6.23 x 104 c. 8.14 d. 2.78 e. 0.082

5. Consider two 1 L flasks, one containing O2, the other containing He, each at STP. Which of the following statements is NOT true regarding these gases?

a. Each flask contains the same number of atoms or molecules

b. The gases in each flask have the same average kinetic energy c. The gases in each flask have the same density d. The pressure in each flask is the same e. The temperature of the gases in each flask is 273.15 K.

6. The density of N2 at STP is:a. 1.25 g/L b. 1.04 g/L c. 0.625 g/L d. 0.0625 g/L e. 5.43 mg/L

7. A 1.00 L flask containing 450 torr of H2 is connected to and mixed with a second flask with a volume of 0.500 L containing 250 torr N2. What is the final pressure of the resulting mixed gas system?

a. 250 torr b. 383 torr c. 450 torr d. 575 torr e. it cannot be determined

8. A piston is used to compress a gas from 1.0 atm to 3.5 atm. If the volume changes from 1.5 L to 0.75 L, what is the final temperature, if it started at 300 K?

a. 1050 K b. 700 K c. 525 K d. 300 K e. 150K

9. 2.00 g of sucrose is combusted in excess oxygen. What is the volume of dry CO2 that is formed at 1 atm pressure and 37oC? (MW sucrose = 342.3 g/mol)

C12H22O11 + 12O2 --> 12CO2 + 11H2O

a. 22.4 L b. 10.4 L c. 1.78 L d. 0.545 L e. 0.148 L

10. Which of the following statements regarding the kinetic-molecular theory of ideal gases is incorrect?

a. gas molecules collide elastically b. gases molecules are in random motion c. the average kinetic energy is constant if T is constant d. the kinetic energy of all the molecules is the same e. attractive and repulsive forces can be neglected

11. Which of the following graphs does NOT correctly illustrate the ideal gas law?

12. The ideal gas law asserts that when two other variables are held constant:a. n and V are inversely proportional. b. n and T are directly proportional. c. P and V are directly proportional. d. n and T are inversely proportional. e. P and T are inversely proportional.

13. What volume would a weather balloon containing 105 liters of helium at STP occupy if the temperature fell to -90.0oC and the pressure fell to 8.45 torr (as it must in the upper atmosphere)?

a. 0.783 L b. 8.33 L c. 6330 L d. 9450 L e. 14100 L

14. A balloon is filled with He to a pressure of 1.06 atm. The volume of the balloon at 25oC is 1.30 x 104 L. How many cylinders of He gas are needed to fill the balloon if the pressure in the cylinder at 20oC is 98.5 atm and the volume of the cylinder is 40.0 L. [You may have some He left in one of the cylinders.]

a. 1 b. 2 c. 3 d. 4 e. 5

15. A sample of nitrogen dioxide gas occupies 76.3 mL at 35oC and 765 mm Hg. The density of the nitrogen dioxide is:

a. 0.546 g/L b. 1.39 g/L c. 1.83 g/L d. 18.2 g/L e. 24.0 g/L

16. The density of CH4 gas at 0oC and P = 1 atm is four times that of gas X at the same T, P. X could be:

a. H2 b. He c. O2 d. C4H16 e. The identity of X cannot be determined from the given information.

17. Nitrogen gas escapes through a pinhole in 68.4 seconds. Under the same conditions, a gaseous compound with the empirical formula CH2 escapes in 83.8 seconds. What is its molecular formula?

a. CH2 b. C2H4 c. C3H6 d. C4H8 e. C5H10

18. You have 3 identical balloons at room temperature. You inflate each one to the same size, filling them with different gases. You put helium in balloon 1, nitrogen in balloon 2, and xenon in balloon 3. You realize that the pressure inside each balloon is equal to atmospheric pressure. You notice that balloon 1 floats to the ceiling, balloon 2 feels light, and balloon 3 feels heavy. Which balloon contains the most gas particles?

a. Balloon 1 b. Balloon 2 c. Balloon 3 d. Balloons 1 and 3 have equal numbers and more than Balloon 2 since nitrogen

atoms are bonded to each other. e. All 3 balloons have the same number of gas particles.

19. A quantity of 73.0 g of NH3(g) is mixed with an equal mass of HCl(g). What is the volume of the gas remaining (i.e., NH3 or HCl) measured at 14oC and 752 mm Hg after the reaction has gone to completion?

NH3(g) + HCl(g) --> NH4Cl(s)

a. 47.7 L HCl b. 51.0 L HCl c. 54.3 L NH3 d. 102 L NH3 e. No gas remains since equal masses react.

20. A gas mixture at 25oC and a total pressure at 1.00 atm contains 1.03 g of each of the following gases: H2, He, N2, CO2. Which has the highest molecular speed?

a. H2 b. He c. N2 d. CO2 e. All have the same speed since all are at the same temperature in the same

container. 21. 16 g of O2 are mixed with 16 g of He in a container. The total gas pressure is 1.0 atm.

The partial pressure of O2 is:a. 0.11 atm b. 0.13 atm c. 0.5 atm d. 0.89 atm e. The partial pressure cannot be determined because the temperature and volume of

the container are not given. 22. At 20oC the rms speed of methane, CH4, produced by Indiana cows is approximately:

a. 300 m/s b. 700 m/s c. 5 x 105 m/s d. 10 m/s e. 20 m/s

23. Van der Waals constant, a, that appears in the relationship

corrects for:

a. the average speed of the gas molecules. b. the density of gas molecules. c. variation in the gas constant, R. d. the volume occupied by the gas molecules. e. the attractive forces between gas molecules.

24. A balloon contains 14.0 L of air at a pressure of 760 torr. What will the volume of the air be when the balloon is taken to a depth of 10 ft in a swimming pool, where the pressure is 981 torr? The temperature of the air in the balloon does not change.

a. 8.8 L b. 17.7 L c. 15.4 L d. 5.4 L e. 10.8 L

25. A sample of freon gas used in an air conditioner has a volume of 325 L and a pressure of 96.3 kPa at 20oC. What will be the pressure of the gas when its volume is 975 L at 20oC?

a. 289 kPa b. 32.1 kPa c. 105 kPa

d. 96.3 kPa e. 75.4 kPa

26. A particular hydrogen gas thermometer has a volume of 150.0 cm3 when immersed in a mixture of ice and water (0.00oC). When immersed in boiling liquid ammonia, the volume of the hydrogen, at the same pressure, is 131.7 cm3. What is the temperature of the boiling ammonia?

a. -33oC b. 38oC c. 0.00oC d. 235oC e. -77oC

27. Methane, CH4, can be used as a fuel for an automobile; however, it is a gas at normal temperatures and pressures, which causes a problem with storage. One gallon of gasoline could be replaced by 655 g of CH4. What is the volume of this much methane at 25oC and 745 torr? [At. Wts: C = 12.01 amu; H = 1.008 amu; 3.79 L = 1.00 gallon]

a. 9.55 gal b. 175 gal c. 269 gal d. 1002 gal e. 2515 gal

28. A hydrocarbon (containing the elements carbon and hydrogen) is commonly used as an anesthetic. If a 2.00 L flask contains 3.11 g of the hydrocarbon gas at 684 torr and 23oC, what is the molecular formula of the hydrocarbon? [At. Wts: C = 12.01 amu; H = 1.008 amu]

a. C5H10 b. C2H6 c. C2H4 d. C4H10 e. C3H6

29. What is the total pressure in atmospheres in a 10.0 L vessel containing 2.50 x 10-3 mol of H2, 1.00 x 10-3 mol of He, and 3 x 10-4 mol of Ne at 35oC?

a. 1.10 atm b. 2.75 x 10-2 atm c. 8.76 x 10-4 atm d. 3.80 x 10-3 atm e. 9.61 x 10-3 atm

30. A balloon contains 4.70 x 10-2 mol O2 and 8.87 x 10-2 mol N2 at a total pressure of 1.00 atm. What is the partial pressure of O2 in the balloon?

a. 0.65 atm b. 0.35 atm c. 0.95 atm d. 2.86 atm e. 0.23 atm

31. A gas of unknown identity diffuses at the rate of 83.3 mL/s in a diffusion apparatus in which a second gas, whose molecular weight is 44.0 amu, diffuses at the rate of 102 mL/s. What is the molecular weight of the first gas?

a. 66.0 amu b. 40.4 amu c. 34.2 amu d. 22.4 amu e. 10.2 amu

32. Which of the following statements is not true?a. The pressure of a real gas is greater than or equal to the pressure calculated for an

ideal gas. b. The volume of a real gas is greater than or equal to the volume calculated for an

ideal gas. c. The van der Waals equation helps to calculate the pressure and volume of real

gases. d. Real gas molecules do occupy a finite, but small, volume. e. Real gas molecules experience intermolecular forces.

33. The "a" term in the van der Waals equation arises because:a. real gas molecules occupy a finite volume. b. at high pressures the observed pressure is greater than the ideal pressure. c. the average kinetic energy of gas molecules is proportional to temperature in

Kelvin. d. real gas molecules experience intermolecular forces. e. the volume of real gas depends on root-mean-square velocity.

34. An atmospheric chemist isolates a gaseous pollutant. At STP she determines that the density of the gas is 2.14 g/L. What is the identity of the pollutant?

a. NO b. NO2 c. O3 d. SO2 e. SO3

35. In lecture, the composition of air was given to be by volume 78% N2, 21% O2, and 1% other. If the total pressure of air inside a sealed container is 2.0 atm, what is the partial pressure of the O2?

a. 0.10 atm b. 0.21 atm c. 0.42 atm d. 1.0 atm e. 2.0 atm

36. Consider these identical flasks filled with three different gases:

Flask A CO at 760 torr and 0.0oC

Flask B N2 at 250 torr and 0.0oC

Flask C H2 at 100 torr and 0.0oC

37. In which flask will the molecules have the greatest average kinetic energy?a. Flask A

b. Flask B c. Flask C d. All three have the same average kinetic energy. e. Not enough information.

38. Which of the following assumptions of the kinetic molecular theory of gases is not valid for real gases at high pressure?

a. The volume of the gas particles is much smaller than the distance between the gas particles.

b. The gas particles behave like hard, spherical objects in a state of constant, random motion.

c. The average kinetic energy of the gas particles depends upon temperature of the gas only.

d. Collisions between gas particles are perfectly elastic. No energy of a gas particle is lost when it collides.

e. The gas particles move in a straight line until they collide with another particle or the walls of the container.

39. A gas sample occupies 400 mL at a pressure of 2.00 atm. What is the volume if the pressure is changed to 20 atm at constant temperature?

a. 4000 mL b. 20 mL c. 40 mL d. 800 mL e. 8000 mL

40. What is the volume (L) occupied by 2.19 moles of methane gas (CH4) at 298 K and 1 atm?

a. 0.0186 b. 4.5 c. 11.2 d. 49.2 e. 53.6

41. Which of the following is not a postulate of kinetic-molecular theory of gases?a. Gases consist of large numbers of molecules in constant random motion. b. Attractive and repulsive forces between gas molecules are negligible. c. The volume of all the molecules of the gas is negligible. d. Gas molecules collide frequently, and collisions are perfectly elastic. e. At a given temperature, a gas with low molar mass has less kinetic energy than a

gas with high molar mass. 42. 2.00 moles of Cl2 gas at 20oC is heated to 350oC while the volume is kept constant. The

density of the gasa. increases. b. decreases. c. remains the same. d. cannot be determined.

43. Calculate the ratio of effusion rates of O2 and H2:a. rate O2/rate H2 = 1/16 b. rate O2/rate H2 = 32/1

c. rate O2/rate H2 = 1/4 d. rate O2/rate H2 = 16/1 e. rate O2/rate H2 = 4/1

44. A mixture of three gases has a total pressure of 1388 torr at 298 K. If the mixture contains 1.27 mol Cl2, 3.04 mol CO, and 1.50 mol Ar, what is the partial pressure (torr) of Ar?

a. 196 b. 301 c. 358 d. 5345 e. 8020

45. Deviation from the ideal gas law is greatest at:a. low temperature and low pressure. b. low temperature and high pressure. c. high temperature and high pressure. d. high temperature and low pressure.

46. Molecules of different gases have the same average kinetic energies at the samea. pressure. b. temperature. c. volume. d. density.

47. A gas has a volume of 175 L at 760 torr and 288 K. What is the temperature if the gas volume and pressure are changed to 198 L and 640 torr?

a. 547 K b. 487 K c. 387 K d. 274 K e. 214 K

48. The SI unit of pressure isa. pascal b. torr c. atm d. mm Hg e. joule

49. What is the molar mass of Freon gas if its density is 6.13 g/L at STP?a. 0.274 g/mol b. 3.64 g/mol c. 78.2 g/mol d. 137 g/mol e. 365 g/mol

50. Which gas has molecules with the greatest average molecular speed at 25oC?a. CH4 b. Kr c. N2 d. CO2 e. Ar

51. A 5.0 L volume of a certain gas weighs 289 mg. If the mass was measured at a pressure of 540 torr and a temperature of 27oC, what is the identity of the gas?

a. H2 b. He c. N2 d. Ar e. CO2

52. What is the density of Xe gas (MW=131.3 g/mol) in a 1.0 L flask at 100oC and 2.0 atm pressure?

a. 0.065 g/L b. 0.65 g/L c. 8.6 g/L d. 15.4 g/L e. 131 g/L

53. Molecular speed distributions for a gas at two different temperatures are shown below. Which of the following graphs correctly describes the distributions at the two temperatures, where T2 > T1? [Note: the small vertical lines indicate average speed]

54. Which of the following graphs is inconsistent with ideal gas behavior?

55. Two separate glass bulbs, bulb A and bulb B, are both filled with helium. The pressure in bulb A is twice that of bulb B. The volume of bulb B is twice that of bulb A. What can be said about these two systems if they are held at the same temperature?

a. Bulb A has more atoms of helium in it than bulb B. b. Bulb B has more atoms of helium in it than bulb A. c. Bulb B and bulb A contain the same number of atoms of helium. d. The densities of the gases in both bulbs are the same since they are filled with the

same gas. e. More information is needed to make any of these conclusions.

56. The system below is a two dimensional representation of a gas. What happens to the gas if it is placed into the container on the right (assuming both containers are at the same temperature)?

a. The density of gas would increase. b. The density of gas would decrease. c. The number of gas molecules would increase. d. The mean or average molecular speed of the gas molecules would decrease. e. None of the above describe what would happen.

57. An inflated balloon has a volume of 6.0 L at sea level (1.0 atm). It is allowed to ascend in altitude until the pressure is 0.45 atm. During ascent the temperature of the gas falls from 22oC to -21oC. Calculate the volume of the balloon at its final altitude.

a. 0.6 L

b. 1.1 L c. 6.0 L d. 11 L e. 12 L

58. The volume of a 1 mole sample of propane gas at 50 atm pressure and 100oC is measured, and the quantity PV/RT is found to be significantly smaller than 1.00. The explanation for this is:

a. the propane must be above its critical temperature. b. the propane molecules attract one another. c. the volume of the propane molecules cannot be neglected. d. propane is an incompressible gas. e. hydrogen bonding influences the properties of propane.

59. Which graph best represents the distribution of molecular speeds for the gases argon and methane, CH4, when both are in the same flask with a total pressure of 600 mm Hg and a partial pressure of 450 mm Hg for the argon? [Note: The vertical lines on each curve represents the root mean square velocity.]

60. A gas phase reaction takes place in a syringe at a constant temperature and pressure. If the initial volume is 40 cm3and the final volume is 60 cm3, which general reaction took place?

a. A(g) + B(g) --> AB(g) b. 2A(g) + B(g) --> A2B(g) c. 2AB2(g) --> A2(g) + 2B2(g) d. 2AB(g) --> A2(g) + B2(g) e. 2A2(g) + 4B(g) --> 4AB(g)

61. Air (assume 100% N2) effuses out of a tire in 2.5 minutes. How long would it take for the same volume of xenon (at the same T,P) to effuse out of the tire?

a. 61 min b. 12 min c. 5.4 min d. 1.2 min e. 0.53 min

62. Chemical analysis of a gaseous compound showed that it contained 33.0% Si and 67.0% F by mass. At 35oC, 0.210 L of the compound exerted a pressure of 1.70 atm. If the mass of 0.210 L of the compound was 2.40 g, determine its molecular formula.

a. SiF4 b. SiF3 c. Si2F8 d. Si2F6 e. Si3F9

63. Which of the following gases has a density of 0.714 g/L at STP? a. He b. CH4 c. CO d. CO2 e. Cl2

64. What is the partial pressure of H2 in a mixture of 10.0 g H2 and 10.0 g N2 for which the total pressure is 5.00 x 102 torr? [AW: H = 1.01; N = 14.01]

a. 34 torr b. 2.50 x 102 torr c. 4.66 x 102 torr d. 5.00 x 102 torr e. the question cannot be answered because the temperature is not given.

65. Under conditions of standard temperature and pressure, what volume of O2(g) is necessary to react with 2.0 L of NO(g) to give 3.0 L of a product mixture containing only NO2(g) and O2(g)?

a. 1.0 L b. 1.5 L c. 2.0 L d. 2.5 L e. 3.0 L

66. A balloon is to be filled with helium until the volume at a presure of 1.00 atm is 2.00 x 104 L. The temperature is 300 K. The helium is stored in pressurized cylinders each with a volume of 50.00 L and a He pressure of 150 atm at 300 K. How many cylinders are needed to fill the balloon (the He in the last cylinder may not be used up completely)?

a. 2 b. 3 c. 4 d. 400 e. 812

67. If a 2.0-L vessel contains 0.5 mol Ar at 298 K, the gas pressure in atm is:

a. 6.1 atm b. 0.51 atm c. 240 atm d. 1.0 atm e. 75 atm

68. A sample of an unknown gas is placed in a 1.50-L bulb at a pressure of 356 torr, a temperature of 22.5oC, and is found to weigh 0.9847 g. What is the molecular weight of the gas?

a. 34.0 b. 64.0 c. 17.0 d. 38.0 e. 76.0

69. If all else is constant, which of the following steps will double the volume of an ideal gas?

a. halve the pressure b. double the absolute temperature c. remove half the molecules d. a and b only e. a, b and c

70. Which of the following statements concerning the kinetic theory of gases is(are) correct?

I. Molecules make elastic collisions with each other and with the walls of their container.

II. The average kinetic energy of a large number of molecules of mass, M, is proportional to M1/2 at a given temperature.

III. The molecules of a gas are in constant random motion. IV. All the molecules of a gas have the same kinetic energy at a given temperature.

e. I, II, III, IV f. I, II, III g. I, III, IV h. I, III i. only III

71. The average temperature at an altitude of 20 km is 220 K. What is the rms speed (in meters per second) of N2 molecules at this altitude?

a. 5 m/s b. 55 m/s c. 111 m/s d. 221 m/s e. 443 m/s

72. The rms speed of O2 molecules is 5.0 x 102 m/s at a certain temperature. The rms speed of H2 molecules at the same temperature is:

a. 8.0 x 103 m/s b. 2.0 x 103 m/s c. 5.0 x 102 m/s

d. 1.3 x 102 m/s e. 3.1 x 101 m/s

73. O2 gas escapes through a pinhole in 37.5 seconds. Under the same conditions, the same volume of another gas escapes in 44.0 seconds. This gas could be:

a. He b. CO c. Cl2 d. F2 e. CO2

74. 20 g of H2 gas are mixed with 20 g of He gas in a container. The total gas pressure is 1.0 atm. The partial pressure of H2 is:

a. 1.0 atm b. 0.67 atm c. 0.50 atm d. 0.33 atm e. The partial pressure cannot be determined because the temperature and volume of

the container are not given. 75. The following volume-temperature plots were made at different values of constant

pressure and constant number of moles of gas. Which plot represents measurements at the highest pressure?

a. A b. B c. C d. D e. none of the above

76. Compare the root mean square speed of a O2 molecule with that of a CH4 molecule at the same temperature and pressure.

a. O2 is 2.5 times faster since it has 2 atoms per molecule while CH4 has 5. b. The speeds are the same since the weights of O2 and of CH4 are both 16 g/mol. c. The speeds are the same because at the same temperature all gas molecules have

the same root mean square speed. d. CH4 is 2.00 times faster because the M.W. of O2 is 2.00 times greater than the

molecular weight of CH4.

e. CH4 is 1.41 times faster since at equal temperature all gas molecules have the same kinetic energy. The root mean square speed then is inversely proportional to the square root of the molecular weight.

77. What is the volume of a scuba tank if it takes 2000 L of air collected at 1 atm to fill the tank to a pressure of 150 atm?

a. 500 L b. 2.07 L c. 8.80 L d. 13.3 L e. 3.00 x 105 L

78. Calculate the partial pressure of propane in a mixture that contains equal weights of propane (C3H8) and butane (C4H10) at 20oC and 746 mm Hg. [At Wts: C = 12.01 amu; H = 1.008 amu]

a. 424 mm Hg b. 212 mm Hg c. 646 mm Hg d. 322 mm Hg e. 196 mm Hg

79. If it takes 6.5 seconds for 25.0 cm3 of helium gas to effuse through a pinhole into a vaccum, how long would it take 25.0 cm3 of CH4 to escape under the same conditions? [At Wts: He = 4.003 amu; C = 12.00 amu; H = 1.008 amu]

a. 13.0 s b. 3.25 s c. 26.2 s d. 1.82 s e. 10.1 s

80. Calculate the density of helium which is at 0.00oC and 1.00 atm. Report your answer in units of g/L.

a. 0.00 g/L b. 0.0146 g/L c. 0.0446 g/L d. 0.178 g/L e. not enough information

81. A gas initially at 4.00 atm has a volume of 8.00 L. What is the pressure required to compress the gas to a volume of 2.00 L?

a. 4.00 atm b. 2.00 atm c. 1.00 atm d. 8.00 atm e. 16.0 atm

82. How many moles of gas occupy 60.82 L at 31oC and 0.483 atm?a. 1.18 b. 0.850 c. 894 d. 11.6 e. 0.120

83. A mixture of two gases, A and B, has a total pressure of 0.95 atm and contains 0.32 moles of gas A and 0.56 moles of gas B. What is the partial pressure (in atm) of gas B?

a. 1.7 b. 1.5 c. 0.60 d. 0.35 e. 0.56

84. The kinetic molecular theory of gases predicts pressure to rise as the temperature of a gas increases because

a. the average kinetic energy of the gas molecules decreases b. gas molecules collide more frequently with the container walls c. gas molecules collide less frequently with the container walls d. gas molecules collide less energetically with the container walls e. both (b) and (d)

Answers

1. D 2. B 3. D 4. B 5. C 6. A 7. B 8. C 9. C 10. D 11. D 12. D 13. C 14. D 15. C 16. B 17. C 18. E 19. C 20. A 21. A 22. B 23. E 24. E 25. B 26. A 27. C

28. E 29. E 30. B 31. A 32. A 33. D 34. C 35. C 36. D 37. A 38. C 39. E 40. E 41. C 42. C 43. C 44. B 45. B 46. D 47. A 48. D 49. A 50. A 51. C 52. A 53. A 54. C 55. B 56. D 57. B 58. C 59. C 60. C 61. D 62. B 63. C 64. C 65. B 66. A 67. A 68. D 69. D 70. E 71. B 72. E 73. B

74. A 75. E 76. D 77. A 78. A 79. D 80. E 81. A 82. C 83. B