Q: A sample of gas occupies 3.50 L at 0.750 atm. If the pressure is increased to 1.50 atm at constant temperature, what is the new volume?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.750 \times 3.50}{1.50} = 1.75\ \text{L}$$

Q: A 0.896 L sample of helium gas is heated from 0°C to a final temperature at constant pressure. If the initial temperature is 273 K, what is the final temperature in Kelvin if the volume increases to 1.20 L?

$$T_2$$ = \frac{$$V_2$$ $$T_1$$}{$$V_1$$} = \frac{1.20 \times 273}{0.896} = 366\ \text{K}$$

Q: A mixture of gases contains O$$_2 at 0.622 $$bar and N$$_2 at 0.517 $$bar at 292 K. What is the total pressure of the mixture?

$$P_{\text{total}} = P_{O_2$} + P_{N_2$} = 0.622 + 0.517 = 1.139\ \text{bar}$$

Q: Which of the following best describes the relationship between the rate of effusion and molar mass according to Graham's law?

$$\text{Rate} \propto \frac{1}{\sqrt{M}}$$

Q: A gas sample at 292 K contains O$$_2 at 0.622 $$bar and N$$_2 at 0.517 $$bar. If the total pressure is 1.139 bar, what is the mole fraction of O$$_2$$?

$$x_{O_2$} = \frac{P_{O_2$}}{P_{\text{total}}} = \frac{0.622}{1.139} = 0.546$$

Q: A mixture of gases is collected over water at 25°C with a total pressure of 758.2 Torr. If the vapor pressure of water at 25°C is 23.770 Torr, what is the partial pressure of the collected hydrogen gas?

$$P_{H_2$} = P_{\text{total}} - P_{H_2O} = 758.2 - 23.770 = 734.4\ \text{Torr}$$

Question 1

Which of the following best explains why air moves into the lungs during inhalation?

Accepted Answer

The pressure inside the lungs becomes lower than the external pressure, causing air to flow in.

Question 2

A sample of gas occupies 3.50 L at 0.750 atm. If the pressure is increased to 1.50 atm at constant temperature, what is the new volume?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.750 	imes 3.50}{1.50} = 1.75\ 	ext{L}$$

Question 3

Which equation correctly relates pressure, force, and area for a gas?

Accepted Answer

$$P = \frac{F}{A}$$

Question 4

At standard temperature and pressure (STP), what is the molar volume of an ideal gas?

Accepted Answer

$$22.7\ 	ext{L/mol}$$

Question 5

A 0.896 L sample of helium gas is heated from 0°C to a final temperature at constant pressure. If the initial temperature is 273 K, what is the final temperature in Kelvin if the volume increases to 1.20 L?

Accepted Answer

$$T_2$$ = \frac{$$V_2$$ $$T_1$$}{$$V_1$$} = \frac{1.20 	imes 273}{0.896} = 366\ 	ext{K}$$

Question 6

Which of the following statements about the kinetic molecular theory is correct?

Accepted Answer

Gas particles undergo completely elastic collisions with each other and the container walls.

Question 7

A mixture of gases contains O$$_2 at 0.622 $$bar and N$$_2 at 0.517 $$bar at 292 K. What is the total pressure of the mixture?

Accepted Answer

$$P_{	ext{total}} = P_{O_2$} + P_{N_2$} = 0.622 + 0.517 = 1.139\ 	ext{bar}$$

Question 8

Which of the following is the correct form of the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 9

If half the amount of gas in a 20 L container escapes at constant pressure and temperature, what is the new volume?

Accepted Answer

$$V_2$$ = \frac{$$n_2$$}{$$n_1$$} $$V_1$$ = \frac{0.5n_1}{$$n_1$$} 	imes 20 = 10\ 	ext{L}$$

Question 10

Which of the following best describes the relationship between the rate of effusion and molar mass according to Graham's law?

Accepted Answer

$$	ext{Rate} \propto \frac{1}{\sqrt{M}}$$

Question 11

A gas sample at 292 K contains O$$_2 at 0.622 $$bar and N$$_2 at 0.517 $$bar. If the total pressure is 1.139 bar, what is the mole fraction of O$$_2$$?

Accepted Answer

$$x_{O_2$} = \frac{P_{O_2$}}{P_{	ext{total}}} = \frac{0.622}{1.139} = 0.546$$

Question 12

Which of the following conditions causes the greatest deviation from ideal gas behavior?

Accepted Answer

Low temperature and high pressure

Question 13

What is the density of a gas with molar mass $$M at $$pressure $$P$$ and temperature $$T$$ using the ideal gas law?

Accepted Answer

$$d = \frac{MP}{RT}$$

Question 14

A mixture of gases is collected over water at 25°C with a total pressure of 758.2 Torr. If the vapor pressure of water at 25°C is 23.770 Torr, what is the partial pressure of the collected hydrogen gas?

Accepted Answer

$$P_{H_2$} = P_{	ext{total}} - P_{H_2O} = 758.2 - 23.770 = 734.4\ 	ext{Torr}$$

Question 15

Which correction does the van der Waals equation introduce to the ideal gas law?

Accepted Answer

It accounts for intermolecular attractions and the finite volume of gas particles.

Question 16

Which of the following is the correct van der Waals equation for real gases?

Accepted Answer

$$(P + \frac{a n^2$}{V^2$})(V - n b) = nRT$$

Question 17

If the average kinetic energy of a gas particle is given by $$KE = \frac{1}{2} m u^2$, what happens to the average velocity u$ if the molar mass M$ increases at constant temperature?

Accepted Answer

The average velocity $$u$$ decreases.

Question 18

Which of the following best describes diffusion?

Accepted Answer

The process by which a gas spreads through another gas.

Chapter 5: Gases – Properties, Laws, and Molecular Theory

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