Q: A scuba diver descends to a depth of 20 meters, where the pressure is approximately 3 atm. If the diver's lungs have a volume of 6.0 L at the surface (1 atm), what will be the volume of the air in the diver's lungs at 20 meters, assuming temperature remains constant and the diver does not exhale?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1 \ \text{atm} \times 6.0 \ \text{L}}{3 \ \text{atm}} = 2.0 \ \text{L}$$

Q: A 5.00 L container holds a gas at 2.00 atm and 300 K. If the temperature is increased to 600 K and the pressure is kept constant, what will be the new volume of the gas?

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 5.00 \ \text{L} \times \frac{600 \ \text{K}}{300 \ \text{K}} = 10.0 \ \text{L}$$

Q: A sample of nitrogen gas has a density of 1.25 g/L at STP. What is the molar mass of nitrogen gas?

$$M = d \times V_m = 1.25 \ \text{g/L} \times 22.4 \ \text{L/mol} = 28.0 \ \text{g/mol}$$

Q: A mixture of gases contains 0.50 mol of O$$_2$$, 0.30 mol of N$$_2$$, and 0.20 mol of CO$$_2 in a 10.0 L $$container at 300 K. What is the total pressure of the mixture?

$$P_{\text{total}} = \frac{n_{\text{total}}RT}{V} = \frac{(0.50+0.30+0.20) \times 0.08206 \times 300}{10.0} = 0.246 \ \text{atm}$$

Q: A 2.00 g sample of an unknown gas occupies 1.50 L at 1.00 atm and 273 K. What is the molar mass of the gas?

$$n = \frac{PV}{RT} = \frac{1.00 \times 1.50}{0.08206 \times 273} = 0.067 \ \text{mol}$$; $$M = \frac{2.00}{0.067} = 29.9 \ \text{g/mol}$$

Q: A gas occupies 10.0 L at 3.00 atm and 27°C. What volume will it occupy at STP?

$$n = \frac{PV}{RT} = \frac{3.00 \times 10.0}{0.08206 \times 300} = 1.22 \ \text{mol}$$; $$V_{\text{STP}} = 1.22 \times 22.4 = 27.3 \ \text{L}$$

Question 1

A scuba diver descends to a depth of 20 meters, where the pressure is approximately 3 atm. If the diver's lungs have a volume of 6.0 L at the surface (1 atm), what will be the volume of the air in the diver's lungs at 20 meters, assuming temperature remains constant and the diver does not exhale?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1 \ 	ext{atm} 	imes 6.0 \ 	ext{L}}{3 \ 	ext{atm}} = 2.0 \ 	ext{L}$$

Question 2

Which of the following best explains why atmospheric pressure decreases with increasing altitude?

Accepted Answer

The number of gas particles per unit volume decreases as altitude increases.

Question 3

A 5.00 L container holds a gas at 2.00 atm and 300 K. If the temperature is increased to 600 K and the pressure is kept constant, what will be the new volume of the gas?

Accepted Answer

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 5.00 \ 	ext{L} 	imes \frac{600 \ 	ext{K}}{300 \ 	ext{K}} = 10.0 \ 	ext{L}$$

Question 4

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

Accepted Answer

The average kinetic energy of gas particles is directly proportional to the absolute temperature.

Question 5

A sample of nitrogen gas has a density of 1.25 g/L at STP. What is the molar mass of nitrogen gas?

Accepted Answer

$$M = d 	imes V_m = 1.25 \ 	ext{g/L} 	imes 22.4 \ 	ext{L/mol} = 28.0 \ 	ext{g/mol}$$

Question 6

A mixture of gases contains 0.50 mol of O$$_2$$, 0.30 mol of N$$_2$$, and 0.20 mol of CO$$_2 in a 10.0 L $$container at 300 K. What is the total pressure of the mixture?

Accepted Answer

$$P_{	ext{total}} = \frac{n_{	ext{total}}RT}{V} = \frac{(0.50+0.30+0.20) 	imes 0.08206 	imes 300}{10.0} = 0.246 \ 	ext{atm}$$

Question 7

A 2.00 g sample of an unknown gas occupies 1.50 L at 1.00 atm and 273 K. What is the molar mass of the gas?

Accepted Answer

$$n = \frac{PV}{RT} = \frac{1.00 	imes 1.50}{0.08206 	imes 273} = 0.067 \ 	ext{mol}$$; $$M = \frac{2.00}{0.067} = 29.9 \ 	ext{g/mol}$$

Question 8

Which of the following best describes the relationship between the pressure and volume of a gas at constant temperature?

Accepted Answer

Pressure is inversely proportional to volume: $$P \propto \frac{1}{V}$$

Question 9

A gas occupies 10.0 L at 3.00 atm and 27°C. What volume will it occupy at STP?

Accepted Answer

$$n = \frac{PV}{RT} = \frac{3.00 	imes 10.0}{0.08206 	imes 300} = 1.22 \ 	ext{mol}$$; $$V_{	ext{STP}} = 1.22 	imes 22.4 = 27.3 \ 	ext{L}$$

Question 10

Which of the following is a correct statement about the molar volume of gases at STP?

Accepted Answer

All ideal gases occupy 22.4 L per mole at STP, regardless of their identity.

Question 11

A 3.50 g sample of zinc reacts completely with hydrochloric acid to produce hydrogen gas. What volume of hydrogen gas is produced at STP? (Zn = 65.38 g/mol, H$$_2 = 2.02 g/$$mol, reaction: Zn + 2HCl → ZnCl$$_2 + H$_2)$$

Accepted Answer

$$n_{	ext{Zn}} = \frac{3.50}{65.38} = 0.0535 \ 	ext{mol}$$; \$$n_{	ext{H}_2$$} = 0.0535 \ 	ext{mol}$$; V = 0.0535$$ 	imes 22.4 = 1.20 \ 	ext{L}$

Question 12

Which of the following best explains why helium balloons rise in air?

Accepted Answer

Helium is less dense than air, so the buoyant force pushes the balloon upward.

Question 13

A mixture of gases contains 2.0 mol of O$$_2$$ and 3.0 mol of N$$_2. If $$the total pressure is 5.0 atm, what is the partial pressure of O$$_2$$?

Accepted Answer

$$P_{O_2$} = X_{O_2$} 	imes P_{	ext{total}} = \frac{2.0}{2.0+3.0} 	imes 5.0 = 2.0 \ 	ext{atm}$$

Question 14

Which of the following is NOT an assumption of the kinetic molecular theory for ideal gases?

Accepted Answer

Gas particles are strongly attracted to each other.

Question 15

A 0.17 mol sample of neon is in a 8.7 L container at 25°C. What is the partial pressure of neon?

Accepted Answer

$$P = \frac{nRT}{V} = \frac{0.17 	imes 0.08206 	imes 298}{8.7} = 0.48 \ 	ext{atm}$$

Question 16

Which of the following best describes the effect of increasing temperature on the average speed of gas molecules?

Accepted Answer

The average speed of gas molecules increases as temperature increases.

Question 17

Which of the following gases will diffuse the fastest under identical conditions?

Accepted Answer

Hydrogen ($$H_2)$$

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