Q: A mixture of helium, neon, and argon has a total pressure of 662 mmHg at 298 K. If the partial pressure of helium is 341 mmHg and the partial pressure of neon is 112 mmHg, what is the partial pressure of argon in the mixture?

$$P_{Ar} = 662\ \text{mmHg} - (341\ \text{mmHg} + 112\ \text{mmHg}) = 209\ \text{mmHg}$$

Q: A student collects hydrogen gas over water at 25°C. The total pressure is 755 mmHg. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of hydrogen gas?

$$P_{H_2$} = 755\ \text{mmHg} - 23.8\ \text{mmHg} = 731.2\ \text{mmHg}$$

Q: If 1.00 L of a gas mixture at 298 K contains 0.135 mol of argon, what is the partial pressure of argon? (Use $$R = 0.0821\ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K})$$

$$P_{Ar} = \frac{nRT}{V} = \frac{0.135 \times 0.0821 \times 298}{1.00} = 3.30\ \text{atm}$$

Q: A mixture of gases contains 0.60 mol N$$_2$$ and 1.35 mol O$$_2 in a 1.25 L $$container at 298 K. What is the total pressure of the mixture? ($$R = 0.0821\ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K})$$

$$P_{total} = \frac{(0.60 + 1.35) \times 0.0821 \times 298}{1.25} = 38.0\ \text{atm}$$

Q: A sample of oxygen gas is collected over water at 20°C. The total pressure is 755.2 mmHg and the vapor pressure of water at 20°C is 17.5 mmHg. What is the partial pressure of oxygen?

$$P_{O_2$} = 755.2\ \text{mmHg} - 17.5\ \text{mmHg} = 737.7\ \text{mmHg}$$

Question 1

A mixture of helium, neon, and argon has a total pressure of 662 mmHg at 298 K. If the partial pressure of helium is 341 mmHg and the partial pressure of neon is 112 mmHg, what is the partial pressure of argon in the mixture?

Accepted Answer

$$P_{Ar} = 662\ 	ext{mmHg} - (341\ 	ext{mmHg} + 112\ 	ext{mmHg}) = 209\ 	ext{mmHg}$$

Question 2

Which equation correctly expresses Dalton’s Law of Partial Pressures for a mixture of gases?

Accepted Answer

$$P_{total} = P_1$ + P_2$ + P_3$ + \ldots$$

Question 3

A student collects hydrogen gas over water at 25°C. The total pressure is 755 mmHg. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of hydrogen gas?

Accepted Answer

$$P_{H_2$} = 755\ 	ext{mmHg} - 23.8\ 	ext{mmHg} = 731.2\ 	ext{mmHg}$$

Question 4

If 1.00 L of a gas mixture at 298 K contains 0.135 mol of argon, what is the partial pressure of argon? (Use $$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P_{Ar} = \frac{nRT}{V} = \frac{0.135 	imes 0.0821 	imes 298}{1.00} = 3.30\ 	ext{atm}$$

Question 5

A mixture contains 2.42 g of N$$_2$$ and 4.32 g of O$$_2. $$Calculate the mole fraction of N$$_2 in $$the mixture.

Accepted Answer

$$\chi_{N_2$} = \frac{n_{N_2$}}{n_{N_2$} + n_{O_2$}} = \frac{0.086}{0.086 + 0.135} = 0.389$$

Question 6

Which of the following best describes the process of collecting a gas over water?

Accepted Answer

The total pressure measured is the sum of the partial pressure of the collected gas and the vapor pressure of water.

Question 7

A mixture of gases contains 0.60 mol N$$_2$$ and 1.35 mol O$$_2 in a 1.25 L $$container at 298 K. What is the total pressure of the mixture? ($$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P_{total} = \frac{(0.60 + 1.35) 	imes 0.0821 	imes 298}{1.25} = 38.0\ 	ext{atm}$$

Question 8

Which of the following is the correct formula for calculating the mole fraction of a component in a mixture?

Accepted Answer

$$\chi_i = \frac{n_i}{n_{total}}$$

Question 9

A gas mixture contains 0.135 mol of argon and 0.112 mol of neon in a 1.00 L container at 298 K. What is the mole fraction of neon?

Accepted Answer

$$\chi_{Ne} = \frac{0.112}{0.135 + 0.112} = 0.453$$

Question 10

A sample of oxygen gas is collected over water at 20°C. The total pressure is 755.2 mmHg and the vapor pressure of water at 20°C is 17.5 mmHg. What is the partial pressure of oxygen?

Accepted Answer

$$P_{O_2$} = 755.2\ 	ext{mmHg} - 17.5\ 	ext{mmHg} = 737.7\ 	ext{mmHg}$$

Question 11

A 1.02 L sample of oxygen gas is collected over water at 20°C and a total pressure of 755.2 mmHg. What is the mass of oxygen gas collected? (Vapor pressure of water at 20°C is 17.5 mmHg, $$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$T = 293\ 	ext{K}$$, $$M_{O_2$} = 32.00\ 	ext{g/mol})$$

Accepted Answer

$$m_{O_2$} = 1.32\ 	ext{g}$$

Question 12

Which of the following statements about partial pressures is TRUE?

Accepted Answer

The partial pressure of a gas in a mixture is proportional to its mole fraction.

Question 13

A mixture of gases contains 0.60 mol N$$_2$$ and 1.35 mol O$$_2 in a 1.25 L $$container at 298 K. What is the partial pressure of N$$_2$$? ($$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P_{N_2$} = \frac{0.60 	imes 0.0821 	imes 298}{1.25} = 11.7\ 	ext{atm}$$

Question 14

Which of the following is a correct application of the ideal gas law to find the number of moles of a gas?

Accepted Answer

$$n = \frac{PV}{RT}$$

Question 15

A mixture of gases contains 0.086 mol N$$_2$$ and 0.135 mol O$$_2. If $$the total pressure is 1.00 atm, what is the partial pressure of O$$_2$$?

Accepted Answer

$$P_{O_2$} = \chi_{O_2$} 	imes P_{total} = \frac{0.135}{0.086 + 0.135} 	imes 1.00 = 0.611\ 	ext{atm}$$

Question 16

A gas mixture contains 0.60 mol N$$_2$$ and 1.35 mol O$$_2 in a 1.25 L $$container at 298 K. What is the mole fraction of O$$_2$$?

Accepted Answer

$$\chi_{O_2$} = \frac{1.35}{0.60 + 1.35} = 0.692$$

Question 17

Which of the following is the correct relationship for the partial pressure of a component in a mixture using mole fraction?

Accepted Answer

$$P_i = \chi_i 	imes P_{total}$$

Question 18

A student collects 1.02 L of hydrogen gas over water at 20°C and a total pressure of 755.2 mmHg. The vapor pressure of water at 20°C is 17.5 mmHg. What is the partial pressure of hydrogen gas?

Accepted Answer

$$P_{H_2$} = 755.2\ 	ext{mmHg} - 17.5\ 	ext{mmHg} = 737.7\ 	ext{mmHg}$$

Gas Laws: Total Pressure, Partial Pressures, and Gas Collection Over Water

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