Q: A mixture of gases contains nitrogen, oxygen, and argon at partial pressures of 400 mmHg, 300 mmHg, and 100 mmHg, respectively. What is the total pressure of the mixture?

$$400 + 300 + 100 = 800 \ \text{mmHg}$$

Q: Which equation correctly expresses Dalton's Law of Partial Pressures for a mixture of three gases?

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

Q: A 5.0 L cylinder at 30°C contains 112.0 g of helium and 20.0 g of oxygen. What is the total pressure in the cylinder? (Use $$R = 0.0821 \ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K}$$, $$M_{He} = 4.00 \ \text{g/mol}$$, $$M_{O_2$} = 32.0 \ \text{g/mol}$$, $$T = 303 \ \text{K})$$

$$P = \frac{nRT}{V} = \frac{28 + 0.625}{5.0} \times 0.0821 \times 303 = 30.4 \ \text{atm}$$

Q: If the fractional composition of oxygen in a gas mixture is 21% and the total pressure is 760 mmHg, what is the partial pressure of oxygen?

$$P_{O_2$} = 0.21 \times 760 = 159.6 \ \text{mmHg}$$

Q: A gas mixture used for calibration in medical laboratories contains 5.0% CO$$_2$$, 12.0% O$$_2$$, and the rest N$$_2 at a $$total pressure of 1.00 atm. What is the partial pressure of O$$_2$$?

$$P_{O_2$} = 0.12 \times 1.00 = 0.12 \ \text{atm}$$

Q: A scuba tank contains a mixture of helium and oxygen at a total pressure of 200 atm. If the mole fraction of helium is 0.8, what is the partial pressure of helium?

$$P_{He} = 0.8 \times 200 = 160 \ \text{atm}$$

Q: A gas mixture contains 72.0% nitrogen and 28.0% neon at a total pressure of 800 mmHg. What is the partial pressure of neon?

$$P_{Ne} = 0.28 \times 800 = 224 \ \text{mmHg}$$

Q: If the total pressure of a gas mixture is 1.50 atm and the partial pressures of two of the gases are 0.50 atm and 0.75 atm, what is the partial pressure of the third gas?

$$P_3 = 1.50 - 0.50 - 0.75 = 0.25$$ \ \text{atm}$$

Q: A 10.0 L container holds a mixture of gases at 27°C. If the mixture contains 2.0 mol of N$$_2$$ and 3.0 mol of O$$_2$$, what is the total pressure? ($$R = 0.0821 \ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K}$$, $$T = 300 \ \text{K})$$

$$P = \frac{nRT}{V} = \frac{5.0 \times 0.0821 \times 300}{10.0} = 12.3 \ \text{atm}$$

Question 1

A mixture of gases contains nitrogen, oxygen, and argon at partial pressures of 400 mmHg, 300 mmHg, and 100 mmHg, respectively. What is the total pressure of the mixture?

Accepted Answer

$$400 + 300 + 100 = 800 \ 	ext{mmHg}$$

Question 2

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

Accepted Answer

$$P_	ext{total} = P_1$ + P_2$ + P_3$

Question 3

A 5.0 L cylinder at 30°C contains 112.0 g of helium and 20.0 g of oxygen. What is the total pressure in the cylinder? (Use $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$M_{He} = 4.00 \ 	ext{g/mol}$$, $$M_{O_2$} = 32.0 \ 	ext{g/mol}$$, $$T = 303 \ 	ext{K})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{28 + 0.625}{5.0} 	imes 0.0821 	imes 303 = 30.4 \ 	ext{atm}$$

Question 4

If the fractional composition of oxygen in a gas mixture is 21% and the total pressure is 760 mmHg, what is the partial pressure of oxygen?

Accepted Answer

$$P_{O_2$} = 0.21 	imes 760 = 159.6 \ 	ext{mmHg}$$

Question 5

A gas mixture used for calibration in medical laboratories contains 5.0% CO$$_2$$, 12.0% O$$_2$$, and the rest N$$_2 at a $$total pressure of 1.00 atm. What is the partial pressure of O$$_2$$?

Accepted Answer

$$P_{O_2$} = 0.12 	imes 1.00 = 0.12 \ 	ext{atm}$$

Question 6

Which of the following best describes the relationship between the number of moles of a gas and its partial pressure in a mixture, assuming constant volume and temperature?

Accepted Answer

Partial pressure is directly proportional to the number of moles.

Question 7

A scuba tank contains a mixture of helium and oxygen at a total pressure of 200 atm. If the mole fraction of helium is 0.8, what is the partial pressure of helium?

Accepted Answer

$$P_{He} = 0.8 	imes 200 = 160 \ 	ext{atm}$$

Question 8

A gas mixture contains 72.0% nitrogen and 28.0% neon at a total pressure of 800 mmHg. What is the partial pressure of neon?

Accepted Answer

$$P_{Ne} = 0.28 	imes 800 = 224 \ 	ext{mmHg}$$

Question 9

If the total pressure of a gas mixture is 1.50 atm and the partial pressures of two of the gases are 0.50 atm and 0.75 atm, what is the partial pressure of the third gas?

Accepted Answer

$$P_3 = 1.50 - 0.50 - 0.75 = 0.25$$ \ 	ext{atm}$$

Question 10

A 10.0 L container holds a mixture of gases at 27°C. If the mixture contains 2.0 mol of N$$_2$$ and 3.0 mol of O$$_2$$, what is the total pressure? ($$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$T = 300 \ 	ext{K})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{5.0 	imes 0.0821 	imes 300}{10.0} = 12.3 \ 	ext{atm}$$

Question 11

A hospital uses a gas mixture for anesthesia that contains 30% nitrous oxide and 70% oxygen at a total pressure of 2.0 atm. What is the partial pressure of nitrous oxide?

Accepted Answer

$$P_{N_2O} = 0.30 	imes 2.0 = 0.60 \ 	ext{atm}$$

Question 12

A gas mixture in a 2.0 L container at 25°C contains 0.5 mol of CO$$_2$$ and 1.0 mol of N$$_2. $$What is the partial pressure of CO$$_2$$? ($$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$T = 298 \ 	ext{K})$$

Accepted Answer

$$P_{CO_2$} = \frac{0.5 	imes 0.0821 	imes 298}{2.0} = 6.12 \ 	ext{atm}$$

Question 13

A gas mixture contains 3.0 mol of hydrogen and 2.0 mol of neon in a 4.0 L container at 27°C. What is the partial pressure of neon? ($$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$T = 300 \ 	ext{K})$$

Accepted Answer

$$P_{Ne} = \frac{2.0 	imes 0.0821 	imes 300}{4.0} = 12.3 \ 	ext{atm}$$

Question 14

A gas mixture contains 1.0 mol of methane and 4.0 mol of argon. What is the mole fraction of methane?

Accepted Answer

$$X_{CH_4$} = \frac{1.0}{1.0 + 4.0} = 0.20$$

Dalton’s Law of Partial Pressures and Gas Mixtures

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