Q: A gas sample is contained in a 2.0 L vessel at 1.0 atm and 300 K. If the pressure is doubled and the temperature is increased to 600 K, what will be the new volume of the gas (assuming the amount of gas is constant)?

$V_2 = \frac{P_1 V_1 T_2}{T_1 P_2} = \frac{(1.0\ \text{atm})(2.0\ \text{L})(600\ \text{K})}{(300\ \text{K})(2.0\ \text{atm})} = 2.0\ \text{L}$

Q: A 248-mL gas sample has a mass of 0.433 g at a pressure of 745 mmHg and a temperature of 28 °C. What is the molar mass of the gas? (Use $R = 0.0821\ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K}$)

$M = \frac{mRT}{PV} = \frac{0.433 \times 0.0821 \times 301}{0.248 \times 0.980} = 57.7\ \text{g/mol}$

Question 1

Which of the following statements best explains why gases are highly compressible compared to liquids and solids?

Accepted Answer

Gas molecules are much farther apart than those in liquids and solids, so there is more empty space that can be reduced.

Question 2

Which variable must be measured in Kelvin when using the ideal gas law?

Accepted Answer

Temperature

Question 3

A gas sample is contained in a 2.0 L vessel at 1.0 atm and 300 K. If the pressure is doubled and the temperature is increased to 600 K, what will be the new volume of the gas (assuming the amount of gas is constant)?

Accepted Answer

$V_2 = \frac{P_1 V_1 T_2}{T_1 P_2} = \frac{(1.0\ 	ext{atm})(2.0\ 	ext{L})(600\ 	ext{K})}{(300\ 	ext{K})(2.0\ 	ext{atm})} = 2.0\ 	ext{L}$

Question 4

According to the kinetic-molecular theory, which of the following is NOT an assumption made about ideal gases?

Accepted Answer

Gas molecules experience significant attractive and repulsive forces.

Question 5

Which of the following correctly expresses Boyle’s Law?

Accepted Answer

$P_1 V_1 = P_2 V_2$

Question 6

A 0.250 mol sample of gas occupies 6.15 L at 298 K and 1.00 atm. If the amount of gas is doubled at constant temperature and pressure, what will be the new volume?

Accepted Answer

12.3 L

Question 7

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

Accepted Answer

$PV = nRT$

Question 8

A 10.0 L cylinder contains 0.448 mol of nitrogen gas at 315 K. What is the pressure inside the cylinder? (Use $R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$)

Accepted Answer

$P = \frac{nRT}{V} = \frac{(0.448)(0.0821)(315)}{10.0} = 1.16\ 	ext{atm}$

Question 9

Which of the following best describes the relationship between the average kinetic energy of gas molecules and temperature?

Accepted Answer

The average kinetic energy is directly proportional to the absolute temperature (in Kelvin).

Question 10

A weather balloon is filled to a volume of 28.5 L at 748 mmHg and 28.0 °C. It rises to an altitude where the pressure is 385 mmHg and the temperature is -15.0 °C. What is the new volume of the balloon? (Use the combined gas law.)

Accepted Answer

$V_2 = \frac{P_1 V_1 T_2}{T_1 P_2} = \frac{(748)(28.5)(258)}{(301)(385)} = 47.7\ 	ext{L}$

Question 11

Which of the following is NOT a correct unit conversion for pressure?

Accepted Answer

1 atm = 22.4 L

Question 12

A 248-mL gas sample has a mass of 0.433 g at a pressure of 745 mmHg and a temperature of 28 °C. What is the molar mass of the gas? (Use $R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$)

Accepted Answer

$M = \frac{mRT}{PV} = \frac{0.433 	imes 0.0821 	imes 301}{0.248 	imes 0.980} = 57.7\ 	ext{g/mol}$

Question 13

Dalton’s Law of Partial Pressures states that:

Accepted Answer

The total pressure of a mixture of gases equals the sum of the partial pressures of each individual gas.

Question 14

A gas mixture contains 2.0 mol of O$_2$ and 3.0 mol of N$_2$ in a 10.0 L container at 300 K. What is the total pressure of the mixture? (Use $R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$)

Accepted Answer

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

Question 15

Which of the following best explains why real gases deviate from ideal behavior at high pressures and low temperatures?

Accepted Answer

Attractive forces and the finite volume of gas molecules become significant.

Question 16

Which equation is used to correct for non-ideal gas behavior?

Accepted Answer

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

Question 17

A sample of gas has a density of 1.31 g/L at 1.00 atm and 273 K. What is the molar mass of the gas? (Use $R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$)

Accepted Answer

$M = \frac{dRT}{P} = \frac{1.31 	imes 0.0821 	imes 273}{1.00} = 29.4\ 	ext{g/mol}$

Chapter 10: Gases – Properties, Laws, and Calculations

Study Guide - Practice Questions

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