Q: Which of the following statements about the root mean square speed ($$u_{\text{rms}}) of $$gas molecules is correct?

$$u_{\text{rms}}$$ increases as the temperature increases.

Q: Which of the following is a correct statement about the relationship between the rate of effusion and molar mass for two gases, A and B?

$$\frac{\text{rate}_A}{\text{rate}_B} = \sqrt{\frac{M_B}{M_A}}$$

Question 1

A weather system moves over a city and the barometer reads 755 mmHg. What is this pressure in atmospheres (atm)?

Accepted Answer

$$0.993\ 	ext{atm}$$

Question 2

A 2.00 L sample of gas at 25°C and 1.00 atm is compressed to 1.00 L and simultaneously heated to 50°C. What is the final pressure of the gas? (Assume ideal behavior.)

Accepted Answer

$$2.18\ 	ext{atm}$$

Question 3

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

Accepted Answer

The average kinetic energy of gas molecules depends only on the temperature in Kelvin.

Question 4

A sample of hydrogen gas is collected over water at 298 K. The total pressure is 1007 mbar, and the vapor pressure of water at this temperature is 23.8 mbar. What is the partial pressure of hydrogen gas?

Accepted Answer

$$983.2\ 	ext{mbar}$$

Question 5

A 5.00 L diving tank contains 24.2 g of He and 4.32 g of O$$_2 at 298 K. $$What is the total pressure in the tank? (Use $$R = 0.0821\ 	ext{L atm mol}^{-1}	ext{K}^{-1}.)$$

Accepted Answer

$$10.1\ 	ext{atm}$$

Question 6

Which of the following gases will have the highest root mean square speed ($$u_{	ext{rms}}) at 25$$°C?

Accepted Answer

Hydrogen ($$\mathrm{H}_2)$$

Question 7

A gas sample has a mass of 0.311 g, a volume of 0.225 L, a temperature of 55°C, and a pressure of 886 torr. What is the molar mass of the gas? (Use $$R = 0.0821\ 	ext{L atm mol}^{-1}	ext{K}^{-1}.)$$

Accepted Answer

$$32.0\ 	ext{g mol}^{-1}$$

Question 8

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

Accepted Answer

The volume of the gas particles becomes significant compared to the container volume.

Question 9

A 0.500 L sample of $$\mathrm{H}_2$$ reacts with excess $$\mathrm{O}_2 to $$form water vapor according to $$2\mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2\mathrm{H}_2\mathrm{O}(g). $$What mass of water vapor is produced? (Assume all gases are measured at the same temperature and pressure.)

Accepted Answer

$$0.45\ 	ext{g}$$

Question 10

Which of the following statements about diffusion and effusion is correct?

Accepted Answer

The rate of effusion is inversely proportional to the square root of the molar mass.

Question 11

A gas is collected over water at 25°C. The total pressure is 760 torr, and the vapor pressure of water at this temperature is 24 torr. What is the pressure of the dry gas?

Accepted Answer

$$736\ 	ext{torr}$$

Question 12

Which of the following best describes the effect of intermolecular forces on the pressure of a real gas compared to an ideal gas at low temperatures?

Accepted Answer

The pressure of the real gas is lower than predicted by the ideal gas law.

Question 13

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

Accepted Answer

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

Question 14

A gas sample at STP occupies 22.4 L. If the sample contains 2.00 moles of gas, what is the volume occupied?

Accepted Answer

$$44.8\ 	ext{L}$$

Question 15

Which of the following best explains why the pressure of a gas increases when its volume decreases at constant temperature?

Accepted Answer

Gas molecules collide with the walls more frequently.

Question 16

A mixture contains 2.0 mol of $$\mathrm{N}_2$$ and 1.0 mol of $$\mathrm{O}_2 in a 10.0 L $$container at 300 K. What is the mole fraction of $$\mathrm{O}_2$$?

Accepted Answer

$$0.33$$

Question 17

Which of the following statements about the root mean square speed ($$u_{	ext{rms}}) of $$gas molecules is correct?

Accepted Answer

$$u_{	ext{rms}}$$ increases as the temperature increases.

Question 18

Which of the following is a correct statement about the relationship between the rate of effusion and molar mass for two gases, A and B?

Accepted Answer

$$\frac{	ext{rate}_A}{	ext{rate}_B} = \sqrt{\frac{M_B}{M_A}}$$

Question 19

A gas sample is compressed at constant temperature from 4.00 L to 2.00 L. If the initial pressure was 1.00 atm, what is the final pressure?

Accepted Answer

$$2.00\ 	ext{atm}$$

Chapter 5: Gases – Properties, Laws, and Applications

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