Q: A sample of hydrogen gas occupies 3.50 L at 0.750 atm. If the pressure is increased to 1.50 atm at constant temperature, what is the new volume?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.750 \times 3.50}{1.50} = 1.75\ \mathrm{L}$$

Q: A 0.896 L sample of helium gas is heated from 0°C to a final temperature at constant pressure. What is the final temperature in Kelvin?

$$T_2$$ = \frac{$$V_2$$ $$T_1$$}{$$V_1$$} = \frac{0.896 \times 273}{0.678} = 361\ \mathrm{K}$$

Q: If helium ($$M = 4.00\ \mathrm{g/mol}) $$and oxygen ($$M = 32.00\ \mathrm{g/mol}) $$are allowed to effuse through a small hole, what is the ratio of their effusion rates ($$\text{rate}_{He}/\text{rate}_{O_2$}$$)?

$$\text{rate}_{He}/\text{rate}_{O_2$} = \sqrt{\frac{32.00}{4.00}} = 2.83$$

Question 1

Which of the following best explains why breathing is possible according to the gas laws?

Accepted Answer

Muscles change the volume of the chest cavity, altering the pressure inside the lungs and allowing air to flow in or out to balance the pressure.

Question 2

A sample of hydrogen gas occupies 3.50 L at 0.750 atm. If the pressure is increased to 1.50 atm at constant temperature, what is the new volume?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.750 	imes 3.50}{1.50} = 1.75\ \mathrm{L}$$

Question 3

Which equation correctly relates pressure, force, and area for a gas?

Accepted Answer

$$P = \frac{F}{A}$$

Question 4

A 0.896 L sample of helium gas is heated from 0°C to a final temperature at constant pressure. What is the final temperature in Kelvin?

Accepted Answer

$$T_2$$ = \frac{$$V_2$$ $$T_1$$}{$$V_1$$} = \frac{0.896 	imes 273}{0.678} = 361\ \mathrm{K}$$

Question 5

Which statement about the molar volume of an ideal gas at standard temperature and pressure (STP) is correct?

Accepted Answer

The molar volume of any ideal gas at STP is $$22.7\ \mathrm{L/mol}.$$

Question 6

A mixture of gases contains $$O_2 at$$ $$0.622$$ bar and $$N_2 at$$ $$0.517$$ bar at $$292\ \mathrm{K}. $$What is the total pressure of the mixture?

Accepted Answer

$$P_{total} = 0.622 + 0.517 = 1.139\ \mathrm{bar}$$

Question 7

Which of the following best describes the kinetic molecular theory of gases?

Accepted Answer

Gas particles are negligibly small, move randomly, and undergo completely elastic collisions.

Question 8

According to kinetic molecular theory, what happens to the average kinetic energy of gas particles when the temperature increases?

Accepted Answer

It increases.

Question 9

Which equation gives the root-mean-square speed ($$u_{rms}) of a $$gas molecule?

Accepted Answer

$$u_{rms} = \sqrt{\frac{3RT}{M}}$$

Question 10

If helium ($$M = 4.00\ \mathrm{g/mol}) $$and oxygen ($$M = 32.00\ \mathrm{g/mol}) $$are allowed to effuse through a small hole, what is the ratio of their effusion rates ($$	ext{rate}_{He}/	ext{rate}_{O_2$}$$)?

Accepted Answer

$$	ext{rate}_{He}/	ext{rate}_{O_2$} = \sqrt{\frac{32.00}{4.00}} = 2.83$$

Question 11

Which condition causes the greatest deviation from ideal gas behavior?

Accepted Answer

Low temperature and high pressure

Question 12

What correction does the van der Waals equation introduce to the ideal gas law?

Accepted Answer

It accounts for the volume of gas particles and intermolecular attractions.

Question 13

A 22.0 g sample of $$CO_2$$ occupies 15.3 L. If an additional 15.0 g $$CO_2 is $$added at constant temperature and pressure, what is the new volume?

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \frac{$$n_2$$}{$$n_1$$} = 15.3 	imes \frac{0.841}{0.500} = 25.7\ \mathrm{L}$$

Question 14

Which formula is used to calculate the density of a gas using the ideal gas law?

Accepted Answer

$$d = \frac{MP}{RT}$$

Question 15

A gas is collected over water at $$25^\circC $$with a total pressure of $$758.2$$ Torr. The vapor pressure of water at $$25^\circC is$$ $$23.770$$ Torr. What is the partial pressure of the hydrogen gas collected?

Accepted Answer

$$P_{H_2$} = 758.2 - 23.770 = 734.4\ \mathrm{Torr}$$

Question 16

Which of the following is NOT a standard unit of pressure?

Accepted Answer

joule (J)

Question 17

If half the gas sample escapes from a 20 L container at constant pressure and temperature, what is the new volume?

Accepted Answer

$$V_2 = 0.5$$ 	imes 20 = 10\ \mathrm{L}$$

Question 18

Which law states that the volume of a gas is directly proportional to its temperature at constant pressure?

Accepted Answer

Charles's Law

Question 19

In a chemical reaction, 2 mol $$H_2$$ reacts with 1 mol $$O_2 to $$produce water. If you start with 1.32 mol $$H_2$$, what mass of water is produced? ($$M_{H_2O} = 18.02\ \mathrm{g/mol})$$

Accepted Answer

$$1.32\ \mathrm{mol} 	imes 18.02\ \mathrm{g/mol} = 23.8\ \mathrm{g}$$

Chapter 5: Gases – Properties, Laws, and Molecular Theory

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