Q: A manometer is used to measure the pressure of a gas in a vessel. If the height difference of the mercury column is 50 mm and atmospheric pressure is 760 mm Hg, what is the pressure of the gas?

$$P_{\text{gas}} = 760\ \text{mm Hg} + 50\ \text{mm Hg} = 810\ \text{mm Hg}$$

Q: A sample of gas has a mass of 10.0 g, occupies 5.00 L at 2.00 atm and 300 K. What is the molar mass of the gas?

$$M = \frac{mRT}{PV} = \frac{10.0 \times 0.08206 \times 300}{2.00 \times 5.00} = 24.6\ \text{g/mol}$$

Q: A mixture contains 2 moles of O$$_2$$ and 3 moles of N$$_2 at a $$total pressure of 5 atm. What is the partial pressure of N$$_2$$?

$$P_{N_2$} = \frac{3}{5} \times 5 = 3\ \text{atm}$$

Q: If the average kinetic energy of gas molecules is proportional to absolute temperature, which equation expresses this relationship?

$$\text{KE}_{\text{avg}} = \frac{3}{2} R T$$

Question 1

Which of the following statements best describes the physical characteristics of gases compared to liquids and solids?

Accepted Answer

Gases expand to fill their containers and are highly compressible.

Question 2

A manometer is used to measure the pressure of a gas in a vessel. If the height difference of the mercury column is 50 mm and atmospheric pressure is 760 mm Hg, what is the pressure of the gas?

Accepted Answer

$$P_{	ext{gas}} = 760\ 	ext{mm Hg} + 50\ 	ext{mm Hg} = 810\ 	ext{mm Hg}$$

Question 3

Which equation represents Boyle’s Law for a fixed quantity of gas at constant temperature?

Accepted Answer

$$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 4

A balloon filled with helium rises in the atmosphere. Which property of gases explains this behavior?

Accepted Answer

Gases have low density compared to air.

Question 5

At STP, what is the volume occupied by one mole of any ideal gas?

Accepted Answer

$$22.4\ 	ext{L}$$

Question 6

Which of the following is the correct ideal gas equation?

Accepted Answer

$$P V = n R T$$

Question 7

A sample of gas has a mass of 10.0 g, occupies 5.00 L at 2.00 atm and 300 K. What is the molar mass of the gas?

Accepted Answer

$$M = \frac{mRT}{PV} = \frac{10.0 	imes 0.08206 	imes 300}{2.00 	imes 5.00} = 24.6\ 	ext{g/mol}$$

Question 8

Which law states that the total pressure of a mixture of non-reacting gases is the sum of the pressures each gas would exert if it were alone?

Accepted Answer

Dalton’s Law of Partial Pressures

Question 9

A mixture contains 2 moles of O$$_2$$ and 3 moles of N$$_2 at a $$total pressure of 5 atm. What is the partial pressure of N$$_2$$?

Accepted Answer

$$P_{N_2$} = \frac{3}{5} 	imes 5 = 3\ 	ext{atm}$$

Question 10

According to the kinetic-molecular theory, what happens to the pressure of a gas if the temperature increases at constant volume?

Accepted Answer

Pressure increases due to more frequent and forceful collisions.

Question 11

Which equation can be used to calculate the density of a gas using the ideal gas law?

Accepted Answer

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

Question 12

Which of the following gases will effuse fastest through a pinhole at the same temperature?

Accepted Answer

H$$_2$$

Question 13

A real gas deviates from ideal behavior at low temperature and high pressure because:

Accepted Answer

Gas molecules occupy significant volume and experience intermolecular attractions.

Question 14

Which equation is used to correct for nonideal behavior in real gases?

Accepted Answer

van der Waals equation

Question 15

If the average kinetic energy of gas molecules is proportional to absolute temperature, which equation expresses this relationship?

Accepted Answer

$$	ext{KE}_{	ext{avg}} = \frac{3}{2} R T$$

Question 16

A 5.00 L container holds a mixture of 1.00 mol He and 2.00 mol Ne at 300 K. What is the mole fraction of Ne?

Accepted Answer

$$X_{Ne} = \frac{2.00}{1.00 + 2.00} = 0.67$$

Question 17

Which of the following is NOT an assumption of the kinetic-molecular theory?

Accepted Answer

Gas molecules experience significant attractive and repulsive forces.

Question 18

According to Graham’s Law, what is the ratio of the rates of effusion of hydrogen (H$$_2) to $$oxygen (O$$_2$$)?

Accepted Answer

$$\frac{	ext{Rate}_{H_2$}}{	ext{Rate}_{O_2$}} = \sqrt{\frac{M_{O_2$}}{M_{H_2$}}}$$

Question 19

A chemical reaction produces 2.00 moles of CO$$_2$$ gas at STP. What volume will the CO$$_2$$ occupy?

Accepted Answer

$$V = 2.00 	imes 22.4 = 44.8\ 	ext{L}$$

Chapter 10: Gases – Properties, Laws, and Real Behavior

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