Question 1

Which property distinguishes gases from liquids and solids, as illustrated by their ability to occupy the entire volume of their container?

Accepted Answer

Gases are highly compressible and expand to fill their container.

Question 2

A mercury barometer measures atmospheric pressure by balancing the pressure exerted by the atmosphere with the pressure exerted by a column of mercury. If the height of the mercury column is 760 mm, what is the atmospheric pressure in pascals?

Accepted Answer

$$1.01325 	imes 10^5$ Pa

Question 3

Refer to the graphs showing the relationship between volume and pressure for a gas. Which law is demonstrated by the inverse relationship between volume and pressure?

Accepted Answer

Boyle's Law

Question 4

A gas sample is compressed from low pressure to high pressure, as shown in the diagram. What happens to the volume of the gas?

Accepted Answer

The volume decreases.

Question 5

At STP (0°C and 1 atm), 22.4 L of He, N2, and CH4 each contain $$6.02 	imes 10$$^{23}$$ molecules. Which law explains why the number of molecules is the same for each gas?

Accepted Answer

Avogadro's Law

Question 6

A 5.0 g sample of CH4 occupies what volume at 25°C and 1 atm? (Molar mass of CH4 = 16.0 g/mol, $$R = 0.08206 L$$·atm/mol·K)

Accepted Answer

$$7.7 L$$

Question 7

A mixture contains 0.77 mol He, 0.33 mol Ne, and 0.11 mol Ar in a 10.5 L vessel at 25°C. What is the partial pressure of Ne? ($$R = 0.08206 L$$·atm/mol·K)

Accepted Answer

$$0.78$$ atm$

Question 8

Which equation relates the density ($$\delta) of a $$gas to its molar mass ($$M$$), pressure ($$P$$), and temperature ($$T$$)?

Accepted Answer

$$\delta = \frac{PM}{RT}$$

Question 9

According to Dalton’s Law of Partial Pressures, what is the total pressure of a gas mixture?

Accepted Answer

The sum of the partial pressures of each gas.

Question 10

A mixture of gases contains 0.75 mol N2, 0.30 mol O2, and 0.15 mol CO2. If the total pressure is 2.15 atm, what is the partial pressure of O2?

Accepted Answer

$$0.645$$ atm

Question 11

According to the kinetic-molecular theory, what causes the pressure exerted by a gas in a container?

Accepted Answer

Collisions of gas molecules with the container walls.

Question 12

The root-mean-square speed ($$u_{rms}) of a $$gas molecule is given by which equation?

Accepted Answer

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

Question 13

Which gas will effuse fastest through a pinhole: H2, CO, HF, Xe, or Br2?

Accepted Answer

H2

Question 14

A helium balloon deflates faster than a nitrogen balloon. Which principle explains this observation?

Accepted Answer

Helium has a lower molar mass and effuses faster.

Question 15

If the mean free path of air molecules at sea level is about 60 nm, what happens to the mean free path as pressure increases?

Accepted Answer

It decreases.

Question 16

A gas sample is heated from 0°C to 100°C. What happens to the fraction of molecules moving at speeds greater than 500 m/s?

Accepted Answer

It increases.

Question 17

A 2.5 L sample of gas at 25°C is heated to 50°C at constant pressure. What is the new volume?

Accepted Answer

$$2.7 L$$

Question 18

Which equation is used to calculate the molar mass ($$M) of a $$gas from its density ($$\delta$$), temperature ($$T$$), and pressure ($$P$$)?

Accepted Answer

$$M = \frac{\delta RT}{P}$$

Question 19

A gas effuses at a rate that is 0.355 times the rate of O2. What is the molar mass of the unknown gas? (Molar mass of O2 = 32 g/mol)

Accepted Answer

$$254 g/$$mol

Question 20

Which of the following statements about gases is NOT correct?

Accepted Answer

Gas molecules interact strongly with each other.

Chapter 10: Gases – Properties, Laws, and Molecular Theory

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