Question 1

A basketball is inflated with air, causing it to expand from a flat shape to a spherical one. Which gas law best explains why the basketball expands as air is added, assuming temperature is constant?

Accepted Answer

Boyle's Law: $$P_1V_1 = P_2V_2$$

Question 2

Which of the following best describes the origin of gas pressure in a closed container?

Accepted Answer

Gas molecules colliding with the container walls.

Question 3

If the number of gas molecules in a sealed jar is doubled while the volume and temperature remain constant, what happens to the pressure?

Accepted Answer

The pressure doubles.

Question 4

A J-tube is used to compress a gas by adding mercury. What happens to the pressure and volume of the gas as more mercury is added, assuming temperature is constant?

Accepted Answer

Pressure increases, volume decreases.

Question 5

A sample of gas is compressed from 1.0 L to 0.5 L at constant temperature. According to Boyle’s Law, what happens to the pressure?

Accepted Answer

It doubles.

Question 6

A balloon is placed in ice water and then in boiling water. What happens to the volume of the balloon and why?

Accepted Answer

The volume increases because the temperature increases, raising the kinetic energy of the gas molecules.

Question 7

According to Avogadro’s Law, what is the relationship between the volume of a gas and the number of moles at constant temperature and pressure?

Accepted Answer

Volume is directly proportional to the number of moles: $$V \propto n$$

Question 8

Which of the following statements is true about the molar volume of gases at STP?

Accepted Answer

One mole of any ideal gas occupies 22.4 L at STP.

Question 9

Which gas will have the lowest density at STP: Ne, $$O_2$$, $$F_2$$, or $$Cl_2$$?

Accepted Answer

Neon (Ne)

Question 10

A 12.5-L scuba 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? ($$R = 0.08206\ \mathrm{L\cdot atm/(mol\cdot K)}$$; He: 4.00 g/mol, $$O_2$$: 32.00 g/mol)

Accepted Answer

$$P = 4.72$$ atm

Question 11

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

Accepted Answer

Gas particles are in constant, random motion and collisions are perfectly elastic.

Question 12

Which equation gives the root mean square velocity ($$u_{rms}) of a $$gas particle?

Accepted Answer

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

Question 13

According to Graham’s Law, how does the rate of effusion of hydrogen gas ($$H_2) $$compare to that of oxygen gas ($$O_2) at $$the same temperature?

Accepted Answer

Hydrogen effuses about four times faster than oxygen.

Question 14

Which of the following is a reason real gases deviate from ideal behavior at high pressures?

Accepted Answer

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

Question 15

Which modification does the van der Waals equation introduce to account for intermolecular attractions?

Accepted Answer

It subtracts a term $$a\left(\frac{n}{V}\$$right)^2$$ from the pressure.

Question 16

A reaction occurs in a sealed, rigid container. As the reaction proceeds, the total number of gas molecules decreases. What happens to the total pressure?

Accepted Answer

The total pressure decreases.

Question 17

Which of the following best explains why a helium balloon rises in air?

Accepted Answer

Helium has a lower density than air.

Question 18

If the mean free path of a gas molecule decreases, what does this indicate about the pressure?

Accepted Answer

The pressure has increased.

Question 19

A mixture of gases contains 2.0 mol $$N_2$$, 1.0 mol $$O_2$$, and 1.0 mol $$CO_2 in a 10.0 L $$container at 300 K. What is the mole fraction of $$O_2$$?

Accepted Answer

$$\chi_{O_2$} = 0.25$$

Chapter 6: Gases – Properties, Laws, and Real Gas Behavior

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