Question 1

According to the Kinetic Molecular Theory (KMT), which of the following statements is TRUE about the behavior of ideal gases?

Accepted Answer

The volume of individual gas molecules is negligible compared to the total volume occupied by the gas.

Question 2

Which equation correctly expresses the relationship between the root-mean-square speed ($$u_{rms}) of a $$gas and its molar mass ($$M) at $$temperature $$T$$?

Accepted Answer

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

Question 3

A sample of helium gas and a sample of oxygen gas are at the same temperature. Which statement is correct regarding their average kinetic energies and molecular speeds?

Accepted Answer

Both gases have the same average kinetic energy, but helium atoms move faster.

Question 4

Which of the following best explains why lighter gas molecules, such as hydrogen, diffuse faster than heavier molecules like oxygen?

Accepted Answer

Lighter molecules have a greater root-mean-square speed at the same temperature.

Question 5

A rigid container holds 1 mole of $$\mathrm{N_2$}$$ gas at 300 K and 1 mole of $$\mathrm{O_2$}$$ gas at 300 K. Which statement is true about their average kinetic energies?

Accepted Answer

Both gases have the same average kinetic energy.

Question 6

A gas sample at 25°C is found to have a root-mean-square speed ($$u_{rms}) of 482 m/s. If $$the molar mass of the gas is doubled and the temperature remains constant, what happens to $$u_{rms}$$?

Accepted Answer

$$u_{rms}$$ decreases by a factor of $$\sqrt{2}.$$

Question 7

Which of the following correctly describes Graham’s Law of Effusion?

Accepted Answer

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

Question 8

A mixture of hydrogen and argon gases is kept at the same temperature. Which gas will have a greater mean free path, assuming both are at the same pressure?

Accepted Answer

Both gases have the same mean free path under these conditions.

Question 9

If the temperature of a gas is doubled (in Kelvin) while keeping the volume and number of moles constant, what happens to the pressure according to the ideal gas law?

Accepted Answer

The pressure doubles.

Question 10

Which of the following scenarios would result in the highest total kinetic energy for the gas sample?

Accepted Answer

100 molecules of $$\mathrm{N_2$} at 250 K$$

Question 11

Which of the following best describes the effect of decreasing pressure on the mean free path of gas molecules?

Accepted Answer

The mean free path increases because there are fewer collisions.

Question 12

A gas sample is allowed to effuse through a small hole. If the rate of effusion of an unknown gas is 0.342 times that of oxygen ($$\mathrm{O_2$}$$), what is the molar mass of the unknown gas? (Molar mass of $$\mathrm{O_2$} = 32 g/$$mol)

Accepted Answer

274 g/mol

Question 13

Which of the following equations represents the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 14

Which postulate of the Kinetic Molecular Theory explains why gas pressure increases with temperature?

Accepted Answer

The average kinetic energy of gas particles is proportional to the temperature in kelvins.

Question 15

A 1.00 mol sample of $$\mathrm{O_2$}$$ gas is at 25°C. Calculate its root-mean-square speed ($$u_{rms}). (R = 8.314 J/$$mol·K, $$M = 32.0 g/$$mol)

Accepted Answer

$$u_{rms} = 482\ \mathrm{m/s}$$

Question 16

Which of the following best describes diffusion?

Accepted Answer

The process by which gas molecules move from an area of high concentration to low concentration.

Question 17

If the temperature of a gas is increased from 200 K to 400 K, what happens to the average kinetic energy of its molecules?

Accepted Answer

It doubles.

Question 18

Which of the following is NOT an assumption of the Kinetic Molecular Theory for ideal gases?

Accepted Answer

Gas particles have significant volume compared to the container.

Question 19

A gas sample in a hospital oxygen tank is stored at high pressure. According to KMT, what effect does this have on the mean free path of the oxygen molecules?

Accepted Answer

The mean free path decreases because there are more frequent collisions.

Question 20

Which of the following best explains why the velocity distribution of gas molecules broadens as temperature increases?

Accepted Answer

At higher temperatures, the range of molecular speeds increases.

Chapter 5.5: Gases – Kinetic Molecular Theory, Gas Laws, and Molecular Motion

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