Question 1

A mixture of gases in a sealed container has a total pressure of 800 mm Hg. If the mole fraction of nitrogen ($$N_2) is 0.25$$, what is the partial pressure of $$N_2 in $$the mixture?

Accepted Answer

$$200 mm Hg$$

Question 2

According to Dalton's Law of Partial Pressures, which of the following equations correctly expresses the total pressure of a mixture of gases?

Accepted Answer

$$P_{total} = P_1$ + P_2$ + P_3$

Question 3

A gas mixture contains 0.015 mole fraction $$CO_2$$, 0.18 mole fraction $$O_2$$, and 0.805 mole fraction Ar. If the total pressure is 745 mm Hg, what is the partial pressure of $$O_2$$?

Accepted Answer

$$P_{O_2$} = 134.1 mm Hg$$

Question 4

If the $$CO_2 is $$removed from the mixture in the previous question, what is the new mole fraction of $$O_2$$?

Accepted Answer

$$X_{O_2$} = 0.1827$$

Question 5

Which of the following is a correct statement of the kinetic molecular theory of gases?

Accepted Answer

The average kinetic energy of gas molecules is proportional to the temperature in Kelvin.

Question 6

Which postulate of the kinetic molecular theory explains why gases are easily compressible?

Accepted Answer

The volume of gas molecules is much less than the volume of the container.

Question 7

According to the Maxwell-Boltzmann distribution, what happens to the distribution of molecular speeds as temperature increases?

Accepted Answer

The distribution becomes broader and shifts to higher speeds.

Question 8

For two different gases at the same temperature, which gas will have a lower average speed?

Accepted Answer

The gas with the higher molar mass.

Question 9

Which of the following best describes the process of effusion?

Accepted Answer

The escape of gas molecules through a small opening under pressure.

Question 10

According to Graham's Law, the rate of effusion of a gas is:

Accepted Answer

Inversely proportional to the square root of its molar mass.

Question 11

An unknown gas effuses at a rate that is 0.468 times that of $$O_2 at $$the same temperature. What is the molar mass of the unknown gas? ($$M_{O_2$} = 32 g/$$mol)

Accepted Answer

$$M_{unknown} = 146 g/$$mol

Question 12

Which of the following statements about mean free path is correct?

Accepted Answer

It is the average distance a gas molecule travels between collisions.

Question 13

A hospital stores a mixture of oxygen and nitrogen in a tank at a total pressure of 10 atm. If the mole fraction of oxygen is 0.3, what is the partial pressure of nitrogen?

Accepted Answer

$$P_{N_2$} = 7$$ atm

Question 14

Which of the following is NOT a postulate of the kinetic molecular theory?

Accepted Answer

Gas molecules attract each other strongly.

Question 15

Which real-world scenario best illustrates Graham's Law of Effusion?

Accepted Answer

Helium balloons deflating faster than air-filled balloons.

Question 16

If the total number of moles in a gas mixture is 5.0 mol and the mixture contains 1.0 mol of $$CO_2$$, what is the mole fraction of $$CO_2$$?

Accepted Answer

$$0.2$$

Question 17

Which of the following best describes diffusion?

Accepted Answer

The gradual mixing of molecules of one gas with those of another.

Question 18

A sample of hydrogen gas and a sample of oxygen gas are at the same temperature. Which statement is true about their average kinetic energies?

Accepted Answer

Both have the same average kinetic energy.

Question 19

Which equation correctly relates the partial pressure of a gas to its mole fraction and the total pressure?

Accepted Answer

$$P_A = X_A 	imes P_{total}$$

Question 20

Which of the following would increase the mean free path of gas molecules in a container?

Accepted Answer

Decreasing the number of gas molecules.

Lecture 21

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