Question 1

Which of the following statements best describes the difference between effusion and diffusion?

Accepted Answer

Effusion refers to the movement of gas molecules through a small hole, while diffusion refers to the mixing of gases.

Question 2

According to Graham’s Law, if gas A has a molar mass of 16 g/mol and gas B has a molar mass of 64 g/mol, what is the ratio of their rates of effusion ($\frac{	ext{Rate}_A}{	ext{Rate}_B}$)?

Accepted Answer

$2$

Question 3

A sample of an unknown gas effuses at 0.342 times the rate of helium ($M_{He} = 4.00\ g\cdot mol^{-1}$). What is the molar mass of the unknown gas?

Accepted Answer

$34.2\ g\cdot mol^{-1}$

Question 4

Which of the following gases will have the lowest rate of diffusion at the same temperature?

Accepted Answer

$Rn$ ($M = 222\ g\cdot mol^{-1}$)

Question 5

Which condition is most likely to cause a real gas to deviate from ideal behavior?

Accepted Answer

High pressure and low temperature

Question 6

Which assumption of the ideal gas law is violated at very high pressures?

Accepted Answer

Gas molecules have negligible volume compared to the container.

Question 7

What is the effect of intermolecular forces on the pressure exerted by a real gas compared to an ideal gas?

Accepted Answer

The pressure exerted by a real gas is lower than that predicted by the ideal gas law.

Question 8

Which equation best represents the ideal gas law?

Accepted Answer

$PV = nRT$

Question 9

A real gas occupies a volume larger than predicted by the ideal gas law at high pressure. Which factor in the van der Waals equation accounts for this?

Accepted Answer

The $b$ term, which corrects for molecular volume.

Question 10

Given the van der Waals equation $\left(P + a \left(\frac{n}{V}\right)^2\right)(V - nb) = nRT$, what does the $a$ parameter correct for?

Accepted Answer

Intermolecular attractive forces

Question 11

A sample of gas at 300 K and 1 atm occupies 22.4 L. If the pressure is increased to 10 atm at constant temperature, what will happen to the mean free path of the gas molecules?

Accepted Answer

It will decrease.

Question 12

Which of the following is NOT an assumption of the kinetic molecular theory for ideal gases?

Accepted Answer

Gas molecules exert attractive and repulsive forces on each other.

Question 13

If the temperature of a gas is doubled at constant volume, what happens to the pressure according to the ideal gas law?

Accepted Answer

It doubles.

Question 14

A mixture of gases contains $N_2$ and $O_2$. Which gas will diffuse faster and why?

Accepted Answer

$N_2$ will diffuse faster because it has a lower molar mass.

Question 15

Which of the following best explains why real gases deviate from ideal behavior at low temperatures?

Accepted Answer

Intermolecular attractions become significant, reducing the pressure exerted by the gas.

Question 16

A 10.0 mol sample of a real gas ($a = 6.00\ 	ext{bar}\cdot L^2\cdot mol^{-2}$, $b = 0.0500\ L\cdot mol^{-1}$) fills a 1.00 L container at 500 bar. What is the temperature of the gas sample according to the van der Waals equation?

Accepted Answer

$662\ K$

Question 17

Which of the following is a consequence of non-elastic collisions in real gases?

Accepted Answer

The pressure exerted by the gas is lower than predicted by the ideal gas law.

Question 18

Which of the following equations gives the root mean square speed ($u_{rms}$) of a gas molecule?

Accepted Answer

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

Question 19

If a gas sample has $PV/RT < 1$, what does this indicate about the behavior of the gas?

Accepted Answer

Intermolecular attractions are significant.

Chapter 5.6: Gases – Properties, Laws, and Real Gas Behavior

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