Question 1

Which of the following statements best describes the difference between real gases and ideal gases?

Accepted Answer

Real gases have intermolecular forces and finite molecular volume, while ideal gases do not.

Question 2

The van der Waals equation for real gases is given by $$\left(P + \frac{a}{V_m^2$}\right)(V_m - b) = RT. $$What do the parameters $$a$$ and $$b$$ physically represent?

Accepted Answer

$$a$$ accounts for intermolecular attractions, $$b$$ for the finite volume of molecules.

Question 3

At very high pressures and low temperatures, which behavior is most likely observed in real gases?

Accepted Answer

They condense to form liquids.

Question 4

Which equation of state is most accurate for predicting the behavior of gases near their critical point?

Accepted Answer

The van der Waals equation $$\left(P + \frac{a}{V_m^2$}\right)(V_m - b) = RT$$

Question 5

A sample of CO$$_2 is at $$its critical temperature and pressure. According to the phase diagram, what happens if the temperature is increased slightly while keeping the pressure constant?

Accepted Answer

The substance remains a supercritical fluid.

Question 6

Which of the following is the correct form of the Redlich-Kwong equation of state for real gases?

Accepted Answer

$$P = \frac{RT}{V_m - b} - \frac{a}{\sqrt{T}V_m(V_m + b)}$$

Question 7

The Law of Corresponding States suggests that gases at the same reduced temperature and reduced pressure will:

Accepted Answer

Exhibit similar physical properties regardless of their chemical identity.

Question 8

Given the van der Waals equation $$\left(P + \frac{a}{V_m^2$}\right)(V_m - b) = RT$$, which term becomes most significant at low molar volumes?

Accepted Answer

$$\frac{a}{V_m^2$}$$

Question 9

A real gas is found to deviate from ideal behavior at high pressures. Which factor is primarily responsible for this deviation?

Accepted Answer

The finite volume of gas molecules becomes significant.

Question 10

Which of the following best explains why the ideal gas law fails to predict the condensation of gases into liquids?

Accepted Answer

It does not include intermolecular attractions.

Question 11

The compressibility factor $$Z is $$defined as $$Z = \frac{PV_m}{RT}. $$For an ideal gas, what is the value of $$Z$$?

Accepted Answer

$$Z = 1$$

Question 12

A gas sample at 300 K and 10 atm shows a compressibility factor $$Z \u003c 1. $$What does this indicate about the behavior of the gas?

Accepted Answer

Intermolecular attractions dominate.

Question 13

Which of the following is NOT a reason for the deviation of real gases from ideal behavior?

Accepted Answer

High temperature and low pressure.

Question 14

If a real gas is compressed at constant temperature, which of the following is most likely to occur as the molar volume decreases?

Accepted Answer

The pressure increases less than predicted by the ideal gas law due to intermolecular attractions.

Question 15

Which equation is used to estimate the critical temperature $$T_c$$ for a van der Waals gas?

Accepted Answer

$$T_c = \frac{8a}{27Rb}$$

Question 16

A cylinder contains CO$$_2 at 305 K $$and 73 atm. According to the phase diagram, what phase(s) are present?

Accepted Answer

Gas and liquid coexist

Question 17

Which of the following is a limitation of the van der Waals equation when applied to real gases?

Accepted Answer

It is less accurate at very high pressures and very low temperatures.

Question 18

A real gas is observed to have $$Z \u003e 1 at $$high pressure. What does this suggest about the dominant molecular interaction?

Accepted Answer

Intermolecular repulsions dominate.

Question 19

Which of the following best describes the significance of the Law of Corresponding States?

Accepted Answer

It shows that all gases behave identically at the same reduced variables.

Study Notes: Properties of Real Gases

Study Guide - Practice Questions

Study Guide - Flashcards