Physical Chemistry Questions and Answers – Ideal Gases

This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Ideal Gases”.

1. The Internal energy of a real gas is a function of pressure as well as of temperature.
a) False
b) True

Explanation: Pressure dependence results from forces between the molecules. If such forces did not exist, no energy would be required to alter the average intermolecular distance.

2. What is the relation between CP and CV for an ideal gas?
a) CP = CV + R
b) CV = R
c) CP = R
d) CP + R = 0

Explanation: CP = CV + R is the relation between CP and CV for an ideal gas. This equation does not imply that CP and CV are themselves constant for an ideal gas, but only that they vary with temperature in such a way that their difference is equal to R.

3. What is the equation of an Isothermal process?
a) Q = -W = RT ln V2/V1 = -RT ln P2/P1
b) Q = ΔH = ∫ CV dT
c) ΔH = ∫ CV dT
d) Q = ΔU = ∫ CV dT

Explanation: ΔU = ΔH = 0
And Q = RT ln V2/V1 = -RT ln P2/P1
W = -RT ln V2/V1 = RT ln P2/P1
Note that Q = -W. Therefore, Q = -W = RT ln V2/V1 = -RT ln P2/P1
Proved.

4. What is the equation of Isobaric process?
a) Q = -W = RT ln V2/V1 = -RT ln P2/P1
b) T2/T1 = (V1/V2)
c) CP + R = 0
d) Q = ΔH = ∫ CP dT

Explanation: ΔU = ∫ CV dT
And ΔH = ∫ CP dT
W = -R (T2 – T1) and Q = ∫ CP dT
Q = ΔH = ∫ CP dT
Proved.

5. What is partial molar property?
a) Pressure that species exert
b) Maintenance of temperature below that of surroundings
c) A process for the continuous conversion of heat into work
d) Equal to corresponding mole property as a pure species

Explanation: A partial molar property (other than volume) of a constituent species in an ideal – gas mixture is equal to the corresponding molar property of the species as a pure ideal gas at the mixture temperature but at a pressure equal to its partial pressure in the mixture.

6. What is the volume of one mole of an ideal gas?
a) 22.710947
b) 33. 87584
c) 44. 97272
d) 55. 08487

Explanation: The volume of one mole of an ideal gas is 22.710947(13) L at STP as defined by IUPAC since 1982.

7. At higher temperature and lower pressure gases behave as an ideal gas.
a) True
b) False

Explanation: Potential energy due to the intermolecular forces become less significant. The size of the molecules also becomes less significant in comparison of empty space between them.

8. The expression for density is __________
a) PM/RT
b) PM = RT
c) 1/RT
d) PM = 0

Explanation: PM/RT is an expression for density. At constant temperature and pressure, the density of the gas is directly proportional to the molar mass of the gas.

9. What is the volume of one mole of gas at ideal conditions?
a) 42.989 dm3
b) 34.671 dm3
c) 22.414 dm3
d) 55.911 dm3

Explanation: The molar volume is the volume occupied by an ideal gas at STP. The molar volume of a gas at ideal conditions is 22.414 dm3 at 0℃ and 24.465 dm3 at 25℃.

10. 1 m3 is equal to?
a) 50 dm3
b) 500 dm3
c) 10 dm3
d) 100 dm3

Explanation: Meter is the unit of length in International System of Units. The SI unit of meter is m. 1 m3 is equal to 100 dm3.

Sanfoundry Global Education & Learning Series – Physical Chemistry.

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