physics : class11 Kinetic Energy Contribution : Internal Energy : Thermodynamics MCQ Questions and Answers
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Kinetic Energy Contribution
MCQ questions and answers.
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MCQ Questions
1. What is the average translational kinetic energy of one molecule of an ideal gas at absolute temperature T?
A.
kT
B.
3kT
C.
3kT/2
D.
kT/2
Correct Answer:
3kT/2
Explanation:
For an ideal gas molecule, the average translational kinetic energy is directly proportional to absolute temperature and is given by 3kT/2.
2. The kinetic energy contribution to the internal energy of an ideal gas mainly depends on its:
A.
Temperature
B.
Colour
C.
Container shape
D.
Position on Earth
Correct Answer:
Temperature
Explanation:
The average kinetic energy of gas molecules depends on the absolute temperature, so the kinetic contribution to internal energy changes with temperature.
3. If the absolute temperature of an ideal gas is doubled, its average molecular translational kinetic energy becomes:
A.
Half
B.
Unchanged
C.
Four times
D.
Twice
Correct Answer:
Twice
Explanation:
Average translational kinetic energy is directly proportional to absolute temperature. Therefore, doubling the temperature doubles the kinetic energy.
4. At the same temperature, which gas molecules have the same average translational kinetic energy?
A.
Only molecules with the same mass
B.
Molecules of all ideal gases
C.
Only molecules moving at the same speed
D.
Only molecules in the same container
Correct Answer:
Molecules of all ideal gases
Explanation:
The average translational kinetic energy of an ideal gas molecule is 3kT/2, which depends only on temperature and not on the type or mass of the molecule.
5. The average translational kinetic energy of one mole of an ideal gas at temperature T is:
A.
RT/2
B.
RT
C.
3RT/2
D.
3RT
Correct Answer:
3RT/2
Explanation:
Multiplying the energy 3kT/2 per molecule by Avogadro's number gives 3RT/2 per mole.
6. When the temperature of an ideal gas increases, the average speed of its molecules generally:
A.
Decreases
B.
Increases
C.
Becomes zero
D.
Remains exactly the same
Correct Answer:
Increases
Explanation:
An increase in temperature increases the average kinetic energy of the molecules, so their average speed increases.
7. For an ideal gas, the kinetic contribution to internal energy is zero at the theoretical temperature of:
A.
0 degrees Celsius
B.
100 degrees Celsius
C.
Absolute zero
D.
Room temperature
Correct Answer:
Absolute zero
Explanation:
According to the idealized model, molecular translational kinetic energy becomes zero at absolute zero temperature.
8. If the number of molecules in an ideal gas is doubled while its temperature remains constant, the total translational kinetic energy becomes:
A.
Half
B.
Unchanged
C.
Twice
D.
Four times
Correct Answer:
Twice
Explanation:
Each molecule has the same average kinetic energy at constant temperature. Doubling the number of molecules therefore doubles the total kinetic energy.
9. Which expression represents the total translational kinetic energy of N molecules of an ideal gas at temperature T?
A.
NkT/2
B.
3NkT/2
C.
3Nk/T
D.
NkT
Correct Answer:
3NkT/2
Explanation:
Each molecule has an average translational kinetic energy of 3kT/2. For N molecules, the total is 3NkT/2.
10. Two ideal gases are at the same temperature. A molecule of the heavier gas has, on average, the same:
A.
Speed as a molecule of the lighter gas
B.
Momentum as a molecule of the lighter gas
C.
Translational kinetic energy as a molecule of the lighter gas
D.
Mass as a molecule of the lighter gas
Correct Answer:
Translational kinetic energy as a molecule of the lighter gas
Explanation:
At the same temperature, the average translational kinetic energy is 3kT/2 for molecules of any ideal gas, regardless of their mass.
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