Question

During free expansion of an ideal gas under adiabatic condition, the internal energy of the gas

• A. Decreases
• B. Initially decreases and then increases
• C. Increases
• D. Remains constant

Hint:

In adiabatic expansion of an ideal gas, there is no heat exchange, so the internal energy changes only due to work done by or on the gas.

Answer 1

The Correct Option is D

Step 1: Understanding free expansion of an ideal gas.
In the free expansion of an ideal gas, the gas expands into a vacuum without doing any work. Since the process is adiabatic (no heat exchange with the surroundings), the internal energy of the gas decreases. This is because the gas expands and does not gain any energy from external sources.

Step 2: Analyzing the options.
(A) Decreases: Correct. The internal energy decreases as the gas expands adiabatically, following the first law of thermodynamics.
(B) Initially decreases and then increases: Incorrect. The internal energy continuously decreases during the free expansion.
(C) Increases: Incorrect. The internal energy does not increase in free expansion.
(D) Remains constant: Incorrect. The internal energy decreases during the expansion, so it does not remain constant.

Step 3: Conclusion.
The correct answer is (A) Decreases because the gas loses internal energy as it expands without heat exchange.