This question has Statement-1 and Statement-2. Of the four choices… | JEE Main 2013 (23 Apr, Shift 1)

Q37JEE Main 2013 · 23 APR · SHIFT 1Easy

Degrees of Freedom & Internal Energy

This question has Statement-1 and Statement-2. Of the four choices given after the Statements, choose the one that best describes the two Statements.

Statement 1: The internal energy of a perfect gas is entirely kinetic and depends only on absolute temperature of the gas and not on its pressure or volume.

Statement 2: A perfect gas is heated keeping pressure constant and later at constant volume. For the same amount of heat the temperature of the gas at constant pressure is lower than that at constant volume.

Show answer and solution

Answer: (c)

Statement 1: a perfect gas has no intermolecular forces, so $U$ is only kinetic and depends only on $T$ . True.
Statement 2: at constant $P$ part of the heat does work $P\Delta V$ , so $\Delta T = \frac{Q}{nC_p} < \frac{Q}{nC_v}$ . True.
Statement 2 is about $C_p > C_v$ , not about why $U$ depends only on $T$ , so it does not explain Statement 1.
So the answer is (c).

Report a mistake

Degrees of Freedom & Internal Energy question from JEE Main 2013 (23 Apr, Shift 1)

More questions on Degrees of Freedom & Internal Energy