Read the Assertion and Reason below and choose the correct option. — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The temperature of an ideal gas does not *always* decrease in an adiabatic expansion; in an adiabatic free expansion against a vacuum, $W = 0$, resulting in $\Delta U = 0$ and constant temperature. Thus, Statement I is incorrect. Statement II is correct according to the first law of thermodynamics ($q = 0$, so $\Delta U = q + w = w$).