An ideal monoatomic gas initially at 300 K expands adiabatically into vacuum to double its volume. T — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Expansion into vacuum is free expansion, where external pressure $P_{ext} = 0$. Work done is 0. Since it is adiabatic, heat exchange $q = 0$. Therefore, $\Delta U = q + w = 0$. For an ideal gas, internal energy is a function of temperature only, so $\Delta T = 0$. The final temperature remains 300 K.