One mole of monoatomic ideal gas at T K is expanded from 1 L to 2 L adiabatically under a constant e — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

For an adiabatic process against a constant external pressure, Δ U = w => n * $C_v$ * (T_final - T_initial) = -P_ext * (V_final - V_initial). For 1 mole of monoatomic gas, $C_v$ = 1.5 * R. So 1 * 1.5 * R * (Tf - T) = -1 * (2 - 1) L-atm = -1 L-atm. In terms of L-atm/K-mol, R = 0.0821. Thus, 1.5 * 0.0821 * (Tf - T) = -1 => Tf - T = -1 / (1.5 * 0.0821) = -2 / (3 * 0.0821) => Tf = T - 2 / (3 * 0.0821).