2 moles of an ideal monoatomic gas undergoes reversible expansion from (4 L, 400 K) to 8 L such that — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

T1 = 400 K, V1 = 4 L, V2 = 8 L. TV^2 = constant => T1 * V1^2 = T2 * V2^2 => 400 * 16 = T2 * 64 => T2 = 100 K. The change in temperature is dT = T2 - T1 = 100 - 400 = -300 K. For a monoatomic ideal gas, $C_p$ = 2.5 R. For n = 2 moles, Δ H = n * $C_p$ * dT = 2 * 2.5 R * (-300) = -1500 R.