②求2v H2(g+1/202(g)===H20(g) 反应前后物质的化学计量数（△）=-0.5， ∴.p☑V=0gRT=-0.5×8.314×373=-1.55kJ· mol 1 Qp=2w+∠nRT Qy=2p-∠nRT =-241.9-(-1.55)=-240.35kJ·mol-1 ②求 QV H2 (g)+ 1/2O2 (g) ===== H2O(g) 反应前后物质的化学计量数 ΣυB (Δ n) = - 0.5， ∴ pΔV = ΣυBRT = - 0.5  8.314  373 = - 1.55 kJ · mol – 1 ∵ Qp = Qv + nRT ∴ Qv = Qp – nRT = - 241.9 – (-1.55) = - 240.35 kJ ·mol – 1