Computer the heat of reaction at 1000°C for 12H2(g)+12Cl2(g)→HCl(g);ΔH298K∘=92.236kJmol−1Cp∘H2,g=29.0284−0.8355×10−3T+2.0097×10−6T2Cp∘Cl2,g=31.6555+1.0134×10−2T−4.0337×10−6T2Cp∘(HCl,g)=28.1359+1.8078×10−3T+1.5453×10−6T2

ΔH1273K∘=ΔH298K∘+∫298K1273K ΔCpdT Where ΔCp=Cp∘(HCl,g)−12Cp∘H2,g−12Cp∘Cl2,g=28.1359−12×29.0284−12×31.6555+1.8078+12×0.8355−12×10.134×10−3T+1.5453−12×2.0097+12×4.0337×10−6T2Hence, ΔH1273K∘ =+2.5573×10−6×10−6127333−29833Jmol−1 =−92236−2151.0+2176.2+1736.0=−94827Jmol−1 =−94.827kJmol−1