CH4(g)+2O2(g)→CO2(g)+2H2O(l)∆H=‌ ? ‌ To get this equation reverse equation (i) write equation (ii) as it is, multiply equation (iii) by 2 and add all these equations, we will get ∆H ∴∆H=+74.8+‌(−393.5)+(−286.2×2) ‌=−891.1‌kJ