Question

Calculate the standard enthalpy of combustion of methane given that standard enthalpy of combustion of carbon and hydrogen are _393.5 and _283.83kj respectively standard enthalpy of formation of methane is _75.16

Answer 1

CH4(g)+O2(g)→CO2(g)+2H2O(l)+Δrxn

Now it is a fact that....

ΔH∘rxn=ΣΔH∘f(products)−ΣΔH∘f(reactants)

And we have been given the appropriate data...

ΔH∘rxn={(−393.5−2×286)−(−74.85)}⋅kJ⋅mol−1

=−890.7⋅kJ⋅mol−1