Standard molar heat of formation of ethane, `CO_(2)` and water are `-21.1 , -94.1 and -68.3` kcal respectively. Calculate the molar heat of combustion of ethane.

Explanation

`2C("graphite,s")+3H_(2)(g) to C_(2)H_(6)(g), Delta H^(0)= - 21.1 ` kcal ..[1]
`C("graphite,s")+O_(2)(g) to CO_(2)(g), Delta H^(0)=- 94.1` kcal .. [2]
`H_(2)(g)+(1)/(2)O_(2)(g) to H_(2)O (l), Delta H^(0)= - 68.3 " kJ mol"^(-1)` .. [3]
`2 xx "equation "[2]+3xx "equation"[3] - "equation"[1]`, we have `C_(2)H_(6)(g)+(7)/(2)O_(2)(g) to 2CO_(2)(g)+3H_(2)O(l)`
`DeltaH^(0)= [2(-94.1)+3(-68.3)- (-21.1)` kcal= - 372 kcal