The molar heats of combustion of `C_(2)H_(2)(g)`, C (graphite), and `H_(2)` are `-310.62`kcal, `-94.05` kcal and `-68.32` kcal respectively. Calculate the standard heat of formation of `C_(2)H_(2)(g)`.

Explanation

`{:(C_(2)H_(2)(g) + 2.5 O_(2)(g) to 2CO_(2) + H_(2)O, - 310.62 kcal" "….(a)),(C_("graphite") + O_(2)(g) to CO_(2)(g) , -94.05 kcal " "…...(b)),(H_(2)(g) + 1//2O_(2)(g) to H_(2)O(l),-68.32 kcal" "….(c )):}/ul(2C("graphite")+H_(2)(g) to C_(2)H_(2)(g), DeltaH = 2a+ c - b)`
`Delta H = -2 xx 94 .05 - 68.32 + 310.62 = 54.2 kcal`.