Find the heat of formation of ethyl alcohol for following data
`C(s) +O_(2)(g) rarr CO_(2)(g) DeltaH =- 94 kcal`
`H_(2)(g) +1//2O_(2)(g) rarr H_(2)O(l), DeltaH =- 68 kcal`
`C_(2)H_(5)OH(l)+3O_(2)(g) rarr 2CO_(2)(g) +3H_(2)O(l) DeltaH =- 327 kcal`

Explanation

On the basis of definition of formation, the following hermochemical equation is written for which `Delta H_(f)` is to be calculated : `2C(s)+3H_(2)(g)+(1)/(2)O_(2)(g)rarr C_(2)H_(5)OH(l),Delta H_(f) = ?`
Given data may be written as follows because thermochemical equation act as algebraic equations
`{:((i),2C(s)+2O_(2)(g)rarr2CO_(2)(g),,Delta H=-188 kcal),((ii),3H_(2)(g)+(3)/(2)O_(2)(g)rarr 3H_(2)O(l)",",,Delta H=-204 kcal),((iii),2CO_(2)(g)+3H_(2)O(l)rarr C_(2)H_(5)OH(l)+3O_(2)(g),,Delta H=+327 kcal),(,"On addition "2C(s)+3H_(2)(g)+(1)/(2)O_(2)(g)rarr C_(2)H_(5)OH(l)",",,Delta H_(f)=-65 kcal//mol.):}`