Ethylene on combustion gives carbon dioxide and water. Its heat of combustion is `1410.0 kJ mol^(-1)`. If the heat of formation of `CO_(2)` and `H_(2)O` are `393.3 kJ` and `286.2 kJ`, respectively. Calculate the heat of formation of ethylene.

Answer

`+51.0 kJ mol^(-1)`

Explanation

Given `:`
(i) `C_(2)H_(4)(g) +(5)/(2) O_(2)(g) rarr 2CO_(2)(g) + 2H_(2)O(l), DeltaH = - 1410.0 kJ mol^(-1)`
(ii) `C(s) + O_(2)(g) rarr CO_(2)(g), DeltaH = - 393.3kJ mol^(-1)`
(iii) `H_(2)(g) + (1)/(2) O_(2)(g) rarr H_(2)O(l), DeltaH = - 286.2kJ mol^(-1)`
Aim `: 2 C(s) + 2H_(2)(g) rarr C_(2)H_(4)(g) DeltaH = ?`
` 2 xx ` Eqn. (ii) `+ 2 xx `Eqn.(iii) - Eqn. (i) gives the required result.