The enthalpy of formation for `C_(2)H_(4)(g)`, `CO_(2)(g)` and `H_(2)O(l)` at `25^(@)C` and `1` atm. Pressure be `52`, `-394` and `-286 kJ mol^(-1)` respectively. The enthalpy of combustion of `C_(2)H_(4)(g)` will be

Options

A. `+1412kJ mol^(-1)`
B. `- 1412 kJ mol^(-1)`
C. `+141.2 kJ mol^(-1)`
D. `- 141.2 kJ mol^(-1)`

Answer

B

Explanation

`C_(2)H_(4) + 3O_(2) rarr 2CO_(2) + 2H_(2)O`
`Delta H_("reaction")= [2 xx Delta H_(f)^(@) (CO_(2)) + 2 xx Delta H_(f)^(@) (H_(2)O)]- [Delta H_(f)^(@) (C_(2)H_(4))+3 xx Delta H_(f)^(@) (O_(2))]`
`=[2(-394)+2 (-286)]- [52+0]= -1412kJ`