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. `+1412 kJ 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)rarr2CO_(2)+2H_(2)O`
`DeltaH_("reaction")=[2xxDeltaH_(f)^(@)(CO_(2))+2xxDeltaH_(f)^(@)(H_(2)O)]-DeltaH_(f)^(@)(C_(2)H_(4))+3xxDeltaH_(f)^(@)(O_(2))]`
`=[2(-394)+2(-286)]-[52+0]=-1412 kJ`.