If enthalpies of formation of `C_(2)H_(4)(g)1` and`H_(2)O(l)` at`25(@)C` and`1`atm pressure be `52,-394`and`-286kJmol^(-1)`respectively ,the enthalpy of combustion of `C_(2)H_(4)(g)`will be

Options

A. `1412KJmol^(-1)`
B. `-1412KJmol^(-1)`
C. `+141.2KJmol^(-1)`
D. `-141.2KJmol^(-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]`
`=-1412KJmol^(-1)`