The following reaction are given :
`CH_(4(g))+2O_(2(g))toCO_(2(g))+2H_(2)O(g),DeltaH=-x`
`C_((s))+O_(2(g))toCO_(2(g)),2H_(2(g)),DeltaH=-y`
`H_(2(g))+(1)/(2)O_(2(g))toH_(2)O_((g)),2H_(2(g)),DeltaH=-z`
calculate the heat of formation of `CH_(4)`?

Options

A. x+y+z
B. y+2z-x
C. x-y-2z
D. none of the above

Answer

C

Explanation

`C(s)+2H_(2)(g)toCH_(4)(g),DeltaH_(f)(CH_(4))
DeltaH_(f)(CH_(4))=(2)+2xx(3),-(1)`
`=-y+2(-2)-(-x)`
`rArrx-y-2z`