Given `C_(s)+O_(2(g))toCO_(2(g)),DeltaH=-94.2K cal`
`H_(2(g))+½O_(2(g))toH_(2)O_((g)),Delta=-68.3K cal`
`CH_(4(g))+2O_(2(g))+2H=-210.8K cal`
what will be heat of gormation of ` CH_(4)` in (Kcal) ?

Options

A. `+49.9`
B. `-20.0`
C. `+47.8`
D. `-47.3`

Answer

B

Explanation

`(1)+2xx(2)-(3)`
`DeltaH_(F)(CH_(4))=Delta_(1)+2DeltaH_(2)-DeltaH_(3)`
`=-94.2+2xx(-68.3)-(-210.8)`
`=-20KCal`