How much energy is released when 6 mole of octane is burnt in air ? Given `DeltaH_(f)^(@)` for `CO_(2)(g),H_(2)O(g)` and `C_(8)H_(18)(l)` respectively are `-490,-240` and `+160KJ//mol`

Options

A. `-6.2 KJ`
B. `-37.4 KJ`
C. `-35.5 KJ`
D. `-20.0 KJ.`

Answer

B

Explanation

`C+o_(2)toCO_(2),DeltaH_(f)^(@)=(-490 KJ)/(mol)xx8`
`H_(2)+(2)/(2)O_(2)to,DeltaH_(f)^(@)=(-240 KJ)/(mol)xx9`
`8C+18HtoC_(8)H_(18),DeltaH_(f)^(@)=+160 KJ//mol`
`8C+8O_(2)+9H_(2)-8c-18H`
`to 8CO_(2)+9H_(2)O-C_(8)H_(18)`
`DeltaH_(f)^(@)=-3920-2160-160`
`C_(8)H_(18)(25)/(2)O_(2)to8CO_(2)+9H_(2)O,DeltaH^(@)` ,`=6240 KJ//mol`
`DeltaH^(@)` for 6 moles of octane `=6240x6=37440 KJ//mol`.