The difference between `Delta H` and `Delta E` (on a molar basis) for the combustion of n-octane `(l)` at `25^(@)C` would be:

Options

A. `13.6 kJ`
B. `-1.14 kJ`
C. `-11.15 kJ`
D. `+11.15 kJ`

Answer

C

Explanation

`C_(8)H_(18)(l)+(25)/(2)O_(2)(g)rarr8CO_(2)(g)+9H_(2)O(l)`
`Delta n_(g)=8-(25)/(2)=(16-25)/(2)= -(9)/(2)= -4.5`
`Delta H-Delta E= Delta_(g)RT= -(4.5xx8.314xx298)/(1000)= -11.15 kJ`