Standard free energies of formation ( in kJ/mol) at 298 K are `-237.2, -394.4` and `-8.2` for `H_(2)O(l), CO_(2)(g)` and pentane (g), respectively . The value of `E_("cell")^(@)` for the pentane-oxygen fuel cell is :

Options

A. 2.0968 V
B. 1.0968 V
C. 0.0968 V
D. 1.968 V

Answer

B

Explanation

`C_(5)H_(12)+8O_(2) rarr 5 CO_(2)+6H_(2)O`
`DeltaG^(@)=5Delta_(f)G^(@)(CO_(2))+6Delta_(f)G^(@)(H_(2)O)-Delta_(f)G^(@)(C_(5)H_(12)-8Delta_(f)G^(@)(O_(2))`
`=5(-394.4)+6(-237.2)-(-8.2)-8xx0`
`= -1972-1423.2+8.2-0`
`= -3387 "kJ mol"^(-1)`
`DeltaG^(@)= -nFE^(@)`
or `E^(@)= -(DeltaG^(@))/(nF)` where `n=32`
`:.E^(@)= -(-3387xx10^(3))/(32xx96500)= 1.0968V`.