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Standard free energies of formation (I k...

Standard free energies of formation (I `kJ //`mol ) at `298 K` are ` -237 .2 , - 394 .4` and `- 8.2 ` for `H_2 O(1), CO_2 (g)` and pentange (g) , respectively . The value of `E_(cell)^@` for the pentane-oxygen fuel cell is .

A

`1.968V`

B

`2.0968V`

C

1.0968V

D

0.0968V

Text Solution

Verified by Experts

The correct Answer is:
C
The balanced equation for the pentane oxygen cell reaction will be
`C_(5)H_(12)+8O_(2)rarr5CO_(2)+6H_(2)O,n=32`
`(because 16O+32e^(-)rarr16O^(2-))`
`DeltaG=5xxDelta_(f)G^(@)(CO_(2))+6 xxDelta _(f)G^(@)(H_(2)O)`
`-Delta_(f)G^(@)(C_(5)H_(12))+8xxDelta_(f)G^(@)(O_(2))`
`= 5xx(-394.4)+6(-237.2)-(-8.2)-0`
`=-1972-1423.2+8.2`
`=-3387 kJ "mol"^(-1)`
`DeltaG_(f)=-nFE_("cell")^(@)`
`therefore -3387000=-32xx96500xxE_("cell")^(@)`
or `E_("cell")^(@)=1.0968V`
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