1.

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

Answer»

1.968 V
2.0968V
1.0968V
0.0968V

Solution :The balanced equation for pentane-oxygen cell reaction will be
`C_(5)H_(12)+8O_(2)to5CO_(2)+6H_(2)O,n=32`
`Delta_(r)G^(@)=[5xxDelta_(F)G^(@)(CO_(2))+6Delta_(f)G^(@)(H_(2)O)]-[Delta_(f)G^(@)(C_(5)H_(12))+8Delta_(f)G^(@)(O_(2))]`
`=[5(-394.5)+6(-237.2)]-[(-8.2)+0]`
`=-1972-1423.2+8.2=-3387" KJ "mol^(-1)`
`Delta_(f)G^(@)=-nFE_(ceLL)^(@)`
`therefore-3387000=-32xx96500xxE_(cell)^(@)`
or `E_(cell)^(@)=1.0968V`


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