Question

`DeltaG^(c-)` or the reaction is `,`
`4Al+3O_(2)+6H_(2)O+4overset(c-)(O)H rarr 4 Al(OH)_(4)^(c-)`
`E^(c-)._(cell)=2.73V`
`Delta_(f)G^(c-)._((overset(c)(O)H))=-157k J mol^(-1)`
`Delta_(f)G^(c-)._((overset(c-)(O)H))=-237k J mol^(-1)`

A. `-3.16xx10^(3)kJ mol^(-1)`
B. `-0.79xx10^(3)kJmol^(-1)`
C. `-0.263xx10^(3)k J mol^(-1)`
D. `+0.263xx10^(3)k J mol^(-1)`

Answer 1

Correct Answer - a
`Delta_(r)G^(c-)._(cell)=-n_(cell)FE^(c-)._(cell)=-12xx96500xx2.73`
`=-3.16xx10^(3)k J mol^(-1)`
For `n_(cell)` write the half cell reaction as `:`
Cathode `: 2H_(2)O(l)+O_(2)(g)+4e^(-) rarr 4 overset(c-)(O)H(aq)`
Anode `:Al(s)+4overset(c-)(O)H(aq)rarr Al(OH)_(4)^(c-)(aq)+3e^(-)`