1.

What is the electrode potential for following reaction ? E_(Fe^(+3)|Fe)^(o)=-0.036V,E_(Fe^(2+)|Fe)^(o)=-0.439V Fe^(3+)+e^(-) to Fe^(2+).

Answer»

`-0.072V`
`0.385` V
0.770 V
`-0.270V`

Solution :(i) `Fe^(3+)+3E^(-) to Fe,`
`E_(1)^(o)=-0.036V,DeltaG_(1)^(@)=-3xxFxx(-0.036)`
(II) `Fe^(2+)+2e^(-) to Fe,`
`E_(2)^(@)=-0.439V,DeltaG_(2)^(@)=-2xxFxx(-0.439)`
Required REACTION :
`Fe^(3+)+e^(-) to Fe^(2+)` REDUCTION, `DeltaG_(3)^(@)=-1xxFxxE_(3)^(@)`
SUBTRACT (ii) from (i),
`DeltaG_(3)^(@)=DeltaG_(1)^(@)-DeltaG_(2)^(@)`
`(-1)xxFxxE_(3)^(@)=[-3xxFxx(-0.036)]-[(-2xxFxx-0.439)]`
`therefore -E_(3)^(@)=(0.108-0.878)`
`therefore E_(3)^(@)=(-0.108+0.878)`
`therefore E_(3)^(@)=0.77V`.


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