`E_(Fe^(3+)//Fe^(+2))^(0)=+0.77V,E_(Fe^(+3)//Fe)^(0)=0.036V` . What is `E_(Fe//Fe^(+2))^(0)` and is `Fe^(+2)` stable to disproportionation in aqueous solution under standard conditions

Options

A. `+0.44 V,` yes
B. `-0.44V`, No
C. `+0.44 V`, No
D. `-0.44 V`, yes

Answer

1

Explanation

`Fe^(3+)+e^(-)rarr Fe^(2+)" "(1)E_(1)^(@)=0.77V" "DeltaG_(1)^(@)=-1xxFxx0.77`
`Fe^(3+)+3e^(-)rarrFe" "(2)E_(2)^(@)=-0.036V" "DeltaG_(2)^(@)=3xxFxx0.036`
`FerarrFe^(2+)+2e^(-)" "(3)E_(3)=DeltaG_(3)^(@)=-2xxFxxE_(3)^(@)`
`(1)-(2)=3`
`DeltaG_(1)^(@)-DeltaG_(2)^(@)=DeltaG_(3)^(@)`
`rArr-Fxx0.77-3F-0.036=-2xFxxE_(3)^(@)" "rArr(0.77xx0.108)=2xxE_(3)^(@)" "rArrE_(3)^(@)~=0.44V Ans.`
Disproportionation reaction.
`3Fe^(2+)rarrFe+2Fe^(3+)" "(4)`
`Fe^(2+)+2e^(-) rarr Fe`
`E^(@)=-0.44V" "DeltaG^(@)=-2xxFxx(-0.44)(5)`
`Fe^(2+)rarr Fe^(3+)+e^(-)`
`E^(@)=-0.77V" "DeltaG^(@)=-1xxFxx(0.77)=+ve" "(6)`
`:'DeltaG_(4)^(@)=-2xxFxx(0.44)+2(-1xxFxx(-0.77))=+ve`
`:' DeltaG_(4)^(@) gt 0," "rArr` Reaction is not spontaneous.
Hence, `Fe^(2+)` is stable to disproportiionation.