Standard electrode potentials for Fe electrodes are given as
`Fe^(2+)+2e^(-)toFe, E^@=-0.44` V
`Fe^(3+)+e^(-)toFe^(2+),E^@=+0.77` V
`Fe^(2+),Fe^(3+)` and Fe blocks are kept together then

Options

A. `[Fe^(3+)]` decreases
B. `[Fe^(3+)]` increases
C. `[Fe^(2+)]//[Fe^(3+)]` remains unchanged
D. `[Fe^(2+)]` decreases.

Answer

A

Explanation

`Fe^(2+)//Fe` acts as anode because its standard reduction potential is low i.e., oxidation occurs at this electrode and `Fe^(2+)//Fe` acts as cathode because its standard reduction potential is high i.e., reduction occurs at this electrode.
`therefore` `FetoFe^(2+)+2e^(-)(Anode)`
and `(Fe^(3+)+e^(-)toFe^(2+)xx2(Cathode))/(Fe+2Fe^(3+)to3Fe^(2+))` Thus, if `Fe^(2+), Fe^(3+)` and Fe blocks are kept together, `Fe^(3+)` get reduced to `Fe^(2+)` i.e., concentration of `Fe^(3+)` decreases.