The following electrochemical cell has been set up `:`
`Pt(l)|Fe^(3+),Fe(a=1)|Ce^(4+),Ce^(3+)(a=1)|Pt(2)`
`E^(c-)._(((Fe^(3+),Fe^(2+)))=0.77V`
and
`E^(c-)._(((Ce^(4+),Ce^(3+)))=1.61V`
If an ammeter is connected between two platinum electrodes, predict the direction of the flow of current. Will the current increase or decreases with time ?

Answer

Flow of current from cathode to anode and the current will decrease with time.

Explanation

For electrochemical cell
`Pt_((1))|Fe^(3+),Fe^(2+)(a=1)|Ce^(4+),Ce^(3+)(a=1)|Pt_((2))`
`E^(c-)._((Fe^(3+)|Fe^(2+)))=0.77V`
`E^(c-)._(Ce^(4+)|Ce^(3+))=1.61V`
On the basis of standard reduction potential `(E^(c-))`,
`E^(c-)` of `FegtE^(c-)` of `Ce`. So in such cell `Fe` acts as anode while `Ce` acts as cathode.
`E^(c-)._(cell)=(E^(c-)._(cathode)-E^(c-)._(anode ))_(red)`
`=1.61-0.77=0.84V`
Hence , the flow of current from cathode to anode `(` right to left `),` and current will decrease with time.