The following electrochemical cell is represented as `:`
`Pt(1)|Hg^(2+),Hg_(2)^(2+)(a=1)||Ce^(4+),Ce^(3+)(a=1)|Pt(2)`
`a.` If an ammeter is connected between two platinum electrodes, predict the direction of flow of current.
`b.` Will the current decrease or increase with time?
Given `:E^(c-)._(2Hg^(2+)|Hg_(2)^(2+))=0.92V,E^(c-)._(Ce^(4+)//Ce^(3+))=1.61V`

Explanation

The elctrode reactions are as follows `:`
Anode reaction `:Hg_(2)^(2+) rarr 2Hg^(2+)+cancel(2e^(-) (` oxidation `)`
Cathode reaction `:`
`2Ce^(4+)+cancel(2e^(-)) rarr 2Ce^(3+) (` Reduction `)`
`ulbar(Cell reaction :Hg_(2)^(2+),2Ce^(4+) rarr2Hg^(2+)+2Ce^(3+))`
`:. E^(c-)._(cell)=(E^(c-)._(reduction))_(c)-(E^(c-)._(reduction))_(a)`
`=1.61V-0.92V=0.69V`
Since `E^(c-)` cell is positive, the cell reaction is feasible or spontaneous. ltbr. Current in electrochemical cell flows from cathode to anode whereas the electrons flow from anode to cathode.
So the current in the circuit will flow from `Pt(2)(` cathode`)` to `Pt(1)(` anode `).`
`b.` With the passage of time, `EMF` of the cell will drecrease and so the current will also decrease in the circuit.