What type of cell is a lead storage batt...

What type of cell is a lead storage battery? Write the anode and the cathode reactions and the overall cell reaction occurring in the use of a lead storage battery?

Text Solution

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Lead storage battery is a secondary cell.
The cell reactions when the battery is in use are given below:
Anode:
`Pb(s)+SO_4^(2-) (aq) to PbSO_4(s)+2e^(-)`
Cathode:
`PbO_2(s)+SO_4^(2-) (aq)+4H^(+) (aq) +2e^(-) to PbSo_4(s)+2H_2O(l)`
i.e., overall cell reaction consisting of cathode and anode reactions is:
`Pb(s)+PbO_2(s)+2H_2SO_4(aq)to2PbSO_4(s)+2H_2O(l)`
While, charging the battery the electrode reactions are reverse of those that occur during discharge.

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In lead storage battery, at cathode

`PbO_(2)` is reduced

lead is oxidised

`PbSO_(4)` is ionized

Lead ions combine with `Cl^(-)` ions.

The cathode reaction in the dry cell will be

`Zn(s)rarr Zn^(+2)+2e^-`

`MnO_2`+NH_4^+ +e^- rarr MnO(OH)+NH_3`

`Zn(Hg)+2OH^- rarr ZnO(s)+H_2O+2e^-`

`MnO(OH)+NH_3 rarr MnO_2 +NH_4^+ +2e^-`.

The cathode reaction in the dry cell will be :

`Zn(s) rarr Zn^(2+)+2e^(-)`

`MnO_(2)+NH_(4)^(+)-e^(-) rarr MnO(OH)+NH_(3)`

`Zn(Hg)+2OH^(-) rarr ZnO(s)+H_(2)O+2e^(-)`

`MnO(OH)+NH_(3) rarr MnO_(2)+NH_(4)^(+)+2e^(-)`.