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Cell Potential Formula

The driving force of the electron flow from anode to cathode shows a potential drop in the energy of the electrons moving into the wire.  The difference in potential energy between the anode and cathode is known as the cell potential in a voltaic cell.

Formula for cell potential is

E∘cellcell∘ = E∘reductionreduction∘ + E∘oxidationoxidation∘


Ecellcell = 0.0591n0.0591n log10 C2C1C2C1.

Problem 1: A concentration cell was created by immersing two silver electrodes in 0.05M and 0.1M AgNO3 solution. Write cell representation, cell reactions and find the EMF of the concentration cell.


The cell representation

Ag|AgNO3 (0.05M) || AgNO3 (0.1M)|Ag

At anode,

Ag →→ Ag+ (0.05M) + e

At cathode,

Ag+ (0.1M) + e →→ Ag

Net cell reaction is,

Ag+ (0.1M) →→ Ag+ (0.05M)

The EMF of a concentration cell,

Ecellcell = 0.0591n0.0591n log10 C2C1C2C1

Ecellcell = 0.059110.05911 log10

Ecellcell = 0.12 V

Question 2: If a concentration cell of the silver electrode is represented as,

Ag/Ag+ (0.00475 M) || Ag+ (0.043 M)/Ag.

An electrode of higher concentration having Ag+ (0.043 M) acts as cathode while the other silver electrode having Ag+ ion concentration (0.00475 M) acts as anode.


At anode,

Ag(s) →→ Ag+ + e

At cathode,

Ag+ + e →→ Ag(s)

The net reaction of the concentration cell is,

Ag+ (0.043 M) →→ Ag+ (0.00475 M)

The EMF of the concentration cell is,

Ecellcell = 0.0591n0.0591n log10 C2C1C2C1

Ecellcell = 0.059120.05912 log10 0.0430.004750.0430.00475

Ecellcell = 0.056 V



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