Question

In the electrochemical reaction ; 2Fe3+ + Zn = Zn2+ +2 Fe2+, increasing the concentration of Fe2+ results in

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Answer 1

On increasing the concentration of Fe⁺² the emf of the cell decreases

• The emf of the cell is given by the Nernst equation

           $E=E_{0}-\frac{0.059}{n} log_{10} \frac{[Fe^{+2}]}{[Zn]}$

• The number of electron taking part in the reaction is two

           $E=E_{0}-\frac{0.059}{2} log_{10} \frac{[Fe^{+2}]}{[Zn]}$

• From the equation it is clear that on increasing the concentration of Fe⁺²  the negative value in the equation increases which has to be subtacted from the standard emf of the cell.

• So the emf of the cell decreases as the concentration of Fe⁺² is increased.