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On the basis of standard electrode potential values, suggest which of the following reactions would take place? (Consult the book for E^{\Theta } value).

(i) Cu + Zn^{2+}\rightarrow Cu^{2+} + Zn
(ii) Mg + Fe^{2+}\rightarrow Mg^{2+} + Fe
(iii) Br_{2} + 2Cl^{-}\rightarrow Cl_{2} + 2Br^{-}
(iv) Fe + Cd^{2+}\rightarrow Cd + Fe^{2+}

Answers (1)

If a reaction might take place or not is dependent on the net cell EMF of the cell. The equation for the same is


In option (ii) it is clearly visible that, the reaction can take place as Mg has a more negative value of E^{^{\circ}}_{cell}. Hence, Mg is oxidised by losing electron and iron is reduced by gaining an electron.

Mg + Fe^{2+}\rightarrow Mg^{2+} + Fe

We can say that Fe undergoes reduction and Mg undergoes oxidation,






E^{^{\circ}}_{cell}=-0.44- \left (-2.36 \right )V



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