Question

Arrange the following according to the instructions: ${\mathrm{Mg}}^{+2},{\mathrm{Cu}}^{+2},{\mathrm{Na}}^{+},{\mathrm{H}}^{+}$ (In the order of preferential discharge at the cathode).

Answer 1

Electrochemical series also known as activity series which describe the arrangement of elements in order of their increasing electrode potential.

$\underset{\mathrm{Increasing}\mathrm{ease}\mathrm{of}\mathrm{discharge}}{\overset{\mathrm{K}\mathrm{Na}\mathrm{Ca}\mathrm{Mg}\mathrm{Al}\mathrm{Zn}\mathrm{Fe}\mathrm{H}\mathrm{Cu}\mathrm{Ag}}{\to }}$

1. The elements in the lower position gets discharged more easily during electrolysis.

2. The cations can easily gain electrons for the elements.

3. ${\mathrm{Cu}}^{+2}$ discharged more preferentially at the cathode.

4. ${\mathrm{Na}}^{+}$discharged least preferentially at the cathode.

Order of preferential discharge at the cathode :

${\mathrm{Cu}}^{+2}>{\mathrm{H}}^{+}>{\mathrm{Mg}}^{+2}>{\mathrm{Na}}^{+}$