Cell reactions

Cell reactions

Na⁺ ions are attracted towards cathode, where they combine with the electrons and reduced to liquid sodium.

Cathode (reduction)

Na⁺ (l ) + e^- → Na (l)                                E^o = -2.71V

Similarly, Cl^– ions are attracted towards anode where they lose their electrons and oxidised to chlorine gas.

Anode (oxidation)

2Cl^- (l) → Cl₂ (g) + 2e^-                                  E^o = -1.36V

The overall reaction is,

2Na⁺ (l ) + 2Cl^- (l) → 2Na(l ) + Cl₂ (g )                        E^o = - 4.07V

The negative E^o value shows that the above reaction is a non spontaneous one. Hence, we have to supply a voltage greater than 4.07V to cause the electrolysis of molten NaCl.

In electrolytic cell, oxidation occurs at the anode and reduction occur at the cathode as in a galvanic cell, but the sign of the electrodes is the reverse i.e., in the electrolytic cell cathode is –ve and anode is +ve.