Question

Sodium is prepared by the electrolysis of molten $\mathrm{NaCl}$ but not by the electrolysis of its aqueous solution. Why?

Answer 1

• Electrolysis of aqueous $\mathrm{NaCl}$ (${\mathrm{Na}}^{2+}$ ions are not discharged at the cathode).
• Hydrogen is produced at the cathode. Water is reduced to hydroxide and hydrogen gas.
• The reduction potential of sodium is lower than in water.
• Sodium is a very reactive metal. On electrolysis, an aqueous solution of sodium chloride produces sodium at the cathode which reacts with water to form dihydrogen gas and NaOH in the solution.
• Therefore molten $\mathrm{NaCl}$ is used in most industries rather than aqueous $\mathrm{NaCl}$.