Question

Match the following based on the products formed at cathode and anode during the electrolysis of NaCl.

• A. $H_2$ gas
• B. $O_2$gas
• C. ${\mathrm{Cl}}_2$ gas

Answer 1

During the electrolysis of (\text{NaCl}\), irrespective of concentration, the product formed at the cathode is always hydrogen.

In case of dilute NaCl solution, ${\text{H}}_2\text{O}$ is preferentially oxidised at anode, since ${\text{H}}_2\text{O}$ is higher in electrochemical series of anions than ${\text{Cl}}^{-}$.

But, ${\text{H}}_2\text{O}$ and ${\text{Cl}}^{-}$ are very close in electrochemical series of anions.

Though ${\text{H}}_2\text{O}$ is above ${\text{Cl}}^{-}$ but ${\text{Cl}}^{-}$ ions are more in numbers than ${\text{H}}_2\text{O}$ molecules in a concentrated $\text{NaCl}$ solution.

This alter the preferential oxidation at anode and ${\text{Cl}}^{-}$ ions get oxidised at anode in case of concentrated $\text{NaCl}$ solution.