Question

Identify the substances which are usually liberated at the electrodes during the process of electrolysis of aqueous $NaCl$.

• A. Zinc and chlorine
• B. Sodium and hydrogen
• C. Oxygen and chlorine
• D. Hydrogen and chlorine

Answer 1

The correct option is D Hydrogen and chlorine

Electrolysis of aqueous sodium chloride yields hydrogen and chlorine, with aqueous sodium hydroxide remaining in solution.

The reason for the difference is that the reduction of Na+ (E° = –2.7 v) is energetically more difficult than the reduction of water (–1.23 v).

The reaction at the cathode is:

$H_{2}O\left(l\right)+2e^{-}\to H_2\left(g\right)+2O{H}^{-}$

The reaction at the anode is:

$C{l}^{-}\to 1/2C{l}_2\left(g\right)+e^{-}$

The overall reaction is as follows:

$NaCl\left(aq\right)+H_{2}O\left(l\right)\to N{a}^{+}\left(aq\right)+O{H}^{-}\left(aq\right)+H_2\left(g\right)+1/2C{l}_2\left(g\right)$