Question

During the electrolysis of a saturated solution of sodium chloride, where is : (a) chlorine formed ? (b) hydrogen formed ? (c) sodium hydroxide formed ?

Answer 1

a) chlorine formed on anode
b) hydrogen formed on cathode
c) sodium hydroxide gets stored near cathode

Answer 2

Answer: For a) Chlorine is formed at anode.

For b) Hydrogen gas is formed at cathode.

For c) Sodium hydroxide is formed near cathode.

Explanation: Electrolysis of aqueous NaCl results in hydrogen gas and chloride gas. At anode, chloride $(Cl^-)$ is oxidized to chlorine. The ion-selective membrane allows the counterion which is  $Na^+$ to flow across freely, but prevents anions such as hydroxide $(OH^-)$ and chloride from diffusing across. At cathode, water is reduced to hydroxide and hydrogen gas. The net result is the electrolysis of an aqueous solution of NaCl into useful products like sodium hydroxide (NaOH) and chlorine gas.

At Anode:      $H_2O(l)+2e^-\rightarrow H_2(g)+2OH^-$

At Cathode:   $Cl^-\rightarrow \frac{1}{2}Cl_2(g)+e^-$

Net reaction: $NaCl(aq)+H_2O(l)\rightarrow Na^+(aq)+OH^-(aq)+H_2(g)+\frac{1}{2}Cl_2(g)$