Electrolytic Cells And Electrolysis

In the electrolysis of aqueous NaCl (brine), water and NaCl both participate in the redox process.

At the cathode:
Reduction occurs.
Among Na⁺ and H₂O, H₂O gets reduced more easily:

So, gas is evolved at the cathode.

At the anode:
Oxidation occurs.
Between Cl⁻ and OH⁻, Cl⁻ gets oxidized more readily:

So, Cl₂ gas is released at the anode.

The correct answer is option (A): H₂ at cathode

In the extraction of highly reactive metals like aluminum or sodium, electrolysis is used. To make the process efficient and less energy-consuming, impurities such as cryolite (in the case of aluminum extraction) are added. These impurities help by lowering the melting point of the ore, thus:

• Reducing the energy required for electrolysis
• Making the process more economical and feasible

Hence, the correct purpose of adding impurity is to decrease the melting point of the ore.

The correct option is (D): to decrease the melting point of ore