Electrolysis

The electrolysis of aqueous NaCl (sodium chloride) solution results in the following products at the cathode and anode:

Cathode: H2 (hydrogen gas) is produced. Anode: Cl2 (chlorine gas) is produced.

Therefore, the correct answer is H2, Cl2.

In the process of extracting aluminum through the electrolysis of alumina, cryolite (Na₃AlF₆) plays a crucial role. Here is why cryolite is added:

1. Melting Point Reduction: Alumina (Al₂O₃) has a very high melting point of approximately 2072°C. Cryolite serves to significantly lower this melting point to around 900°C to 1000°C, making the process more energetically feasible and cost-effective.

2. Solution Formation: While cryolite's primary purpose is to lower the melting point, it also acts as a solvent, allowing alumina to dissolve within the molten cryolite. This creates a fluid mixture that aids in the efficient conduction of electricity during electrolysis.

3. Electrical Conductivity: Cryolite enhances the electrical conductivity of the solution, facilitating more efficient passage of electric current required for aluminum extraction.

4. Correct Choice: From the given options, the primary reason for adding cryolite is to "Lower the melting point of alumina."