Question

In Down’s process, a small amount of KCl is added to NaCl :
(A) to decrease the melting point of NaCl
(B) to increase the electrical conductivity
(C) to maintain electrical contact
(D) to prevent the oxidation of sodium metal formed

Answer 1

Hint: The NaCl has a very high melting point. It melts at $1074 K$ temperature which is very difficult to achieve. The electrical conductivity is sufficiently achieved by other reagents. KCl and KF mixture added to NaCl to overcome the drawback of its very high melting point.

Complete step by step solution:
Let us see what is down’s process and what is its function.
It is the process for extracting sodium by electrolysis of molten sodium chloride (NaCl).
In Down’s cell, the carbon acts as anode and the iron acts as the cathode. The magnesium chloride is the electrolyte which is heated to liquid.
The Sodium chloride has a high melting point of $1074 K$. The sodium can be obtained by electrolysis of sodium chloride in the molten state. The KCl and even KF are added to decrease the melting point of the mixture. This is added so the sodium could be obtained at low temperature.

Thus, the option (A) is the correct answer.

Note: It is an electrochemical method that is used to produce sodium metal and the chlorine gas from sodium chloride. The Sodium is produced at the cathode while the chlorine gas is released at the anode. It is a very good method for the preparation of sodium.