Question

In Down’s process for the manufacture of sodium,$CaC{{l}_{2}}$ is added to:
(A) decreasing the melting point
(B) increase the melting point
(C) decrease the interionic interactions
(D) increase the interionic interactions

Answer 1

Hint: The Down’s process involves electrolysis of molten sodium chloride. The melting point of only sodium chloride is very high and therefore not feasible.

Complete step by step answer:
Sodium and chlorine are very important industrial raw materials that are then used to manufacture a variety of products. We know that sodium is also used in nuclear reactors and more than the metal itself, salts of sodium are widely used to produce many things such as toothpaste, which uses sodium fluoride as one of its ingredients. Chlorine acts as a disinfectant in the water that we generally use in our homes; apart from that it is also used as a raw material in chemical and textile industries.
So, production of this metal and non-metal has to be carried out on an industrial scale so as to cope up with their rising demands. Down’s process is the most popular industrial method used to manufacture both sodium and chlorine. The mechanism involves the electrolysis of molten sodium chloride, which results in the release of sodium at cathode and chlorine at anode respectively. Now, this salt is abundantly found in our oceans and therefore its collection is both efficient and economically feasible for industries.
The only problem Down’s process encounters is the high melting point of sodium chloride, which is around$800{}^\circ C$. First of all, it is not feasible for industries to keep up this temperature for long and second, a sodium fog is formed which mixes with the molten sodium chloride, making it extremely difficult to separate. This problem is tackled by adding calcium chloride to the mixture in a ratio of 1:2 ($NaCl:CaC{{l}_{2}}$). The melting point of this particular mixture is around $600{}^\circ C$ and solves both the above listed problems.
So, the correct answer is “Option A”.

Note: The ratio of calcium chloride to sodium chloride given above is an experimentally calculated result and therefore offers the maximum chances for solving the mentioned problem. Any other composition would not have the same effect.
Even if calcium chloride is mixed with sodium chloride, we can easily separate the metals calcium and sodium because of the significant difference in their densities.