In the Down's method for the extraction of sodium, the melting point of the electrolyte is lowered by adding:-

Options

A. Potassium chloride
B. Calcium chloride
C. Potassium fluoride
D. Both calcium chloride and potassium fluoride

Answer

To solve the question regarding the Down's method for the extraction of sodium and the lowering of the melting point of the electrolyte, we can follow these steps:

### Step 1: Understand the Down's Method
The Down's method is a process used for the extraction of sodium from its molten salt. It involves the electrolysis of a mixture of sodium chloride (NaCl) and calcium chloride (CaCl2) or potassium chloride (KCl).

**Hint:** Familiarize yourself with the Down's method and its purpose in sodium extraction.

### Step 2: Identify the Electrolyte
In the Down's process, the electrolyte is typically a mixture of sodium chloride and another salt that helps to lower the melting point. The common salts used for this purpose are calcium chloride (CaCl2) and potassium chloride (KCl).

**Hint:** Recall the role of electrolytes in electrolysis and how their melting points can affect the efficiency of the process.

### Step 3: Determine the Additive
The question asks which substance is added to lower the melting point of the electrolyte. Calcium chloride (CaCl2) is known to be effective in this role. Potassium chloride (KCl) can also be used, but the question specifically highlights the lowering of the melting point.

**Hint:** Think about common salts that are used to lower melting points in chemical processes.

### Step 4: Choose the Correct Option
Based on the understanding that both calcium chloride and potassium chloride can be added to lower the melting point of the electrolyte, we can conclude that the correct answer is option D, which includes both CaCl2 and KCl.

**Hint:** Review the options provided in the question to confirm which one includes the correct additives.

### Final Answer
The melting point of the electrolyte in the Down's method is lowered by adding calcium chloride (CaCl2) and potassium chloride (KCl). Therefore, the correct option is D.