The reference calomel electrode is made from which of the following ?

Options

A. `ZnCl_(2)`
B. `CuSO_(4)`
C. `Hg_(2)Cl_(2)`
D. `HgCl_(2)`

Explanation

To solve the question "The reference calomel electrode is made from which of the following?" we can follow these steps:

### Step 1: Understand the Question
The question is asking for the material used to construct a reference calomel electrode.

### Step 2: Identify the Options
The options provided are:
1. Zinc chloride
2. Copper sulphate
3. Mercurous chloride
4. Mercuric chloride

### Step 3: Recall Information about Calomel Electrode
A calomel electrode, also known as a saturated calomel electrode (SCE), is a type of reference electrode used in electrochemistry. It is important to know what materials are typically used in the construction of this electrode.

### Step 4: Determine the Correct Material
The calomel electrode is specifically made from **mercurous chloride**, which is represented chemically as Hg2Cl2. This is the key material that defines the calomel electrode.

### Step 5: Eliminate Incorrect Options
- **Zinc chloride**: Not used in calomel electrodes.
- **Copper sulphate**: Not used in calomel electrodes.
- **Mercuric chloride**: This is different from mercurous chloride and is not used for calomel electrodes.

### Step 6: Conclude the Answer
The correct answer is **Mercurous chloride (Hg2Cl2)**, which corresponds to option number 3.

### Final Answer:
The reference calomel electrode is made from **Mercurous chloride (Hg2Cl2)**.

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