Which one is used in the manufacture of mirror

Options

A. Red lead (litharge)
B. Ammoniacal `AgNO_3`
C. Ammoniacal `AgNO_3` + Red lead
D. Ammoniacal `AgNO_3 + HCHO`

Explanation

To determine which compound is used in the manufacture of mirrors, we need to analyze the options provided and understand the chemical processes involved.

### Step-by-Step Solution:

1. **Identify the Compounds**: The question lists several compounds related to the manufacture of mirrors. These include:
- Red lead
- Ammoniacal silver nitrate
- Ammoniacal silver nitrate plus red lead
- Ammoniacal silver nitrate plus formaldehyde (SCHO)

2. **Understand the Role of Silver Nitrate**: Silver nitrate (AgNO₃) is a key compound in the process of making mirrors. It is used because it can be reduced to metallic silver, which is reflective.

3. **Recognize the Importance of Formaldehyde**: In the context of mirror-making, formaldehyde (HCHO) acts as a reducing agent. When mixed with ammoniacal silver nitrate, it reduces silver ions (Ag⁺) to metallic silver (Ag), which deposits on the surface, creating a reflective layer.

4. **Evaluate the Options**:
- Red lead is not typically used in mirror-making.
- Ammoniacal silver nitrate alone may not be sufficient without a reducing agent.
- Ammoniacal silver nitrate plus red lead does not serve the purpose of reducing silver ions.
- Ammoniacal silver nitrate plus formaldehyde is the correct combination for producing a mirror, as it effectively reduces silver ions to metallic silver.

5. **Conclusion**: The compound used in the manufacture of mirrors is **ammoniacal silver nitrate plus formaldehyde (SCHO)**.

### Final Answer:
**Ammoniacal silver nitrate plus formaldehyde (SCHO)** is used in the manufacture of mirrors.

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