Copper on exposure to air reacts with moisture and `CO_(2)` to develop a green layer which is

Options

A. basic copper carbonate
B. copper sulphate
C. copper carbonate
D. copper nitrate.

Explanation

To solve the question about the green layer that develops on copper when exposed to air and moisture, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- Copper reacts with moisture (water) and carbon dioxide (CO₂) present in the air. This reaction leads to the formation of a green layer on the surface of the copper.

2. **Identifying the Compounds Involved**:
- The main components involved in the reaction are:
- Copper (Cu)
- Water (H₂O)
- Carbon Dioxide (CO₂)
- Oxygen (O₂) from the air

3. **Writing the Reaction**:
- The reaction can be simplified to show how copper reacts with these components. The overall reaction can be represented as:
\[ 2 \text{Cu} + 2 \text{H}_2\text{O} + \text{CO}_2 \rightarrow \text{Cu}_2\text{(OH)}_2\text{CO}_3 \]
- Here, \(\text{Cu}_2\text{(OH)}_2\text{CO}_3\) is the compound formed, which is known as basic copper carbonate.

4. **Identifying the Green Layer**:
- The green layer that forms on copper is primarily due to the formation of basic copper carbonate, which is represented by the formula \(\text{Cu}_2\text{(OH)}_2\text{CO}_3\).

5. **Analyzing the Options**:
- Given the options:
- A) Basic copper carbonate
- B) Copper sulfate
- C) Copper carbonate
- D) Copper nitrate
- Since we have established that the green layer is due to basic copper carbonate, we can conclude that option A is the correct answer.

### Final Answer:
The green layer that develops on copper when exposed to air and moisture is **basic copper carbonate**.

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