What change is observed on copper surface due to the action of air and moisture?

Options

A. Appearance of brown powder
B. Appearance of green powder
C. Formation of black coating
D. Formation of silver flakes

Answer

To answer the question about the changes observed on the copper surface due to the action of air and moisture, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When copper is exposed to air (which contains oxygen) and moisture (water), it undergoes a chemical reaction. This process is known as corrosion.

2. **Identifying the Products**:
- The reaction of copper with moisture and carbon dioxide (from the air) leads to the formation of copper hydroxide (Cu(OH)₂) and copper carbonate (CuCO₃).
- The copper carbonate formed is typically a green compound.

3. **Observing the Change**:
- The visible change on the surface of copper due to this reaction is the appearance of a greenish layer or powder. This is often referred to as patina.

4. **Choosing the Correct Option**:
- From the options provided:
- A) Appearance of brown powder
- B) Appearance of green powder
- C) Formation of black coating
- D) Formation of silver flakes
- The correct answer is **B) Appearance of green powder**, as this reflects the corrosion products formed on the copper surface.

### Final Answer:
The change observed on the copper surface due to the action of air and moisture is the **appearance of green powder**.

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