Brass gets discoloured in air because of the presence of which of the following gases in air?

Options

A. Carbon dioxide
B. Oxygen
C. Hydrogen sulphide
D. Nitrogen

Explanation

To solve the question regarding why brass gets discolored in air, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Brass**:
- Brass is an alloy primarily made of copper and zinc. It is known for its shiny appearance and is commonly used in various applications.

2. **Identifying the Problem**:
- The question asks why brass discolors when exposed to air. This discoloration is a chemical change that occurs over time.

3. **Researching the Cause of Discoloration**:
- When brass is exposed to air, it can react with certain gases present in the atmosphere. One significant gas that can cause discoloration is hydrogen sulfide (H₂S).

4. **Chemical Reaction**:
- Hydrogen sulfide is a gas that can react with the copper present in brass. This reaction leads to the formation of copper sulfide, which has a darker color than the original brass, causing the discoloration.

5. **Conclusion**:
- Therefore, the discoloration of brass in air is primarily due to the presence of hydrogen sulfide gas.

### Final Answer:
Brass gets discolored in air because of the presence of hydrogen sulfide (H₂S) in the air.

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