When heated `NH_3` is passed over `CuO` , gas evolved is

Options

A. `N_2`
B. `N_2 O`
C. `HNO_3`
D. `NO_2`

Explanation

To determine the gas evolved when heated ammonia (NH₃) is passed over copper(II) oxide (CuO), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**: When ammonia (NH₃) is heated and passed over copper(II) oxide (CuO), a reduction reaction occurs. In this reaction, ammonia acts as a reducing agent.

2. **Identifying the Products**: The copper(II) oxide (CuO) is reduced to copper (Cu), while ammonia (NH₃) is oxidized. The byproducts of this reaction include nitrogen gas (N₂) and water (H₂O).

3. **Writing the Balanced Chemical Equation**:
- The unbalanced reaction can be written as:
\[ 2 \text{NH}_3 + 3 \text{CuO} \rightarrow 3 \text{Cu} + 3 \text{H}_2\text{O} + \text{N}_2 \]
- This equation indicates that for every 2 moles of ammonia, 3 moles of copper(II) oxide are consumed, producing 3 moles of copper, 3 moles of water, and 1 mole of nitrogen gas.

4. **Identifying the Evolved Gas**: From the balanced equation, we can see that nitrogen gas (N₂) is one of the products formed during the reaction.

5. **Conclusion**: Therefore, the gas evolved when heated NH₃ is passed over CuO is nitrogen gas (N₂).

### Final Answer:
The gas evolved is nitrogen gas (N₂).

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