In Duma's method, the gas collected in nitrometer is :

Options

A. `N_(2)`
B. `NO`
C. `NH_(3)`
D. `H_(2)`

Explanation

### Step-by-Step Solution:

1. **Understanding Duma's Method**: Duma's method is a technique used for the estimation of nitrogen in organic compounds. It involves the combustion of the organic compound in the presence of cupric oxide (CuO).

2. **Reaction Setup**: In this method, the organic compound containing nitrogen is mixed with cupric oxide and heated in a furnace. The reaction can be represented as:
\[ \text{Organic Compound} + \text{CuO} \rightarrow \text{CO}_2 + \text{N}_2 + \text{H}_2\text{O} \]
This reaction produces carbon dioxide (CO₂), nitrogen (N₂), and water (H₂O).

3. **Collection of Gases**: The gases produced during the reaction, specifically nitrogen, are collected in a device known as a nitrometer. The nitrometer is designed to measure the volume of gases produced.

4. **Separation of Gases**: After the reaction, the mixture contains nitrogen, carbon dioxide, and water vapor. To obtain pure nitrogen gas, it is necessary to remove CO₂ and H₂O. This is done using:
- **KOH (Potassium Hydroxide)**: This absorbs carbon dioxide.
- **HgCl₂ (Mercury(II) Chloride)**: This absorbs water vapor.

5. **Final Collection**: After the absorption of CO₂ and H₂O, the remaining gas in the nitrometer is pure nitrogen (N₂).

### Conclusion:
Thus, in Duma's method, the gas collected in the nitrometer is nitrogen (N₂).

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