With which of the following metal dil. `HNO_3` produces nitrous oxide ?

Options

A. Ag
B. Zn
C. Cu
D. Fe

Answer

To determine which metal reacts with dilute HNO3 to produce nitrous oxide (N2O), we can analyze the electropositive character of the metals given in the question. The metals in question are silver (Ag), zinc (Zn), copper (Cu), and iron (Fe).

### Step-by-Step Solution:

1. **Identify the Metals**: The metals provided are silver (Ag), zinc (Zn), copper (Cu), and iron (Fe).

2. **Understand the Reaction**: The general reaction of a metal with dilute nitric acid (HNO3) can be represented as:
\[ \text{Metal} + \text{HNO}_3 \rightarrow \text{Salt} + \text{H}_2 + \text{N}_2\text{O} \]
However, the formation of nitrous oxide (N2O) specifically occurs with more electropositive metals.

3. **Electropositive Character**: The electropositive character of metals determines their reactivity with acids. The more electropositive a metal is, the more likely it is to produce nitrous oxide when reacting with dilute HNO3.

4. **Electrochemical Series**: Based on the electrochemical series, we can rank the metals in order of their electropositivity:
- Zinc (Zn) - most electropositive
- Iron (Fe)
- Copper (Cu)
- Silver (Ag) - least electropositive

5. **Reactions with Dilute HNO3**:
- **Zinc**:
\[ \text{Zn} + 4 \text{HNO}_3 \rightarrow \text{Zn(NO}_3)_2 + 2 \text{H}_2\text{O} + \text{N}_2\text{O} \]
Zinc reacts with dilute HNO3 to produce nitrous oxide.
- **Copper**:
\[ \text{Cu} + 2 \text{HNO}_3 \rightarrow \text{Cu(NO}_3)_2 + \text{H}_2 \]
Copper does not produce N2O; it produces hydrogen gas instead.
- **Iron**:
\[ \text{Fe} + 2 \text{HNO}_3 \rightarrow \text{Fe(NO}_3)_2 + \text{H}_2 \]
Iron also does not produce N2O; it produces hydrogen gas.
- **Silver**:
\[ 2 \text{Ag} + 2 \text{HNO}_3 \rightarrow 2 \text{AgNO}_3 + \text{H}_2 \]
Silver reacts similarly and does not produce N2O.

6. **Conclusion**: Among the metals listed, only zinc reacts with dilute HNO3 to produce nitrous oxide (N2O). Therefore, the correct answer is **Zinc (Zn)**.

### Final Answer:
**Zinc (Zn)** produces nitrous oxide (N2O) when reacted with dilute HNO3.