Reddish brown gas is obtained when the following are treated with conc `H_(2)SO_(4)`

Options

A. `Br^(Θ)`
B. `NO_(2)^(Θ)`
C. `NO_(3)^(Θ)`
D. `I^(-)`

Explanation

To determine which ions produce a reddish-brown gas when treated with concentrated sulfuric acid (H₂SO₄), we will analyze each ion step by step.

### Step 1: Analyzing Bromide Ion (Br⁻)
1. **Take a salt containing bromide**: For example, potassium bromide (KBr).
2. **Reaction with concentrated H₂SO₄**:
\[ \text{KBr} + \text{H}_2\text{SO}_4 \rightarrow \text{K}_2\text{SO}_4 + \text{HBr} \]
3. **Identify the gas produced**: HBr is produced, which can further decompose upon heating to release bromine gas (Br₂), which is reddish-brown.

**Conclusion**: The bromide ion does produce a reddish-brown gas.

### Step 2: Analyzing Nitrite Ion (NO₂⁻)
1. **Take a salt containing nitrite**: For example, sodium nitrite (NaNO₂).
2. **Reaction with concentrated H₂SO₄**:
\[ \text{NaNO}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + \text{HNO}_2 \]
3. **Decomposition of HNO₂**:
\[ 3 \text{HNO}_2 \rightarrow \text{HNO}_3 + 2 \text{NO} + \text{H}_2\text{O} \]
4. **Identify the gas produced**: The NO gas produced can react with oxygen to form NO₂, which is reddish-brown.
\[ 2 \text{NO} + \text{O}_2 \rightarrow 2 \text{NO}_2 \]

**Conclusion**: The nitrite ion does produce a reddish-brown gas.

### Step 3: Analyzing Nitrate Ion (NO₃⁻)
1. **Take a salt containing nitrate**: For example, sodium nitrate (NaNO₃).
2. **Reaction with concentrated H₂SO₄**:
\[ \text{NaNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NaHSO}_4 + \text{HNO}_3 \]
3. **Decomposition of HNO₃**:
\[ 4 \text{HNO}_3 \rightarrow 2 \text{NO}_2 + 2 \text{H}_2\text{O} + \text{O}_2 \]

**Conclusion**: The nitrate ion does produce a reddish-brown gas.

### Step 4: Analyzing Iodide Ion (I⁻)
1. **Take a salt containing iodide**: For example, potassium iodide (KI).
2. **Reaction with concentrated H₂SO₄**:
\[ \text{KI} + \text{H}_2\text{SO}_4 \rightarrow \text{K}_2\text{SO}_4 + \text{HI} \]
3. **Identify the gas produced**: HI does not produce a reddish-brown gas upon decomposition.

**Conclusion**: The iodide ion does not produce a reddish-brown gas.

### Final Conclusion:
The ions that produce a reddish-brown gas when treated with concentrated H₂SO₄ are:
- Bromide ion (Br⁻)
- Nitrite ion (NO₂⁻)
- Nitrate ion (NO₃⁻)

The iodide ion (I⁻) does not produce a reddish-brown gas.

---