Which of the following radicals evolve gas or vapour when treated with dil HCl?

Options

A. (a) `SO_(3)^(2-)`
B. (b) `C_(2)O_(4)^(2-)`
C. (c) `CH_(3)COO^(-)`
D. (d) `HCO_(3)^(-)`

Answer

To determine which of the given radicals evolve gas or vapor when treated with dilute HCl, we will analyze each option step by step.

### Step 1: Analyze SO3^2- (Sulfite Ion)
- **Compound Example**: Sodium sulfite (Na2SO3).
- **Reaction with Dilute HCl**:
\[ \text{Na}_2\text{SO}_3 + 2 \text{HCl} \rightarrow 2 \text{NaCl} + \text{H}_2\text{O} + \text{SO}_2 \uparrow \]
- **Gas Evolved**: Sulfur dioxide (SO2) is produced.
- **Conclusion**: SO3^2- evolves gas when treated with dilute HCl.

### Step 2: Analyze C2O4^2- (Oxalate Ion)
- **Compound Example**: Sodium oxalate (Na2C2O4).
- **Reaction with Dilute HCl**:
\[ \text{Na}_2\text{C}_2\text{O}_4 + 2 \text{HCl} \rightarrow \text{H}_2\text{C}_2\text{O}_4 + 2 \text{NaCl} \]
- **Gas Evolved**: No gas or vapor is produced; only oxalic acid (H2C2O4) and sodium chloride (NaCl) are formed.
- **Conclusion**: C2O4^2- does not evolve gas when treated with dilute HCl.

### Step 3: Analyze CH3COO^- (Acetate Ion)
- **Compound Example**: Sodium acetate (CH3COONa).
- **Reaction with Dilute HCl**:
\[ \text{CH}_3\text{COONa} + \text{HCl} \rightarrow \text{NaCl} + \text{CH}_3\text{COOH} \]
- **Gas Evolved**: No gas or vapor is produced; only acetic acid (CH3COOH) and sodium chloride (NaCl) are formed.
- **Conclusion**: CH3COO^- does not evolve gas when treated with dilute HCl.

### Step 4: Analyze HCO3^- (Bicarbonate Ion)
- **Compound Example**: Sodium bicarbonate (NaHCO3).
- **Reaction with Dilute HCl**:
\[ \text{NaHCO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{CO}_2 \uparrow + \text{H}_2\text{O} \]
- **Gas Evolved**: Carbon dioxide (CO2) is produced.
- **Conclusion**: HCO3^- evolves gas when treated with dilute HCl.

### Final Conclusion
- The radicals that evolve gas or vapor when treated with dilute HCl are:
- **A: SO3^2- (Sulfite Ion)** - evolves SO2 gas.
- **D: HCO3^- (Bicarbonate Ion)** - evolves CO2 gas.

### Answer
The correct options are **A and D**.

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