which one of the following salts will evolve halogen on treatment with conc. `H_(2)SO_(4)` ?

Options

A. `NaCI`
B. `CaCI_(2)`
C. `NaBr`
D. `KI`

Explanation

To determine which of the following salts will evolve halogen on treatment with concentrated H₂SO₄, we will analyze each option provided: NaCl, CaCl₂, NaBr, and KI.

### Step-by-Step Solution:

1. **Analyze NaCl with H₂SO₄:**
- When sodium chloride (NaCl) reacts with concentrated sulfuric acid (H₂SO₄), the reaction can be represented as:
\[ \text{NaCl} + \text{H}_2\text{SO}_4 \rightarrow \text{NaHSO}_4 + \text{HCl} \]
- In this reaction, hydrochloric acid (HCl) is produced, but no halogen gas is evolved. Therefore, NaCl does not evolve halogen.

2. **Analyze CaCl₂ with H₂SO₄:**
- Calcium chloride (CaCl₂) reacts with concentrated sulfuric acid as follows:
\[ \text{CaCl}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{CaHSO}_4 + \text{HCl} \]
- Similar to NaCl, this reaction produces HCl and does not evolve any halogen gas. Thus, CaCl₂ does not evolve halogen.

3. **Analyze NaBr with H₂SO₄:**
- When sodium bromide (NaBr) reacts with concentrated sulfuric acid, the reaction can be represented as:
\[ \text{NaBr} + \text{H}_2\text{SO}_4 \rightarrow \text{NaHSO}_4 + \text{Br}_2 + \text{H}_2\text{O} \]
- In this case, bromine gas (Br₂) is evolved. Therefore, NaBr does evolve halogen.

4. **Analyze KI with H₂SO₄:**
- Potassium iodide (KI) reacts with concentrated sulfuric acid as follows:
\[ \text{KI} + \text{H}_2\text{SO}_4 \rightarrow \text{KHSO}_4 + \text{I}_2 + \text{H}_2\text{O} \]
- Here, iodine gas (I₂) is evolved. Thus, KI also evolves halogen.

### Conclusion:
The salts that evolve halogen on treatment with concentrated H₂SO₄ are NaBr and KI. Therefore, the correct options are:
- **C. NaBr**
- **D. KI**