`CI^(Θ)`is confirmed by (a) ____.

Answer

To confirm the presence of chloride ions (Cl⁻), we can perform the Chromyl Chloride Test. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Preparation of the Mixture:**
- Take a sample of a chloride salt, such as sodium chloride (NaCl).
- Add concentrated sulfuric acid (H₂SO₄) to the chloride salt in a test tube.

2. **Addition of Potassium Dichromate:**
- Introduce potassium dichromate (K₂Cr₂O₇) to the mixture of the chloride salt and sulfuric acid.

3. **Heating the Mixture:**
- Heat the mixture gently. During this process, the chloride ions react with potassium dichromate in the presence of sulfuric acid.

4. **Observation of Chromyl Chloride Vapors:**
- As the mixture is heated, red-brown vapors of chromyl chloride (CrO₂Cl₂) are produced. This indicates the presence of chloride ions in the sample.

5. **Confirmation of Chromyl Chloride:**
- To further confirm the presence of chromyl chloride, the red-brown vapors can be reacted with sodium hydroxide (NaOH). This reaction will yield sodium chromate (Na₂CrO₄) and water (H₂O).

6. **Formation of Yellow Precipitate:**
- Next, add lead acetate (Pb(CH₃COO)₂) to the solution containing sodium chromate. This will result in the formation of a yellow precipitate of lead chromate (PbCrO₄), confirming the presence of chromyl chloride and, consequently, chloride ions.

### Final Answer:
The presence of chloride ions (Cl⁻) is confirmed by the **Chromyl Chloride Test**.

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