When `K_(2)Cr_(2)O_(7)` is heated with conc. `H_(2)SO_(4)` and soluble chloride such as KCl :

Options

A. red vapours of `CrO_(2)Cl_(2)` are evolved
B. `Cl^(-)` ion is oxidized to `Cl_(2)` gas
C. `CrCl_(3)` is formed
D. `Cr_(2)Cl_(2)` is formed

Explanation

**Step-by-Step Solution:**

1. **Understanding the Reaction**: When potassium dichromate (K₂Cr₂O₇) is heated with concentrated sulfuric acid (H₂SO₄) and a soluble chloride like potassium chloride (KCl), a specific reaction occurs that is used to detect the presence of chloride ions.

2. **Reaction Components**: The main components involved in this reaction are:
- Potassium Dichromate (K₂Cr₂O₇)
- Concentrated Sulfuric Acid (H₂SO₄)
- Potassium Chloride (KCl)

3. **Heating the Mixture**: When the mixture of K₂Cr₂O₇, H₂SO₄, and KCl is heated, the concentrated sulfuric acid acts as a dehydrating agent and facilitates the reaction between dichromate ions and chloride ions.

4. **Formation of Chromyl Chloride**: The reaction leads to the formation of chromyl chloride (CrO₂Cl₂), which is characterized by its red vapors. The chloride ions from KCl are oxidized, and the chromium from K₂Cr₂O₇ is reduced.

5. **By-products of the Reaction**: Along with chromyl chloride, other by-products such as potassium bisulfate (KHSO₄) and water (H₂O) are also formed during this reaction.

6. **Conclusion**: The primary observation from this reaction is the evolution of red vapors of chromyl chloride (CrO₂Cl₂), confirming the presence of chloride ions in the sample.

**Final Answer**: The correct option is **1. Red vapors of CrO₂Cl₂ are evolved.**

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