Which of the following statements is/are correct for chromyl chloride test ?

Options

A. Formation of chromyl chloride vapour
B. Liberation of chlorine gas
C. Formation of lead chromate
D. Formation of reddis-brown vapour

Explanation

To determine which statements are correct regarding the chromyl chloride test, we will analyze the test step by step.

### Step-by-Step Solution:

1. **Understanding the Chromyl Chloride Test**:
- The chromyl chloride test is primarily used to detect the presence of chloride ions (Cl-) in a sample.
- The test involves the reaction of potassium dichromate (K2Cr2O7) with hydrochloric acid (HCl) to produce chromyl chloride (CrO2Cl2), which is a reddish-brown vapor.

2. **Reaction Involved**:
- The reaction can be represented as:
\[ K_2Cr_2O_7 + 6HCl \rightarrow 2CrO_2Cl_2 + 2KCl + 3H_2O \]
- Here, chromyl chloride is formed, which is indicative of the presence of chloride ions.

3. **Observations**:
- The formation of reddish-brown vapor (CrO2Cl2) confirms the presence of chloride ions.
- Further reactions with sodium hydroxide (NaOH) lead to the formation of sodium chromate (Na2CrO4), which is yellow in color.

4. **Formation of Lead Chromate**:
- If lead acetate (CH3COO)2Pb is added to the solution, lead chromate (PbCrO4) is formed, which is also yellow in color.
- This can be represented as:
\[ Pb^{2+} + CrO_4^{2-} \rightarrow PbCrO_4 \text{ (yellow precipitate)} \]

5. **Conclusion on Statements**:
- **Statement A**: Formation of chromyl chloride vapor - **Correct**.
- **Statement B**: Liberation of chlorine gas - **Incorrect** (no chlorine gas is liberated during the test).
- **Statement C**: Formation of lead chromate - **Correct**.
- **Statement D**: Formation of reddish-brown vapor - **Correct**.

### Final Answer:
The correct statements regarding the chromyl chloride test are A, C, and D.