Which of the following statement (s) is (are) correct when a mixture of NaCl and `K_(2)Cr_(2)O_(7)` is gently warmed with conc. `H_(2)SO_(4)` ?

Options

A. A deep red vapour is evolved
B. The vapour when passed into NaOH solution gives a yellow solution of `Na_(2)CrO_(4)`
C. Chlorine gas is evolved
D. Chromyl chloride is formed

Answer

To solve the question regarding the reaction of a mixture of NaCl and K2Cr2O7 when gently warmed with concentrated H2SO4, we will analyze the chemical processes involved step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reactants in this scenario are sodium chloride (NaCl) and potassium dichromate (K2Cr2O7).

2. **Understand the Reaction with Concentrated H2SO4**:
When NaCl and K2Cr2O7 are mixed and gently warmed with concentrated sulfuric acid (H2SO4), a series of reactions occur. The concentrated sulfuric acid acts as a dehydrating agent and facilitates the formation of chromyl chloride (CrO2Cl2) and other products.

3. **Write the Balanced Chemical Equation**:
The balanced equation for the reaction is:
\[ 4 NaCl + K2Cr2O7 + 6 H2SO4 \rightarrow 2 CrO2Cl2 + 4 NaHSO4 + 2 KHSO4 + 3 H2O \]
This equation shows that chromyl chloride (CrO2Cl2) is formed, which is responsible for the deep red vapor observed during the reaction.

4. **Observations from the Reaction**:
- **Deep Red Vapor**: The formation of CrO2Cl2 results in the evolution of deep red vapors.
- **Passing Vapor into NaOH**: When the red vapor (CrO2Cl2) is passed into a sodium hydroxide (NaOH) solution, it reacts to form sodium chromate (Na2CrO4), which is yellow in color:
\[ CrO2Cl2 + 4 NaOH \rightarrow Na2CrO4 + 2 NaCl + 2 H2O \]
- **Chlorine Gas**: Chlorine gas is not evolved in this reaction. The reaction primarily produces chromyl chloride and sodium bisulfate, not chlorine gas.
- **Formation of Chromyl Chloride**: As established, chromyl chloride (CrO2Cl2) is indeed formed during the reaction.

5. **Conclusion**:
Based on the analysis:
- Statement A: A deep red vapor is evolved - **True**
- Statement B: The vapor when passed into NaOH solution gives a yellow solution of Na2CrO4 - **True**
- Statement C: Chlorine gas is evolved - **False**
- Statement D: Chromyl chloride is formed - **True**

### Final Answer:
The correct statements are A, B, and D.