In the reaction `: NaCl+ K_(2)Cr_(2)O_(7) +`cons. `H_(2)SO_(4) overset("heat")(rarr)X+ Na_(2)SO_(4) +K_(2)SO_(4)+ H_(2)O , X` is a reddish brown gas which gives a yellow solution on passing through water and a yellow precipitate on treating the solution with lead acetate solution . X could be

Options

A. `Cl_(2)`
B. `CrO_(3)`
C. `H_(2)CrO_(4)`
D. `CrO_(2)Cl_(2)`

Answer

To solve the problem, we need to analyze the reaction given and identify the compound X that is produced. Let's break down the steps:

### Step 1: Identify the Reactants
The reactants in the reaction are:
- Sodium Chloride (NaCl)
- Potassium Dichromate (K₂Cr₂O₇)
- Concentrated Sulfuric Acid (H₂SO₄)

### Step 2: Write the Reaction
When these reactants are heated together, the following reaction occurs:
\[ \text{NaCl} + \text{K}_2\text{Cr}_2\text{O}_7 + \text{H}_2\text{SO}_4 \xrightarrow{\text{heat}} X + \text{Na}_2\text{SO}_4 + \text{K}_2\text{SO}_4 + \text{H}_2\text{O} \]

### Step 3: Identify Compound X
The problem states that X is a reddish-brown gas. This is characteristic of chromyl chloride, which has the chemical formula CrO₂Cl₂.

### Step 4: Properties of Compound X
- When chromyl chloride (CrO₂Cl₂) is passed through water, it forms a yellow solution of sodium chromate (Na₂CrO₄).
- When this yellow solution is treated with lead acetate (Pb(CH₃COO)₂), a yellow precipitate of lead chromate (PbCrO₄) is formed.

### Step 5: Write the Balanced Reaction
The balanced reaction for the formation of chromyl chloride can be written as:
\[ 4 \text{NaCl} + \text{K}_2\text{Cr}_2\text{O}_7 + 3 \text{H}_2\text{SO}_4 \xrightarrow{\text{heat}} 2 \text{CrO}_2\text{Cl}_2 + 2 \text{Na}_2\text{SO}_4 + \text{K}_2\text{SO}_4 + 3 \text{H}_2\text{O} \]

### Conclusion
Thus, the compound X is chromyl chloride (CrO₂Cl₂).

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