Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with `H_2O_2` due to the formation of (P)
The yellow solution (X) is

Options

A. `K_2CrO_4`
B. `Na_2CrO_4`
C. `CrCl_3`
D. `Cr(OH)_3`

Explanation

To find the yellow solution (X) formed when potassium dichromate is heated with metal chloride and concentrated sulfuric acid, and then passed through sodium hydroxide, we can follow these steps:

### Step 1: Understand the Reaction of Potassium Dichromate
Potassium dichromate (K2Cr2O7) acts as a strong oxidizing agent, especially in acidic medium. When it is heated with a metal chloride (like NaCl) and concentrated sulfuric acid (H2SO4), it produces chromyl chloride (CrO2Cl2) along with other products.

**Hint:** Remember that potassium dichromate is a strong oxidizer and can react with chlorides to form chromyl chloride.

### Step 2: Identify the Products of the Reaction
The reaction can be summarized as:
\[ \text{K}_2\text{Cr}_2\text{O}_7 + \text{NaCl} + \text{H}_2\text{SO}_4 \rightarrow \text{CrO}_2\text{Cl}_2 + \text{NaHSO}_4 + \text{KHSO}_4 + \text{H}_2\text{O} \]
Here, chromyl chloride (CrO2Cl2) is the key product that gives off orange-red fumes.

**Hint:** Focus on the formation of chromyl chloride as it is essential for the next step.

### Step 3: Passing Fumes Through Sodium Hydroxide
When the orange-red fumes (chromyl chloride) are passed through sodium hydroxide (NaOH), a reaction occurs that results in the formation of sodium chromate (Na2CrO4), which is a yellow solution.

**Chemical Reaction:**
\[ \text{CrO}_2\text{Cl}_2 + 4 \text{NaOH} \rightarrow \text{Na}_2\text{CrO}_4 + 2 \text{NaCl} + 2 \text{H}_2\text{O} \]

Thus, the yellow solution (X) formed is sodium chromate (Na2CrO4).

**Hint:** Remember that sodium chromate is known for its yellow color, which is a key indicator in this reaction.

### Step 4: Conclusion
The yellow solution (X) is identified as sodium chromate (Na2CrO4).

### Summary of the Solution:
- Potassium dichromate reacts with metal chloride and concentrated sulfuric acid to form chromyl chloride, which gives orange-red fumes.
- Passing these fumes through sodium hydroxide yields sodium chromate, resulting in a yellow solution (X).
- Therefore, the yellow solution (X) is **sodium chromate (Na2CrO4)**.