`(A)+NaCl to (B)` (white ppt.)
`(B)+Kito(C)` (green ppt).
`(C)+underset(("excess"))(KI) to (D)+(E)` (colourless solution)
`(E)+NH_(3)+KOH to (F)`
Q. When compound (A) reacts with `Na_(2)CrO_(4)` solution, the colour of the compound formed is

Options

A. black
B. red
C. yellow
D. white

Explanation

To solve the question step by step, let's analyze the reactions and identify the compounds involved.

### Step 1: Identify Compound A
The question states that compound (A) reacts with NaCl to form a white precipitate (B). The only known compound that fits this description is **Mercurous Nitrate** (Hg2(NO3)2). When it reacts with NaCl, it forms **Mercurous Chloride** (Hg2Cl2), which is a white precipitate.

**Hint:** Look for compounds that form white precipitates when reacting with NaCl.

### Step 2: Identify Compound B
From the previous step, we established that compound (B) is **Hg2Cl2** (Mercurous Chloride).

**Hint:** Remember that the precipitate formed in reactions can help identify the compounds involved.

### Step 3: Identify Compound C
Next, compound (B) reacts with KI to form a green precipitate (C). When Hg2Cl2 reacts with KI, it forms **Mercury(I) Iodide** (Hg2I2), which is a green precipitate.

**Hint:** Focus on the color of the precipitate to help identify the resulting compound.

### Step 4: Identify Compound D and E
The next step involves compound (C) reacting with excess KI. This reaction leads to the formation of two colorless solutions (D and E). The excess KI converts Hg2I2 into **Mercury(I) Iodide** (HgI2) and **Potassium Iodide** (KI).

**Hint:** Excess reagents can lead to the dissolution of precipitates or formation of new compounds.

### Step 5: Identify Compound F
Finally, compound (E) reacts with NH3 and KOH to form compound (F). When HgI2 reacts with NH3 and KOH, it forms **Mercury(I) Ammonium Hydroxide** (which is colorless).

**Hint:** The final step often involves complexation or precipitation reactions that can lead to colorless solutions.

### Final Step: Reaction of Compound A with Na2CrO4
Now, we need to answer the original question: When compound (A) reacts with Na2CrO4, what is the color of the compound formed?

When **Mercurous Nitrate (Hg2(NO3)2)** reacts with **Sodium Chromate (Na2CrO4)**, it forms **Mercury(II) Chromate (Hg2CrO4)**, which is known to be a **red precipitate**.

### Conclusion
The color of the compound formed when compound (A) reacts with Na2CrO4 is **red**.

**Final Answer:** The color of the compound formed is **red**.

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