An aqueous solution contain either `Hg_2^(2+) " or " Hg^(2+)` the given solution given green ppt with `KI` solution . About the given aqueous solution which of the following is incorrect ?

Options

A. It contain `Hg_2^(2+)`
B. It contain `Hg^(2+)`
C. with `NH_3` solution it gives black precipitate
D. With NaCl solution it gives white precipitate

Answer

To solve the problem, we need to analyze the behavior of the two mercury ions, \( \text{Hg}_2^{2+} \) and \( \text{Hg}^{2+} \), in the presence of potassium iodide (KI) and other reagents mentioned in the options.

### Step-by-Step Solution:

1. **Identify the Reaction with KI:**
- When an aqueous solution containing either \( \text{Hg}_2^{2+} \) or \( \text{Hg}^{2+} \) is treated with KI, a green precipitate is formed. This green precipitate is identified as \( \text{Hg}_2I_2 \).

2. **Determine the Ion Present:**
- The formation of \( \text{Hg}_2I_2 \) indicates that the solution contains \( \text{Hg}_2^{2+} \) ions. This is because \( \text{Hg}^{2+} \) would typically form a different precipitate (like \( \text{HgI}_2 \)).

3. **Evaluate Each Option:**
- **Option A:** "It contains \( \text{Hg}_2^{2+} \)" - This is correct since the green precipitate indicates the presence of \( \text{Hg}_2^{2+} \).
- **Option B:** "It contains \( \text{Hg}^{2+} \)" - This is incorrect because the green precipitate formation indicates that \( \text{Hg}^{2+} \) is not present.
- **Option C:** "It reacts with ammonia to give a black precipitate" - This is correct. \( \text{Hg}_2^{2+} \) reacts with ammonia to form metallic mercury (Hg) which is black.
- **Option D:** "With NaCl solution gives a white precipitate" - This is also correct. \( \text{Hg}_2^{2+} \) reacts with NaCl to form \( \text{Hg}_2Cl_2 \), which is white.

4. **Conclusion:**
- The only incorrect statement is Option B, which claims the solution contains \( \text{Hg}^{2+} \).

### Final Answer:
The incorrect statement about the given aqueous solution is **Option B**.