`Mg_(3)B_(2) overset(aq. HCl)(rarr) underset(y+H_2)underset(darrH_2O)x + MgCl_2`
for (X) and (Y) the incorrect choice is?

Options

A. `(X)` is `BCl_3`
B. `(Y)` is `H_2BO_3`
C. (X) with air and (Y) on strong heating (red heat) give same compound
D. In (Y) boron completes is octet by moving `H^(+)` from water molecule

Answer

To solve the given question, we need to analyze the reaction of magnesium diboride (Mg₃B₂) with hydrochloric acid (HCl) and determine the products formed, specifically identifying the compounds represented by (X) and (Y).

### Step-by-Step Solution:

1. **Identify the Reactants:**
The reactants are magnesium diboride (Mg₃B₂) and hydrochloric acid (HCl).

2. **Write the Balanced Reaction:**
When Mg₃B₂ reacts with HCl, it produces magnesium chloride (MgCl₂) and other products. The reaction can be represented as:
\[ \text{Mg}_3\text{B}_2 + \text{HCl} \rightarrow \text{X} + \text{MgCl}_2 + \text{Y} + \text{H}_2 \]

3. **Determine the Products:**
- **(X)**: The product formed from the reaction of diboride with HCl is diborane (B₂H₆).
- **(Y)**: The product formed when diborane reacts with water (H₂O) is boric acid (H₃BO₃).

4. **Identify the Incorrect Choice:**
We need to check the options provided for (X) and (Y) to find the incorrect one.
- If (X) is stated as BCl₃, that is incorrect because (X) should be B₂H₆.
- If (Y) is stated as H₂BO₃, that is also incorrect because (Y) should be H₃BO₃.

5. **Conclusion:**
The incorrect choices for (X) and (Y) are:
- (X) = BCl₃ (incorrect, should be B₂H₆)
- (Y) = H₂BO₃ (incorrect, should be H₃BO₃)

### Final Answer:
The incorrect choice is (X) = BCl₃ and (Y) = H₂BO₃.