`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_3BO_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 question regarding the reaction of \( \text{Mg}_3\text{B}_2 \) with aqueous HCl and the subsequent reactions, we will follow these steps:

### Step 1: Identify the Reaction of \( \text{Mg}_3\text{B}_2 \) with Aqueous HCl

The first step is to write the balanced chemical equation for the reaction of magnesium diboride (\( \text{Mg}_3\text{B}_2 \)) with hydrochloric acid (\( \text{HCl} \)). The products of this reaction are diborane (\( \text{B}_2\text{H}_6 \)) and magnesium chloride (\( \text{MgCl}_2 \)).

The balanced equation is:
\[ \text{Mg}_3\text{B}_2 + 6 \text{HCl} \rightarrow \text{B}_2\text{H}_6 + 3 \text{MgCl}_2 \]

### Step 2: Identify Product X

From the balanced equation, we can see that product \( X \) is diborane (\( \text{B}_2\text{H}_6 \)).

### Step 3: Reaction of X with Water

Next, we need to determine what happens when \( X \) (diborane) reacts with water. The reaction of diborane with water produces boric acid (\( \text{H}_3\text{BO}_3 \)) and hydrogen gas (\( \text{H}_2 \)).

The balanced equation for this reaction is:
\[ \text{B}_2\text{H}_6 + 6 \text{H}_2\text{O} \rightarrow 2 \text{H}_3\text{BO}_3 + 3 \text{H}_2 \]

### Step 4: Identify Product Y

From this reaction, we can conclude that product \( Y \) is boric acid (\( \text{H}_3\text{BO}_3 \)).

### Step 5: Evaluate the Given Options

Now, we need to evaluate the given options to identify which one is incorrect regarding \( X \) and \( Y \).

1. **Option A**: \( X \) is \( \text{BCl}_3 \) - **Incorrect** (since \( X \) is \( \text{B}_2\text{H}_6 \)).
2. **Option B**: \( Y \) is \( \text{H}_3\text{BO}_3 \) - **Correct** (since \( Y \) is indeed boric acid).
3. **Option C**: \( X \) with air and \( Y \) on strong heating gives the same compound - **Correct** (both yield \( \text{B}_2\text{O}_3 \)).
4. **Option D**: In \( Y \), boron completes its octet by moving \( H^+ \) from the water molecule - **Correct** (this describes the reaction mechanism accurately).

### Conclusion

Thus, the incorrect choice regarding products \( X \) and \( Y \) is **Option A**.

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