Compound `(X)` on reduction with `LiAlH_(4)` gives a hydride `(Y)` containing `21.72 %` hydrogen along with other products. The compound `(Y)` reacts with air explosively resulting in formation of boron trioxide. Identify `(X)` and `(Y)`.
Give balanced reactions involved in the formation of `(Y)` and its reaction with air. Give the structure of `(Y)`.

Options

A. `BCl_(2), B_(2)H_(6)`
B. `B_(2)H_(6), BCl_(3)`
C. `BF_(3),Al_(2)O_(6)`
D. `B_(2)H_(6),BF_(3)`

Answer

To solve the problem, we need to identify the compounds (X) and (Y) based on the information provided. Let's break down the steps:

### Step 1: Identify Compound (X)
The problem states that compound (X) on reduction with LiAlH4 gives a hydride (Y) containing 21.72% hydrogen. The only boron compound that fits this description is boron trihalide (BX3), where X can be a halogen (like Cl, Br, or I).

### Step 2: Determine the Formula for (Y)
When BX3 is reduced with LiAlH4, it forms diborane (B2H6) as the hydride (Y). This is a common reaction for boron compounds.

### Step 3: Calculate the Percentage of Hydrogen in (Y)
To confirm that B2H6 contains 21.72% hydrogen, we can calculate the percentage of hydrogen in B2H6:
- The molar mass of B2H6 = (2 × 10.81) + (6 × 1.008) = 21.62 + 6.048 = 27.668 g/mol.
- The mass of hydrogen in B2H6 = 6.048 g.
- Percentage of hydrogen = (mass of H / molar mass of B2H6) × 100 = (6.048 / 27.668) × 100 ≈ 21.85%.

This is close enough to the given percentage (21.72%), confirming that (Y) is indeed B2H6.

### Step 4: Write the Balanced Reaction for the Formation of (Y)
The balanced reaction for the reduction of BX3 with LiAlH4 is:
\[ 4BX_3 + 3LiAlH_4 \rightarrow 2B_2H_6 + 3LiX + 3AlX_3 \]

### Step 5: Write the Reaction of (Y) with Air
Diborane (B2H6) reacts with oxygen (air) explosively to form boron trioxide (B2O3) and water (H2O). The balanced reaction is:
\[ 2B_2H_6 + 7O_2 \rightarrow 4B_2O_3 + 6H_2O \]

### Step 6: Identify the Structure of (Y)
The structure of diborane (B2H6) can be represented as follows:
```
H H
\ /
B - B
/ \
H H
```
In this structure, the two boron atoms are connected, and each boron atom is bonded to three hydrogen atoms, with two of the hydrogen atoms forming bridge bonds between the boron atoms.

### Final Answer
- Compound (X) is BX3 (boron trihalide).
- Compound (Y) is B2H6 (diborane).
- Balanced reactions:
1. Formation of (Y):
\[ 4BX_3 + 3LiAlH_4 \rightarrow 2B_2H_6 + 3LiX + 3AlX_3 \]
2. Reaction of (Y) with air:
\[ 2B_2H_6 + 7O_2 \rightarrow 4B_2O_3 + 6H_2O \]