Compound X on reduction with `LiAlH_(4)` gives a hydride Y containing 21.72% hydrogen and other products. The compound Y reacts with air expolosively resulting in boron trioxide. What are X and Y respectively ?

Options

A. `BCl_(3), B_(2)H_(6)`
B. `PCl_(3), B_(2)H_(6)`
C. `B_(2)H_(6), BCl_(3)`
D. `LiAlH_(4),PCl_(3)`

Explanation

To solve the problem, we need to identify the compounds X and Y based on the given information.

### Step-by-Step Solution:

1. **Understanding the Reduction Reaction**:
- Compound X is reduced by lithium aluminum hydride (LiAlH4) to form compound Y.
- The reduction process typically involves the addition of hydrogen or the removal of oxygen.

2. **Analyzing Compound Y**:
- Compound Y contains 21.72% hydrogen. To find its molecular formula, we can use the percentage composition.
- The remaining percentage (100% - 21.72%) is attributed to other elements, which in this case would be boron (B).

3. **Calculating the Empirical Formula**:
- Let's assume we have 100 g of compound Y. This means we have 21.72 g of hydrogen and 78.28 g of boron.
- The molar mass of hydrogen (H) is approximately 1 g/mol, and for boron (B), it is approximately 10.81 g/mol.
- Moles of hydrogen = 21.72 g / 1 g/mol = 21.72 mol
- Moles of boron = 78.28 g / 10.81 g/mol ≈ 7.25 mol

4. **Finding the Ratio**:
- The ratio of moles of boron to moles of hydrogen is approximately 7.25:21.72, which simplifies to about 1:3.
- This suggests that the empirical formula of compound Y is B2H6 (diborane), which is consistent with the explosive reaction with air.

5. **Identifying Compound X**:
- Given that Y is B2H6, we need to find a compound X that can produce B2H6 upon reduction with LiAlH4.
- BCl3 (boron trichloride) is known to react with LiAlH4 to produce diborane (B2H6) and other by-products.
- The balanced reaction is:
\[ 2 BCl_3 + 6 LiAlH_4 \rightarrow B_2H_6 + 6 LiCl + 3 AlCl_3 \]

6. **Conclusion**:
- Therefore, compound X is BCl3 and compound Y is B2H6.

### Final Answer:
- X = BCl3 (Boron Trichloride)
- Y = B2H6 (Diborane)