Question

In which of the following reactions, hydrogen is one of the products?

• A. \[ \text{NaBH}_4 + \text{I}_2 \rightarrow \]
• B. \[ \text{BF}_3 + \text{NaH} \xrightarrow{450\,K} \]
• C. \[ \text{BF}_3 + \text{LiAlH}_4 \rightarrow \]
• D. \[ \text{B}_2\text{H}_6 + \text{NH}_3 \xrightarrow{\text{heat}} \]

Hint:

Whenever analyzing chemical reactions for gas evolution, check for common gas-producing reactants like metal hydrides, acids, or decomposition reactions.

Answer 1

The Correct Option is C

We need to determine in which of the given reactions hydrogen (\( H_2 \)) is produced as a product. 

Step 1: Analyze each reaction 
1. Reaction i: \( \text{NaBH}_4 + I_2 \) Sodium borohydride reacts with iodine to release molecular hydrogen (\( H_2 \)) as one of the products: \[ \text{NaBH}_4 + 2I_2 \rightarrow \text{NaI} + \text{BI}_3 + H_2 \] Thus, hydrogen is produced in this reaction. 2. Reaction ii: \( \text{BF}_3 + \text{NaH} \) This reaction does not produce hydrogen. Instead, it forms sodium tetrafluoroborate. 3. Reaction iii: \( \text{BF}_3 + \text{LiAlH}_4 \) This reaction is a reduction process and does not yield hydrogen as a product. 4. Reaction iv: \( \text{B}_2\text{H}_6 + \text{NH}_3 \) Diborane reacts with ammonia to form boron nitride and molecular hydrogen: \[ \text{B}_2\text{H}_6 + 2\text{NH}_3 \rightarrow 2\text{BN} + 3H_2 \] Thus, hydrogen is produced in this reaction. 

Step 2: Identifying the correct answer 
From the above analysis, hydrogen is produced in reactions (i) and (iv). Thus, the correct answer is:\((C) i, iv\)