Question

In which of the following reactions, hydrogen is one of the products formed?
Reaction of BF\(_3\) with LiAlH\(_4\) in diethyl ether Hydrolysis of diborane Oxidation of sodium borohydride with iodine Combustion of diborane

• A. ii, iv only
• B. ii, iii only
• C. i, iii only
• D. i, iv only

Hint:

Remember the reactions of boron compounds, especially diborane and sodium borohydride.

Answer 1

The Correct Option is B

1. Reaction of BF\(_3\) with LiAlH\(_4\) in diethyl ether: BF\(_3\) + LiAlH\(_4\) \(\rightarrow\) B\(_2\)H\(_6\) + LiF + AlF\(_3\) Products: Diborane (B\(_2\)H\(_6\)), Lithium fluoride (LiF), Aluminum fluoride (AlF\(_3\)) No hydrogen (H\(_2\)) is formed. 
2. Hydrolysis of diborane: B\(_2\)H\(_6\) + 6H\(_2\)O \(\rightarrow\) 2B(OH)\(_3\) + 6H\(_2\) Products: Boric acid (B(OH)\(_3\)), Hydrogen (H\(_2\)) 3. Oxidation of sodium borohydride with iodine: 2NaBH\(_4\) + I\(_2\) \(\rightarrow\) 2NaI + B\(_2\)H\(_6\) + H\(_2\) Products: Sodium iodide (NaI), Diborane (B\(_2\)H\(_6\)), Hydrogen (H\(_2\)) 
4. Combustion of diborane: B\(_2\)H\(_6\) + 3O\(_2\) \(\rightarrow\) B\(_2\)O\(_3\) + 3H\(_2\)O Products: Boron trioxide (B\(_2\)O\(_3\)), Water (H\(_2\)O) No hydrogen (H\(_2\)) is formed. Therefore, hydrogen is formed in reactions (ii) and (iii). 
Final Answer: ii, iii only.