Question

Choose the wrong statement in the following with regard to orthoboric acid:

• A. It can be prepared by the hydrolysis of boron trihalide
• B. It is freely soluble in cold water
• C. It has a layer structure
• D. It is not a protonic acid but acts as a Lewis acid
• E. On heating above 370K it forms first metaboric acid which on further heating yields $B_2O_3$

Answer 1

The Correct Option is B

Let's evaluate each statement about orthoboric acid (H₃BO₃): 

• It can be prepared by the hydrolysis of boron trihalide: This statement is correct. Orthoboric acid can be prepared by hydrolyzing boron trihalide (such as BCl₃) in water.
• It is not a protonic acid but acts as a Lewis acid: This statement is correct. While orthoboric acid doesn't behave as a typical protonic acid, it acts as a Lewis acid by accepting electron pairs.
• It has a layer structure: This statement is correct. Orthoboric acid has a layered structure in its solid state, where each boron atom is connected to three hydroxyl groups.
• It is freely soluble in cold water: This statement is incorrect. Orthoboric acid is only sparingly soluble in cold water, not freely soluble.
• On heating above 370K it forms first metaboric acid which on further heating yields B₂O₃: This statement is correct. Orthoboric acid undergoes dehydration upon heating to form metaboric acid, which can further dehydrate to form boron oxide (B₂O₃).

Correct Answer: (B) It is freely soluble in cold water