Question

Which one of the following is correct statement?

• A. The hydroxide of aluminium is more acidic than that of boron.
• B. They hydroxide of boron is basic, while that of aluminum is amphoteric
• C. The hydroxide of boron is acidic, while that of aluminium is amphoteric
• D. The hydroxide of boron and aluminium are amphoteric

Answer 1

The correct option is C The hydroxide of boron is acidic, while that of aluminium is amphoteric

The hydroxide of boron of acidic, while that of aluminium is amphoteric Boron

and aluminium both are electrophilic in nature due to the presence of an empty p-orbital in case of boron it's empty $2p$ orbital which is small in size and less diffuse which make its overlap with oxygen lone pair more effective which is turn increase the acidity of boron hydroxide but in case of aluminium the $3p$ orbital is involved and is large is longer these properties additively make oxygen lone pair interaction less effective which result into aluminium hydroxides less acidity.