Which one of the following is correct st...

Which one of the following is correct statement?

The hydroxide of aluminium is more acidic than that of boron

The hydroxide of boron is basic, while that of aluminium is amphoteric

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

The hydroxides of boron and aluminium are amphoteric

Text Solution

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The correct Answer is:

Boric acid is a hydroxide of boron, which is soluble in water and behaves as a weak monobasic acid. It does not donate proton like most acids. But rather it accepts `OH^(-)` ions. It is therefore, a Lewis acid `B(OH)_3 +2H_2O harr 2H_3O^(+) +[B(OH)_4]^(-)`
Hydroxide of aluminium `[Al(OH)_3]` is amphoteric. It reacts principally as a base, that is, it reacts with acids to form salts that contain the `[Al(H_2O)_6]^(3+)` ion. However, `Al(OH)_3` shows some acidic properties when it is dissolved in NaOH forming sodium aluminate.

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