Question

What is the nature of $A{l}_2{O}_{3}and{B}_2{O}_3$

• A. Amphoteric, acidic
• B. Acidic amphoteric
• C. Acidic, Acidic
• D. Amphoteric amphoteric

Answer 1

The correct option is A Amphoteric, acidic

As Electronegativity decreases down the group, so, does acidic strength.

But $A{l}_2{O}_3$ reacts with both $O{H}^{-}$ and $H_3{O}^{+}$ to form $\left[Al\right(OH{)}_4{]}^{-}$ and $\left[Al\right(H_{2}O{)}_6{]}^{3+}$ because $A{l}^{3+}$ ion is larger and softer.

While, In $B_2{O}_3$, the small, hard $B^{3+}$ holds on the oxide ions strongly. As a result

$B_2{O}_3+3H_{2}O\to 2B(OH{)}_3\leftrightarrow H^{+}+H_{2}B{O}_3^{-}$

And the solution is very weakly acidic.