Question

In the following sets of reactants which two sets exhibit the amphoteric character of $A{l}_2{O}_3.x{H}_{2}O$?

Set 1 : $A{l}_2{O}_3.x{H}_{2}O$ (s) and $O{H}^{-}\left(aq\right)$
Set 2 : $A{l}_2{O}_3.x{H}_{2}O$ (s) and $H_{2}O\left(l\right)$
Set 3 : $A{l}_2{O}_3.x{H}_{2}O$ (s) and $H^{+}\left(aq\right)$
Set 4 : $A{l}_2{O}_3.x{H}_{2}O$ (s) and $N{H}_3\left(aq\right)$

• A. 1 and 2
• B. 1 and 3
• C. 2 and 4
• D. 3 and 4

Answer 1

Answer: (B)

1 and 3

$A{l}_2{O}_3.x{H}_{2}O$ (s) with $H^{+}$ or $O{H}^{-}$ exhibit the amphoteric nature. Aluminium oxide is amphoteric oxide because it shows the properties of both acidic and basic oxides. It reacts with both acids and bases to form salt and water.

$A{l}_2{O}_3\cdot x{H}_{2}O+2NaOH⟶NaAl{O}_2+H_{2}O$

$A{l}_2{O}_3\cdot x{H}_{2}O+HCl⟶AlC{l}_3+H_{2}O$

Hence, option B is correct.