In the following sets of reactants which two sets best exhibit the amphoteric characters of $\mathrm{Al}_{2}…

In the following sets of reactants which two sets best exhibit the amphoteric characters of
$\mathrm{Al}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O} ?$
Set 1: $\mathrm{Al}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{s})$ and $\mathrm{OH}^{-}($ aq $)$
Set 2: $\mathrm{Al}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{s})$ and $\mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
Set 3: $\mathrm{Al}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{s})$ and $\mathrm{H}^{+}(\mathrm{aq})$
Set 4: $\mathrm{Al}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{s})$ and $\mathrm{NH}_{3}(\mathrm{aq})$
  1. 1 and 2
  2. 1 and 3
  3. 2 and 4
  4. 3 and 4

Solution

Aluminium oxide is amphoteric oxide because it shows the properties of the both acidic and basic oxides. It reacts with both acids and bases to form salt and water.
$\mathrm{Al}_{2} \mathrm{O}_{3} \cdot x \mathrm{H}_{2} \mathrm{O}+2 \mathrm{NaOH} \longrightarrow \mathrm{NaAlO}_{2}+\mathrm{H}_{2} \mathrm{O}$
$\mathrm{Al}_{2} \mathrm{O}_{3} \cdot x \mathrm{H}_{2} \mathrm{O}+\mathrm{HCl} \longrightarrow \mathrm{AlCl}_{3}+\mathrm{H}_{2} \mathrm{O}$

Asked in: JEE-TOPICTESTS-CHEMISTRY

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