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Question:

In the following sets of reactants, which two sets exhibit the amphoteric character of Al2O3.xH2O?

2 and 4

1 and 2

1 and 3

3 and 4

Solution:

The correct option is B (1 and 3). Al2O3.xH2O(s) with H+ or OH− exhibit the amphoteric nature. Aluminium oxide is an 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.
Al2O3⋅xH2O + 2NaOH → NaAlO2 + H2O
Al2O3⋅xH2O + HCl → AlCl3 + H2O
Hence, option B is correct.