What are amphoteric oxides? Give two examples. Write balanced chemical equations showing the reaction of aluminium oxide

Question

What are amphoteric oxides? Give two examples. Write balanced chemical equations showing the reaction of aluminium oxide ($Al2O3$) with both hydrochloric acid ($HCl$) and sodium hydroxide ($NaOH$).

Accepted Answer

Metal oxides that react with both acids as well as bases to produce salt and water are known as amphoteric oxides. These oxides display both acidic and basic behaviors depending on the reacting substance. Two common examples of amphoteric oxides are aluminium oxide ($Al2O3$) and zinc oxide ($ZnO$). When aluminium oxide reacts with hydrochloric acid (an acid), it acts as a basic oxide and produces aluminium chloride and water: $$Al2O3(s) + 6HCl(aq) \rightarrow 2AlCl3(aq) + 3H2O(l)$$ When aluminium oxide reacts with sodium hydroxide (a strong base), it acts as an acidic oxide and forms sodium aluminate and water: $$Al2O3(s) + 2NaOH(aq) \rightarrow 2NaAlO2(aq) + H2O(l)$$ Thus, aluminium oxide clearly exhibits dual chemical nature, confirming its amphoteric character.

Metals and Non-metals

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