Classify $mathrm{Al}_2 mathrm{O}_3$ and $mathrm{ZnO}$ as amphoteric oxides

Acids, Bases and Salts – Oxides

Amphoteric Oxides: \$Al2O3\$ and \$ZnO\$

Think of an amphoteric oxide like a friendly chameleon 🦎 that can blend in with both acidic and basic environments. It can react with acids to behave like a base, and it can react with bases to behave like an acid.

Exam Tip: Remember that amphoteric oxides appear in both acid and base reactions. Write the balanced equations for each case and check that the products are the expected salts and water.

Reactions with Acids ⚗️

  • \$Al2O3 + 6HCl \;\longrightarrow\; 2AlCl3 + 3H2O\$

  • \$ZnO + 2HCl \;\longrightarrow\; ZnCl2 + H2O\$

Reactions with Bases 🔬

  1. \$Al2O3 + 2NaOH + 3H2O \;\longrightarrow\; 2NaAl(OH)4\$

  2. \$ZnO + NaOH + H2O \;\longrightarrow\; Na2Zn(OH)_4\$

Comparison Table 📊

OxideReaction with AcidReaction with Base
\$Al2O3\$\$2AlCl3 + 3H2O\$\$2NaAl(OH)_4\$
\$ZnO\$\$ZnCl2 + H2O\$\$Na2Zn(OH)4\$

Remember: If an oxide can dissolve in both an acid and a base, it’s amphoteric. Good luck with your studies! 🚀