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Amphoteric Oxides and Hydroxides

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What are Amphoteric Oxides

A substance that reacts with both acids and bases is said to be amphoteric.
Among numerous types, lead oxide and zinc oxide are counted as amphoteric oxides. These metal oxides display amphoteric behaviour by interacting with both acids and bases, resulting in the formation of salts and water. Amphiprotic molecules, falling into the amphoteric category, exhibit the ability to either donate or accept protons (H+), showcasing a dual nature in their reactions.

Amphoteric Properties of Zinc (II) Oxide(ZnO)

When ½ spatula full of Zinc(II)Oxide is placed in a boiling tube containing 10cm3 of either 2M nitric(V)acid or 2M sodium hydroxide solution, it dissolves in both the acid and the alkali/base to form a colourless solution.
When reacting with nitric(V)acid, the oxide shows basic properties by reacting with an acid to form a simple salt and water only.
    ZnO(s) + 2HNO3(aq) → Zn(NO3) 2 (aq) + H2O(l)
    ZnO(s) + 2HCl(aq) → ZnCl2 (aq) + H2O(l)
    ZnO(s) + H2SO4(aq) → ZnSO4 (aq) + H2O(l)
Ionic equation
    ZnO(s) + 2H+ (aq) → Zn2+ (aq) + H2O(l)
When reacting with sodium hydroxide, the oxide shows acidic properties by reacting with a base to form a complex salt.
When Zinc oxide is reacted with sodium hydroxide the complex salt is sodium tetrahydroxozincate(II) complex salt.
    ZnO(s) + 2NaOH(aq) + H2O(l) → Na2Zn(OH)4(aq)
Ionic equation
    ZnO(s) + 2OH-(aq) + H2O(l) → 2[Zn(OH)4]2- (aq)

Amphoteric Properties of Zinc Hydroxide - Zn(OH)2

When Zinc(II)hydroxide is placed in a boiling tube containing 10cm3 of either 2M nitric(V)acid or 2M sodium hydroxide hydroxide solution, it dissolves on both the acid and the alkali/base to form a colourless solution. i.e.
When reacting with nitric(V)acid, the hydroxide shows basic properties. It reacts with an acid to form a simple salt and water only.
    Zn(OH)2 (s) + 2HNO3(aq) → Zn(NO3) 2 (aq) + 2H2O(l)
    Zn(OH)2 (s) + 2HCl(aq) → ZnCl2 (aq) + 2H2O(l)
    Zn(OH)2 (s) + H2SO4(aq) → ZnSO4 (aq) + 2H2O(l)
Ionic equation
    Zn(OH)2 (s) + 2H+ (aq) → Zn2+ (aq) + 2H2O(l)
When reacting with sodium hydroxide, the hydroxide showsacidic properties by reacting with a base to form a complex salt.
When Zinc hydroxide is reacted with sodium hydroxide the complex salt is sodium tetrahydroxozincate (II) complex salt
    Zn(OH)2 (s) + 2NaOH(aq) → Na2Zn(OH)4(aq)
NOTE: Other substances that show similar amphoteric properties include Aluminium(III)oxide(Al2O3) and Aluminium(III)hydroxide(Al(OH)3), Lead (II) Oxide(PbO) and Lead (II) Hydroxide (Pb(OH)2)

Read on:

What are Acids?What are Bases?Acids Reactions with Metal carbonates and Hydrogen CarbonatesPolar and Non-Polar SolventsStrong and Weak Acids and BasesMonobasic, Dibasic, and Tribasic AcidsHygroscopy, Deliquescence and EfflorescencePreparation of Soluble Salts in a LaboratoryCarbonates and Hydrogen Carbonates Reaction with AcidsNeutralization of a Soluble Base with Dilute AcidSalt Preparation by Direct Synthesis or CombinationPreparation of Insoluble SaltsEffect of Heat on Salts

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