(a) Classify following oxides as neutral, acidic, basic or amphoteric:

CO, B2O3, SiO2, CO2, Al2O3, PbO2, Tl2O3


(b) Write suitable chemical equations to show their nature.

SiO2= Acidic

Being acidic, it reacts with bases to form salts. It reacts with NaOH to form sodium silicate.


SiO2 + 2NaOH → 2Na2SiO3 + H2O


→ Tl2O3 = Basic


Being basic, it reacts with acids to form salts. It reacts with HCl to form thallium chloride.


Tl2O3 + 6HCl → 2TlCl3 + 3H2O


→ CO = Neutral


→ CO2 = Acidic


Being acidic, it reacts with bases to form salts. It reacts with NaOH to form sodium carbonate.


CO2 + 2NaOH → Na2CO3 + H2O


→ B2O3 = Acidic


Being acidic, it reacts with bases to form salts. It reacts with NaOH to form sodium metaborate.


B2O3 + 2NaOH → 2NaBO2 + H2O


→ PbO2 = Amphoteric


Amphoteric substances react with both acids and bases. PbO2 reacts with both NaOH and H2SO4.


PbO2 + 2NaOH → Na2PbO3 + H2O


2PbO2 + 2H2SO4→ 2PbSO4 + 2H2O + O2


→ Al2O3= Amphoteric


Amphoteric substances react with both acids and bases. Al2O3 reacts with both NaOH and H2SO4.


Al2O3 + 2NaOH → NaAlO2


Al2O3 + 3H2SO4→ Al2(SO4)3 + 3H2O


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