Acid Oxides, Basic Oxides and Acid Anhydrides
Oxides can be both metallic and non metallic. These oxides can further described as acidic, basic, neutral and amphoteric oxides.
Acidic Oxides (non metallic)
Acidic oxides are oxides of non-metals that neutralize bases to form salt and water only, example:
CO2 (g)+ 2 NaOH (aq) → Na2CO3(s) + H2O (l)
An acidic anhydride is an acidic oxide which dissolves in water to form an acid solution.
CO2 (g) + H2O (l)→ H2CO3 (aq) carbonic acid
SO3 (g) + H2O (l) → H2SO4 (aq) sulphuric acid
NO2 is a mixed acid anhydride because it dissolves in water to produce 2 acids:
2NO2 (g) + H2O (l) → HNO3 (aq) + HNO2 (aq) nitric acid
These are oxides of metal which neutralize acids to form salt and water only. For example the basic oxide MgO (magnesium oxide) neutralises Sulphuric acid to form magnesium sulphate (salt) and water.
MgO (s) + H2SO4 (aq) → MgSO4 (aq) + H2O (l)
Basic oxides can be either soluble or insoluble. Soluble oxides dissolve in water to form alkaline solutions.
These are oxides of non-metal that neither neutralizes acids or base, example CO, NO and H2O
These are oxides of metals that neutralize both acid and bases to form a salt and water
Examples: Al2O3, ZnO
ZnO(s) + H2SO4 (aq) → ZnSO4 (aq) + H2O
ZnO + NaOH + H2O → Na2 (Zn (OH) 4)
Na2 (Zn (OH) 4) – This is a complex ion. You will be introduced to this later in your studies in chemistry. For now, appreciate the fact that ZnO is an amphoteric oxide which neutralizes both acidic and alkaline solutions.