1. Topic 9
Reactions of
Acids

2. Acids and Metal Oxides
Farmers often use lime to reduce the acidity of their soil. Lime is a metal oxide- calcium oxide.
Metal oxides will neutralise acids to form a salt and water.
Metal oxide + Acid  Salt + Water
Magnesium oxide + Carbonic Acid  Magnesium carbonate + water
MgO + H2CO3  MgCO3 + H2O

3. The other ions present are spectator ions.
Copper (II) oxide + sulphuric acid  Copper sulphate + Water
CuO + H2SO4  CuSO H2O
In this reaction the H+ ions from the acids are reacting with the O2- ions from the metal oxide to form water:
2H O  H2O
The other ions present are spectator ions.

4. Preparation of these Salts
An insoluble metal oxide is used
e.g. copper (II) oxide
2. Excess metal oxide is added to
the acid e.g. sulphuric acid and
warmed gently.
3. When the reaction is complete,
excess metal oxide can be
removed by filtration.

5. 4. The solution (filtrate) is
evaporated to dryness to
obtain a solid sample of the
product.
Everyday example: Farmers often use lime to reduce the acidity of their soil. Lime is a metal oxide- calcium oxide.

6. Bases A base is a substance which neutralises an acid.
Examples of bases: alkalis (metal hydroxides), metal oxides and metal carbonates are all examples of bases.
An alkali is made if the base dissolves in water. The data book shows which bases dissolve in water. Examples: carbonates and hydroxides of Group 1 elements, of some Group 2 elements, and ammonium compounds.
Metals do not dissolve in water.

7. Metal Compounds
Bases
Alkalis

8. Preparation of Compounds by Neutralisation and Evaporation
N.B.
This method is easier than using soluble neutralisers (titration or pH paper) because:
Unreacted neutraliser can be removed easily (filtration)
End-point not over-shot (think about the first experiment with acids and alkalis)