2 Acids and Metal OxidesFarmers 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 + WaterMagnesium oxide + Carbonic Acid Magnesium carbonate + waterMgO + H2CO3 MgCO3 + H2O
3 The other ions present are spectator ions. Copper (II) oxide + sulphuric acid Copper sulphate + WaterCuO + H2SO4 CuSO H2OIn this reaction the H+ ions from the acids are reacting with the O2- ions from the metal oxide to form water:2H O H2OThe other ions present are spectator ions.
4 Preparation of these Salts An insoluble metal oxide is usede.g. copper (II) oxide2. Excess metal oxide is added tothe acid e.g. sulphuric acid andwarmed gently.3. When the reaction is complete,excess metal oxide can beremoved by filtration.
5 4. The solution (filtrate) is evaporated to dryness toobtain a solid sample of theproduct.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.
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)