Neutralisation (unit 1)

• Bases are substances that can neutralise acids to form water.
• Bases: ALKALIS – e.g. NaOH, all contain hydroxide ions

  METAL OXIDES – e.g. CaO, all contain the oxide ion

  METAL CARBONATES – e.g. CaCO3, all contain the carbonate ion
• When a base dissolves in water an alkali is formed.
• A neutralisation reaction is the reaction of acids with bases.
• Neutralisation moves the pH of an acid up towards 7. Neutralisation moves the pH of an alkali down

  towards 7.
• ACID + ALKALI = SALT + WATER

  ACID + METAL OXIDE = SALT + WATER

  ACID + METAL CARBONATE = SALT + WATER + CARBON DIOXIDE
• The ions which do not change in an equation are called spectator ions (they simply watch the reaction).
• Examples of Neutralisation:

  Acids are often neutralised in everyday chemical reactions.

  Some examples of these are:

  • Indigestion (antacid) tablets are used to neutralise excess stomach acid
  • Lime (calcium oxide) is used to reduce the acidity of soil and lakes/lochs (caused by acid rain)
• An accurate way to determine the concentration of an acid or alkali, in a neutralisation reaction, is to use a titration.
• The volumes of acid and alkali can be accurately measured using a pipette and burette.