Reactions of Acids

• An acid is a solution with a pH less than 7.
• A neutral solution has a pH of 7.
• An acid is a substance that releases H+ ions when dissolved in water.
• pH is measured using universal indicator or a pH probe.
• A strong acid completely ionises in water whereas a weak acid only partially ionises.
• A salt is a compound formed when a metal ion takes the place of a hydrogen ion in an acid.
• Sulfuric acids form sulfates.

  Hydrochloric acid forms chlorides.

  Nitric acid forms nitrates.
• Metal + Acid -> Salt + Hydrogen

  Metal Hydroxide + Acid -> Salt + Water

  Metal Oxide + Acid -> Salt + Water

  Metal Carbonate + Acid -> Salt + Water + Carbon Dioxide
• A base is a substance that reacts with acids in neutralisation reactions.
• An alkali is a substance that dissolves in water to form a solution above pH 7.
• A neutralisation reaction is a reaction between an acid and a base to produce water.
• Ionic equation for neutralisation:

  H+ (aq) + OH- (aq) -> H2O (l)
• Crystallisation is used to obtain a solid salt from a solution.
• When an acid reacts with a metal, the metal is oxidised.
• When an acid reacts with a metal, hydrogen is reduced.