Acids and Alkalis

Testing the pH of a solution means using an indictor
The pH scale goes from 0 to 14
1. The pH scale is a measure of how acidic or alkaline a solution is
  1. The strongest acid has pH 0
  2. The strongest alkali has pH 14
  3. A neutral substance has pH 7
An indicator is just a dye that changes colour
1. The dye changes colour depending on whether its above or below a certain pH
  1. Useful for estimating the pH of a solution
Acids and Bases neutralise each other
1. An acid is a substance with a pH of less than 7. Acids form H+ ions in water
  1. H+ is hydrogen
2. A base is a substance with a pH of greater than 7
  1. An alkali is a base that dissolves in water. Alkalis form OH- ions in water.
    1. OH- is hydroxide
3. The reaction between acids and bases is called neutralisation
  1. acid + base to salt + water
    1. H + (aq) + OH- (aq) to H2O (l)
4. State symbols tell you what physical state its in
  1. (s) is solid, (l) is liquid, (g) is gas, (aq) is dissolved in watter
Acids Reacting with metals
1. Metals react with acids to give salts
  1. Acid + Metal to Salt + Hydrogen
2. The more reactive the metal the faster the reaction will go very reactive metals react explosively
3. Copper does not react with dilute acids at all because its less reactive than hydrogen
  1. The speed of reaction is indicated by the rate at which the bubbles of hydrogen are given off
  2. The hydrogen is confirmed by the burning splint test giving the notorious squeaky pop
  3. The name of the salt produced depends on which metal is used and which acid is used
    1. Hydrochloric acid will always produce chloride salts
      1. 2HCl + Mg to MgCl2 + H2 (magnesium chloride)
        6HCl + 2Al to 2AlCl3 +3H2 (aluminium chloride)
        2HCl + Zn to ZnCl2 + H2
    2. Sulfuric acid will always produce sulfate salts
      1. H2SO4 + Mg to MgSO4 + H2 ( magnesium chloride)
        3H2SO4 + 2Al to Al2(SO4)3 + 3H2 (aluminium sulfate)
        H2SO4 + Zn to ZnSO4 + H2 (Zinc sulfate)
    3. Nitric acid produces nitrate salts when neutralised
      1. Nitric acid reacts with fine with alkalis to produce nitrates but when reacted with metals and produce nitrogen oxides instead
Oxides, Hydroxides and Ammonia
1. Metal oxides and metal hydroxides are bases
  1. Some metal oxides and metal hydroxides dissolve in water. These soluble compounds are alkali
  2. even bases that wont dissolve in water will still react with acids
  3. Acid + Metal oxide to salt + water
  4. Acid + Metal hydroxide to salt + water
2. The combination of metal and acid decides the salt
  1. hydrochloric acid + copper oxide to copper chloride + water
    1. hydrochloric acid + sodium hydroxide to sodium chloride + water
  2. sulfuric acid + zinc oxide to zinc sulphate + water
    1. sulfuric acid + calcium hydroxide to calcium sulphate + water
  3. Nitric acid + magnesium oxide to magnesium nitrate + water
    1. nitric acid + potassium hydroxide to potassium nitrate + water
  4. Ammonia can be neutralised with HNO3 to make fertiliser
    1. Ammonia dissolves in water to make an alkaline solution
      1. When it reacts with nitric acid you get a neutral salt
        Ammonia + nitric acid to Ammonium nitrate
        NH3 (aq) + HNO3 (aq) to NH4NO3 (aq)
        No water is produced
    2. Ammonium nitrate is an especially good fertiliser because it has nitrogen from two sources the ammonia and the nitric acid. Plants need nitrogen to make proteins
Making salts
1. Making soluble salts using a metal or an insoluble base
  1. Enter text here

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Acids and Alkalis

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	Created by sian.allison over 10 years ago