Paper 1

• Oxidation reaction


  The gaining of oxygen in a reaction
• Oxidation reaction


  Copper + oxygen → copper oxide
• Reduction reaction


  The loss of oxygen in a reaction
• Reduction reaction


  Magnesium oxide → magnesium + oxygen
• Metals in order of reactivity

  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Zinc
  • Iron
  • Copper
• Hydrogen and carbon are sometimes included in the reactivity series because they are used in the extraction of the metals
• Where hydrogen and carbon could go on the reactivity series

  Arrows placed on the reactivity series
• Gold is often found in its pure state because it is a very unreactive metal
• Reaction of a metal with an acid

  Acid + metal → salt + hydrogen
• The speed of the reaction is shown by the rate that hydrogen gas is given off, the more reactive the metal the faster the reaction
• pH scale labels


  • Strong acid (0-3)
  • Strong alkali (12-14)
  • Neutral (7)
  • Weak acid (4-6)
  • Weak alkali (8-11)

  
• pH


  The measure of H+ ions in the solution
• Methods to measure pH

  • Universal indicator
  • pH meter
• Making a soluble salt from an insoluble base

  1. Choose an acid

  2. Choose an insoluble base

  3. Warm the acid

  4. Add the insoluble base until no further reaction

  5. Filter the mixture

  6. Evaporate the water

  7. Crystals of salt form
• Neutralisation reaction


  Acid + base → salt + water
• Word equations


  • Zinc carbonate + sulfuric acid → zinc sulfate + water + carbon dioxide
  • Magnesium oxide + hydrochloric acid → magnesium chloride + water
  • Magnesium carbonate + nitric acid → magnesium nitrate + water + carbon dioxide
  • Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Some metals react with water to produce metal hydroxide and hydrogen
• Some metals react with acid to produce salt and hydrogen
• Displacement reactions


  The metal has to be more reactive than the metal in the compound to take its place
• Aluminium extraction by electrolysis

  1. Positive Al3+ ions attracted to negative electrode, gain 3 electrons to become neutral Al

  2. Negative O2- ions attracted to positive electrode, lose 2 electrons to become neutral O2
• Why aluminium oxide is mixed with cryolite

  To lower the melting point
• Overall equation for electrolysis of Al2O3

  2Al2O3 → 4Al + 3O2
• Aluminium cannot be extracted by carbon because it is more reactive than carbon
• Reaction at negative electrode

  Al3+ + 3e- → Al
• Reaction at positive electrode

  2O2- → O2 + 4e-
• Electricity passed through solution causes positive ions to go to negative electrode where they gain electrons, and negative ions to go to positive electrode where they lose electrons
• pH


  Measure of H+ ion concentration
• pH change from 4 to 2 increases H+ concentration by a factor of 1000
• Strong acid has lower pH than weaker acid at same concentration
• Acids produce H+ in aqueous solutions
• Alkalis produce OH- in aqueous solutions
• In copper sulfate solution


  Cathode: copper forms, Anode: oxygen and water form
• Copper is less reactive than hydrogen so copper forms at cathode
• In sodium chloride solution

  Cathode: hydrogen forms, Anode: chlorine forms
• Sodium is more reactive than hydrogen so hydrogen forms at cathode
• Tests for gases


  • Chlorine: bleaches damp litmus paper
  • Hydrogen: squeaky pop test
  • Oxygen: relight a glowing splint
• Strong acids are completely/partially ionised in aqueous solution
• Weak acids are completely/partially ionised in aqueous solution