General

• Oxidation


  When a substance gains oxygen
• Reduction


  When a substance loses oxygen
• Displacement reaction

  A reaction where a more reactive metal displaces a less reactive metal from a compound
• Unreactive metals are found in their natural state in Earth
• Extracting metals less reactive than carbon

  Reduction with carbon. Carbon displaces the metal in a metal oxide - gets oxidised to carbon oxides. Metal from the metal oxide gets reduced to the pure metal.
• Extracting metals more reactive than carbon

  By electrolysis
• Oxidation


  Loss of electrons
• Reduction

  Gain of electrons
• Reaction between metals and acids

  Metal + acid → salt + hydrogen

  Redox reaction, also a displacement reaction
• Metals that will react with acid

  • Those above hydrogen in the reactivity series
• Neutralisation reaction

  Base + acid → salt + water
• Reaction between metal carbonate and acid

  Metal carbonate + acid → salt + water + carbon dioxide
• Reaction between metal oxides and acids

  Metal oxide + acid → a salt + water
• Redox reaction

  A reaction where both oxidation and reduction occurs
• When magnesium reacts with hydrochloric acid, magnesium has been oxidised (Mg to Mg2+) and the hydrogen in HCl has been reduced (H+ to H2)
• Forming a soluble salt

  React the excess acid with some insoluble chemical (e.g. metal oxide)

  1. Filter off the leftovers
  2. Crystallise the product
• Acids and alkalis in aqueous solutions

  Acids produce hydrogen ions, alkalis produce hydroxide ions
• Bases, acids and alkalis

  Bases are compounds that neutralise acids, acids produce hydrogen ions in aqueous solutions, alkalis are soluble bases - produce hydroxide ions in aqueous solutions
• pH scale

  The measure of acidity/alkalinity of a solution; neutral solution has a pH of 7
• Neutralisation reaction (ionic form)

  H+ + OH− → H2O
• Strong acid and weak acid

  Strong acid is completely ionised in aqueous solution; weak acid is only partially ionised in aqueous solution
• Neutralisation reaction

  H+ + OH− → H2O
• Strong acid

  Completely ionised in aqueous solution
• Weak acid

  Only partially ionised in aqueous solution
• Concentrated acid

  Has more moles of acid per unit volume than dilute
• Dilute acid

  Solution of low concentration
• Electrolysis

  Passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these
• Electrolyte

  The liquid/solution which conducts electricity
• Cathode

  Negative electrode
• Anode

  Positive electrode
• Electrolysis

  1. Reduction occurs at the cathode

  2. Oxidation occurs at the anode
• Aluminium manufacturing

  Electrolysis of aluminium oxide and cryolite
• Why aluminium is expensive

  Lots of energy is needed to produce the current in electrolysis
• Aluminium extraction

  1. Al3+ + 3 e− → Al (cathode)

  2. 2 O2− → O2 + 4 e− (anode)
• Why cryolite is used

  It lowers the melting point of aluminium oxide, reducing energy costs
• Electrolysis of aqueous Na2SO4

  1. 2 H+ + 2 e− → H2 (cathode)

  2. 4 OH− → 2 H2O + O2 + 4 e− (anode)
• Electrolysis of molten and aqueous KCl

  1. K+ + e− → K (cathode)

  2. 2 Cl− → Cl2 + 2 e− (anode)

  3. 2 H+ + 2 e− → H2 (cathode)

  4. 2 Cl− → Cl2 + 2 e− (anode)
• Electrolysis of aqueous CuBr2


  1. Cu2+ + 2 e− → Cu (cathode)

  2. 2 Br− → Br2 + 2 e− (anode)