Chemical changes

• what is oxidation, reduction and redox in term of oxygen

  oxidation = gain of oxygen

  reduction = loss of oxygen

  redox = gain and loss of oxygen in the same equation
• a displacement reaction is when a more reactive metal displaces a less reactive element in a reaction
• how to extract metals less and more reactive than carbon

  less = reduction via carbon

  more = electrolysis
• what is oxidation and reduction in terms of electrons

  oxidation = loss of electrons

  reduction = gain of electrons
• Acids always form H+ ions in aqueous solution
• a base is anything that neutralises an acid
• alkali is a base that is soluble in water
• bases form OH- ions in aqueous solutions
• How can pH be determined

  By an indicator e.g universal indicator or pH probe
• what is the neutralization reaction

  H+ + OH- = H2O
• BAWS reaction


  base + acid -> water + salt
• MASH reaction


  Metal + acid -> salt + hydrogen
• MCA S' WCD reaction

  metal carbonate + acid -> salt + water + carbon dioxide
• A strong acid fully dissociates into H+ ions
• A weak acid partially dissociates into H+ ions
• As the pH scale decreases by one unit, concentration of H+ ions increase by 10x
• a dilute acid has more solution than acid
• a concentrated acid has more acid than solution
• electrolysis is using electricity to separate elements in ionic substances
• an electrolyte is molten or dissolved ionic substances
• the electrodes are solid conductors. Positive = anode Negative = Cathode
• Electrolysis of lead bromide (molten)

  1. contains Pb2+ and Br- ions
  2. ions are attracted to oppositely charged electrodes
  3. ions become discharged reverting to an atom
  4. lead sinks to the bottom and bromine fuses as its diatomic and floats away
• Electrolysis of Aluminum oxide

  1. molten aluminum mixed with cryolite which reduces melting point which makes it cheaper
  2. the ions are Al3+ and O2-
  3. aluminum is attracted to the cathode where it will sink and drain out the gap
  4. oxygen is attracted to the anode where it reacts with the carbon anode forming CO2 and causes the anode to wear away
• what ions will also be present in aqueous electrolysis

  H+ and OH- ions
• At the anode, if halide is present, halogen gas will be emitted if no halide, O2 and H2O produced
• at the anode, if the metal is more reactive than hydrogen, hydrogen gas will be effervesced, if it's less reactive, however, pure metal will coat the cathode
• Electrolysis of copper sulphate (Aqueous)

  O2 and H2O produced at anode and pure copper is formed at cathode
• electrolysis of sodium chloride (Aqueous)

  hydrogen produced at the cathode and chlorine gas is produced at anode