Chemical Changes

• Metals by reactivity

  • Most reactive
  • Less reactive
• Metals above carbon in reactivity series

  • Need electrolysis to be extracted
• Metals below carbon in reactivity series


  • Can be extracted by reduction
• Unreactive metals


  • Generally found in earth as pure ores, unreacted with anything
• Reactive metals


  • Generally found combined with oxygen as metal oxides
• Metal more reactive than hydrogen


  Hydrogen gas produced in electrolysis
• Metal less reactive than hydrogen


  Something else produced as gas in electrolysis
• More reactive metal


  Displaces less reactive metal in a reaction
• Less reactive metal


  Cannot displace more reactive metal in a reaction
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Anode


  Positive electrode
• Cathode


  Negative electrode
• Balancing half-equations in electrolysis


  1. Balance elements

  2. Make charge neutral by adding electrons

  3. Determine if oxidation or reduction
• Acid + metal = salt + hydrogen
• Acid + metal oxide = salt + water
• Acid + metal hydroxide = salt + water
• Acid + metal carbonate = salt + water + carbon dioxide
• Making copper sulfate

  1. Heat sulfuric acid

  2. Stir in copper oxide until in excess

  3. Filter to remove excess copper oxide

  4. Evaporate to leave copper sulfate crystals
• pH scale

  1 is acidic, 7 is neutral, 14 is alkaline
• Acidity


  Caused by hydrogen ions
• Alkalinity


  Caused by hydroxide ions
• Acid-base titration


  1. Pipette alkali into flask

  2. Add acid from burette drop by drop

  3. Stop when indicator changes colour permanently
• Titration calculations


  Use moles of acid/alkali to find concentration of unknown
• Strong acids fully dissociate into ions
• Weak acids only partially dissociate into ions
• Conductivity


  Requires molten or dissolved state for ions to move freely
• Aluminium electrolysis

  1. Positive anode attracts oxygen, forming oxygen gas

  2. Negative cathode attracts aluminium ions, forming aluminium metal
• Common electrolysis setups

  • Sodium chloride
  • Sodium sulfate
  • Copper chloride
  • Copper sulfate
• Products of sodium chloride electrolysis: hydrogen gas, chlorine gas, sodium hydroxide
• Products of sodium sulfate electrolysis: hydrogen gas, oxygen gas
• Products of copper chloride electrolysis: copper metal, chlorine gas
• Products of copper sulfate electrolysis: copper metal, oxygen gas
• Electrolysis setup

  • Positive and negative electrodes
  • Indicator light to check electricity flowing
  • Collect and test gases produced