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• Concentration


  Measured in moles per given volume of solution e.g. moles per dm3 (mol/dm3)
• Calculating moles of solute in a given volume of a known concentration


  Moles = conc x vol (think about the units)
• Smaller volume or larger number of moles of solute


  Gives a higher concentration
• Larger volume or smaller number of moles of solute


  Gives a lower concentration
• Converting concentration from g dm-3 to mol dm-3

  Divide by molar mass in grams
• Converting concentration from mol dm-3 to g dm-3

  Multiply by molar mass in grams
• Acid-alkali titration


  1. Add acid to burette using a funnel, record volume

  2. Add known volume of alkali to conical flask and add indicator

  3. Place flask on white tile

  4. Add acid to alkali until end point

  5. Calculate titre (amount of acid added)
• Calculating unknown concentration or volume from titration results

  1. Calculate moles of acid using moles = conc x vol

  2. Use mole ratio from reaction equation to calculate moles of alkali

  3. Calculate concentration of alkali using conc = mol / vol
• Percentage yield


  Amount of product produced / Maximum amount of product possible x 100
• Actual yield is usually less than theoretical yield
• Causes of actual yield being less than theoretical yield

  • Incomplete reactions
  • Practical losses during the experiment
  • Competing, unwanted reactions (side reactions)
• Atom economy


  A measure of the amount of starting materials that end up as useful products
• Calculating atom economy


  Atom economy = (Mr of desired product from reaction / sum of Mr of all reactants) x 100
• Reactions with high atom economy are important for sustainable development and economic reasons
• Factors to consider when choosing a reaction pathway

  • High atom economy
  • High yield
  • Fast rate
  • Equilibrium position to the right (towards products)
  • Useful by-products
• Molar volume


  The volume occupied by one mole of molecules of any gas at room temperature and pressure
• Equal amounts in mol. of gases occupy the same volume under the same conditions of temperature and pressure (e.g. RTP)
• Chemical cell


  Produces a voltage until one of the reactants is used up
• Volume of 1 mol. of any gas at RTP (room temperature and pressure: 20 degrees C and 1 atmosphere pressure) is 24 dm3
• Chemical reactions in a chemical cell


  Stop when one of the reactants has been used up
• Calculating volume of gas at RTP

  1. Volume (dm3) of gas at RTP = Mol. x 24

  2. Volume (cm3) of gas at RTP = mol x 24,000
• Hydrogen-oxygen fuel cell


  Uses hydrogen and oxygen to produce a voltage, with water as the only product
• Hydrogen-oxygen fuel cell


  • Supplied by an external source of fuel (e.g. hydrogen) and oxygen or air
  • The reaction takes place within the fuel cell to produce a potential difference
  • Overall reaction involves the oxidation of hydrogen to produce water
• Using molar volume and balanced equations in calculations involving masses of solids and volumes of gases


  1. Calculate moles of reactant

  2. Work out mole ratio and calculate moles of product

  3. Calculate mass/volume using moles
• 2H2 + O2 → 2H2O
• Strengths of fuel cells

  • Produce only water as waste
  • Keep producing fuel if fuel keeps being supplied
• Avogadro's law


  One mole of a substance contains 6.02 x 10^23 particles
• Weaknesses of fuel cells

  • Difficult to transport/store hydrogen so aren't suitable for portable devices
  • Expensive to make
• Transition metals


  • High melting point
  • High density
  • Ions with many different charges
  • Form coloured compounds
  • Useful as catalysts
• Most metals are transition metals
• The oxidation of metals results in corrosion
• Corrosion


  Destruction of materials by chemical reactions with substances in the environment
• Corrosion


  • Rusting
• Rusting of iron


  1. Air and water are necessary

  2. Oxidation - gain of oxygen results in corrosion
• Ways to prevent rusting of iron

  • Exclusion of oxygen
  • Exclusion of water
  • Sacrificial protection
• Sacrificial protection


  The metal you want to be protected from rusting is galvanised with a more reactive metal, which will rust first and prevent water and oxygen reaching the layer underneath
• Electroplating


  • Acts as a barrier to exclude oxygen and water
  • Improves appearance by plating with an unreactive metal like gold
• How electroplating is done

  1. Metal to be plated as the cathode

  2. Metal you're plating with as the anode

  3. Solution containing ions of the metal being used for plating
• Why converting pure metals into alloys increases strength

  In a pure metal, all the metal ions are the same size and in a regular arrangement, allowing the layers to slide over each other easily, making the metal soft and malleable. In an alloy, you have metal ions of different sizes, which disrupts the regular structure and prevents the ions being able to slide as easily, leaving a much harder, stronger metal.
• Most metals in everyday uses are alloys