GCSE: OCR gateway: C3: percentage yield and atom economy + energy

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  • C3
    • Percentage yield and atom economy
      • Calculating Percentage Yield and Industrial Costs
        • Used to find out the amount of product should be made from a chemical reaction
          • In reallife it is less as practical methords used produces loss
        • Percentage Yield: (actual yield/predicted yield)*100
        • Industrial proccess have a high percentage yield so
          • They reduce the amount of reactants wasted; cost
          • Reduce costs by making sure enough reactants used; to little reduces product amount
      • Atom Economy
        • (M of desired products/M of all products)*100
        • Industry wants high atom economy
          • Reduce production of unwanted products; cost
          • Proccess more sustainable by better use of reactants; conserving raw materials
    • Energy
      • Making and Breaking Bonds
        • Bond breaking is endothermic
        • Bond making is exothermic
        • To decide whether reaction is endo or exo amount of energy made and produced is compared
          • Energy needed to break reactants into seperate atoms
            • Atoms join to form bonds releasing energy
              • More energy released then needed is exo
              • More energy needed then released is endo
      • Finding Energy Released by Fuels
        • Energy transferred (J) = mass of water heated(g) * specific heat capacity of water(J/g^c);4.2 * temperature change
        • Energy released by solid fuel
          • Find mass of 1g of fuel
            • Pour 100g of water into copper calorimeter (1cm3=1g)
              • Heat water with burning fuel
                • Measure temperature rise
                  • Repeate with different fuels to ensure fair testing; same distance from flame
                    • Ensure reliability by repeating resutls
                      • Fuel burnt = fuel mass before - fuel mass after
        • Energy in fuel: Energy per gram = energy released(J)/mass of fuel burnt (g)


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