C4

• Theoretical yield - mass of product you expect to be produced

  Not always possible to obtain bc:

  • some of product can be lost when separated from reaction mixture
  • can be unexpected side reactions which produce different products
  • reaction might not be completed bc it’s reversible
• Percentage yield is actual yield in proportion to theoretical yield:

  % yield = (actual yield ÷ theoretical yield) x 100
• Atom economy:

  • tells you what proportion of atoms is useful
  • high atom economy = sustainable bc fewer atoms being wasted
  • % of atom economy = (Mr of useful products ÷ Mr of all products) x 100
• Avogadro’s constant:

  • a constant
  • one mole of substance ALWAYS contains 6.023 x 10^23 molecules/ions/atoms
• Mr = mass ÷ no. of moles
• Excess and limiting reactants:

  • reactant that runs out first is limiting
  • reactant left over is in excess
• Concentration:

  • concentration (g/dm^3) = mass (g) ÷ volume (dm^3)
  • dm^3 = cm^3 ÷ 1000
  • concentration (mol/dm^3) = no. of moles (mol) ÷ volume (dm^3)
  • greater mass of solute = greater number of moles = greater concentration
  • if same no. of moles of solute is dissolved in smaller volume, concentration will be greater
• Gases:

  • at any temp or pressure, same no. of moles in a gas will occupy same volume
  • at room temp and pressure, 1 mole of gas occupies 24 dm^3
  • moles of a gas = volume (dm^3) ÷ 24 dm^3
• REQUIRED PRACTICAL TITRATION (1):

  • use pipette to extract known volume of solution with unknown concentration; pipette measures fixed volume only
  • add solution of unknown concentration to conical flask and put it on a white tile
  • add a few drops of indicator (phenolphthalein) to conical flask
  • add solution with known concentration to burette
  • carry out rough titration to find out what volume of solution in burette needs to be added to solution in conical flask; add solution from burette into conical flask a little at a time until end point is reached
• REQUIRED PRACTICAL TITRATION (2):

  • end pint is when indicator changes colour
  • record end volume of end point as rough value
  • repeat, but add solution in burette drop by drop (more precise)
  • swirl flask in between drops
  • record volume of end point
• Indicators:

  • phenolphthalein - turns colourless in acid and pink in alkali
  • methyl orange - turns red in acid, orange in neutral and yellow in alkali
  • universal indicator - turns red in acid, green in neutral and purple in alkali