SC14

• Theoretical Yield - maximum mass of product that can be formed from a given amount of reactant
• Actual Yield - actual mass of product formed during a reaction
• Percentage yield is never 100% because of:

  • incomplete reactions
  • competing/unwanted side reactions
  • practical losses (fewer reaction steps means less waste product and higher yield/atom economy)
• Atom Economy - mass percentage of useful products formed in a reaction

  
• Atom Economy is used to determine the reaction pathway as:

  • raw materials are expensive so more waste product is less profitable
  • less sustainable if large quantities of reactants create tiny amounts of products
  • waste products are expensive to dispose of

  Solutions include using a more efficient reaction or finding a use for the waste products instead of paying to dispose of it
• Atom Economy Factors:

  • percentage yield
  • cost of raw materials
  • the position of equilibrium
  • rate of reaction
  • cost of maintaining the right conditions (e.g. temperature/pressure)
• The concentration of a solution is measured in moles per cubic decimetre and the volume is in decimetres cubed.

  • moles = concentration (mol/dm3) x volume (dm3)

  Concentration can also be in grams per cubic decimetre.

  • concentration (g/dm3) = concentration (mol/dm3) x Mr
• Titration Practical:

  1. Use a pipette to transfer 25cm3 of sodium hydroxide into a conical flask
  2. Place the sulfuric acid into a burette
  3. Add a suitable indicator (methyl orange/phenolphthalein)
  4. Add the sulfuric acid from the burette to the conical flask until the colour changes (do this drop by drop near the end point)
  5. Note the final reading and repeat

  Methyl Orange will turn yellow to red

  Phenolphthalein will turn pink to colourless
• In titration, the alkali has a known volume and concentration but the acid only has a known volume.

  If we know the volume of sulfuric acid needed to neutralise the alkali, we can use an equation to work out the acid concentration
• Molar gas volume - the volume occupied by one mole of any gas at room temperature and pressure

  The volume depends on the number of particles, temperature and pressure not the relative formula mass
• Avogadro's Law - at the same temperature and pressure, equal volumes of gases contain an equal number of particles