Titrations

• Concentration is a measure of how crowded a solution is. It is measured in g/dm3
• m = CV

  mass = Concentration x Volume
• A standard solution has a known concentration.
• cm3 -> dm3

  cm3 / 1000 = dm3

  1000cm3 = 1dm3
• Titrations are used to find out concentrations.
• Titration step by step

  1. Using a pipette, measure out a set volume of alkali into a flask.
  2. Add a few drops of indicator (eg. methyl orange).
  3. Fill a burette with a standard solution (known concentration) of acid.
  4. Use the burette to add the acid to the alkali, drop by drop, whilst swirling the flask (to mix the solution).
  5. The indicator will change colour when all the alkali is neutralised (methyl orange turns red)
  6. Record the volume of acid used to neutralise the alkali.
  7. Repeat a few times, until you get concordant results.
• Indicator

  Methyl Orange

  • yellow to red

  Phenolphthalein

  • pink to colourless
• Concordant results are within 0.1 cm3.
• n = CV

  moles = Concentration x Volume
• V = nMr

  Volume = moles x Molar volume
• One mole of any gas occupies 24dm3 at room temperature and pressure.

  V = 24n

  Volume = 24 x moles