RP 2 - Carrying out a titration

• sulfuric acid + sodium hydroxide -> sodium sulfate and water
• why do we do a titration?

  • we have a certain volume of sodium hydroxide and we know the concentration
  • if we know the volume of sulfuric acid needed to neutralise the alkali, we can use this to work out the concentration of the acid
• why do we use a conical flask?

  reduces the risk of splashing
• pipette

  • normally would use a pipette filler to draw liquid into the pipette
  • very important allow liquid to drain out of pipette instead of blowing it out using using the pipette filler
  • blowing it out would give incorrect volume
• method:

  1. use pipette to transfer 25cm3 of sodium hydroxide solution to a conical flask.
  2. add five drops of indicator e.g. methyl orange to the alkali in the conical flask and place on white tile so can see a colour change more clearly.
  3. fill a burette with sulfuric acid.
  4. add acid until the solution is neutral - need to add just enough acid : once we see a colour change, now add the acid drop by drop until solution neutral - important to swirl the solution to make sure the acid and alkali mix.
  5. read the volume of acid added from the burette.
• reading the burette

  • need to make sure your eye is level with the surface of the liquid - natural curve called meniscus
  • read at the bottom of the meniscus.
• repeating titration

  • repeat titration until we can readings within 0.1 cm3 of eachother - then take a mean of these for our final volume.