Titration procedures

  • A way of finding the concentration of an unknown solution (acid or base) by measuring the volume of the unknown that is required to react with a known volume of a standard solution (that we do know the concentration of)
  • Called ‘volumetric analysis’

Procedures

Preparation of a primary standard
  • Calculate the exact mass of solid needed to make the required volume of the concentration of solution needed
  • Weigh out, accurately, approximately this mass
  • Dissolve the weighed primary standard solid with distilled water in a beaker, then transfer this to a volumetric flask
  • Make up the solution to the mark with distilled water, adding the last few drops with a Pasteur pipette
  • Calculate the exact concentration of the solution, using the mass and the volume
Titration of an unknown solution with the primary standard
  • Choose which reagent solution will be delivered from the burette and rinse the burette with that solution before filling it
  • Use a pipette to transfer a known volume of the other solution into a conical flask. Rinse the flask with distilled water, and the pipette with the analyte.
  • Add two or three drops of suitable indicator (see next tabs) in the flask
  • Do the titration. Stop when the indicator changes colour (the endpoint)
  • Record the volume reading on the burette, to two decimal places using a magnifying glass and the black line
  • Repeat at least 3 times
  • Average the titre results
  • Hence calculate the concentration of the unknown solution
  • This unknown solution can then be used as a secondary standard

Procedures to minimise error

Rinsing procedures
  • Rinse all equipment with tap then distilled water first
  • Rinse delivery equipment (pipette and burette) before use with the solution going to be in it (usually the analyte¬†and titrant, respectively)
  • Rinse volumetric flask and conical flask with distilled water
  • Rinse storage equipment (stock bottle) with the solution being stored in it

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