Titration Technique

The Acidic Environment‎ > ‎4. Acid/Base Definitions‎ >

Describe the correct technique for conducting titrations and preparation of standard solutions

• Standard solution: A solution with an accurately known concentration.
• Primary standard solution: A solution prepared from a solid that:
  • Is water-soluble.
  • Has a high purity.
  • Has a known formula.
  • Is stable in air.
• A primary standard solution can be prepared using the following procedure:
  • Determine the mass of primary standard required to form the desired primary standard solution concentration.
  • Weigh the required amount of primary standard into a beaker.
  • Dissolve the primary standard in a small amount of water.
  • Transfer all of the solution from the beaker to a volumetric flask, washing residue into the flask using distilled water.
  • Add distilled water to the volumetric flask until the meniscus of the water is level with the calibration mark.
• Titration: A volumetric analytical technique used to determine the concentration of a solution by reacting it with a standard solution.
• Secondary standard solution:  A solution that has had its concentration determined by a titration with a primary standard solution.
• The end-point of a titration is indicated by a change in colour of an indicator solution.
• An indicator is selected that changes colour at the pH of the salt solution formed at point of neutralisation (equivalence point):

• Titration procedures involve several pieces of volumetric glassware:
  • Pipette: A volumetric glassware item used to transfer a known volume of a solution into a conical flask.
  • Burette: A volumetric glassware item used to transfer one solution into another at a controlled rate.
• All glassware used in titration procedures needs to be washed thoroughly before use, first with normal water, then with distilled water.
• A titration of a strong basic standard solution and a weak acidic solution of unknown concentration can be performed using the following procedure:
  • Add a known volume of the acidic solution into a conical flask using a pipette.
  • Add a few drops of phenolphthalein indicator to the conical flask.
  • Fill a burette with the basic solution to the highest calibration mark.
  • Use the burette to add the basic solution to the acidic solution until the equivalence point is reached, indicated by a change in indicator colour from colourless to red.
  • Record the volume of acidic solution used to reach the equivalence point.
  • Repeat the above procedure several times, slowing the transfer rate from the burette when the previously transferred volume is neared.
  • Using the concentration of the basic solution, the volumes of both solutions, and the equation of the neutralisation reaction, determine the concentration of the acidic solution.

Titration with phenolphthalein indicator, and titration curve