Accurate Determination of the End-Point of Titrations

Accurate Determination of the End-Point of Titrations

Section 1: End-Point of Titrations

  • End-Point of a Titration: The point in the titration process where the reaction between the titrant and the analyte is complete, indicated by a change in colour due to the indicator added.
  • Colour Change: During a titration, the indicator used changes colour, signifying the end-point. This shift marks the exact moment when all the analyte has reacted with the titrant.
  • Selection of Indicator: Choosing the correct indicator is crucial because different indicators change colour at different pH levels. The indicator should match the pH at the equivalence point of the titration.

Section 2: Judging the End-point

  • Colour Consistency: The end-point has been reached when the colour change remains consistent after swirling. This might take a drop or two beyond the initial hint of a colour change, indicating that the solution has adequate titrant.
  • Overshooting the End-point: If too much titrant is added, the solution could go past the end-point, and the titration would have to be repeated. This is known as overshooting and should be avoided.
  • End-Point Recognition: Rapid addition of titrant can be done initially, but the titrant should be added dropwise as the end-point nears to ensure accurate determination.

Section 3: Achieving Accuracy

  • Repetition of Titration: To ensure accuracy of results, the titration process should be repeated several times. The mean titre is then calculated from consistent results, excluding any anomalies.
  • Noting Measurements: Precisely note down volume readings from the burette at the beginning and end of the titration to calculate the volume of titrant used.
  • Instrument Calibration: Burettes used in titration should be regularly checked and calibrated to ensure accurate measurements.

Section 4: Errors and Corrections in Titration

  • Parallax Errors: These occur when the measurement scale is not viewed from straight ahead. Ensure the meniscus of the liquid in the burette is at eye level when reading the volume.
  • Recording Errors: Mistakes while noting down the initial and final readings could lead to big variations in results. Double-check readings before recording.
  • Handling Errors: Mishandling of apparatus, especially while dispensing drops towards the end-point can result in inaccurate results. Therefore, exercise care while conducting the experiment.