Chemistry – Experimental techniques and chemical analysis - Acid-base titrations | e-Consult

To accurately identify the end-point of a titration using an indicator, follow these steps:

1. Preparation: Ensure the burette is filled with the titrant (the solution of known concentration) and any air bubbles are removed. The pipette should be accurately filled with the solution of unknown concentration. Record the initial and final readings of the burette.
2. Titration Process: Slowly add the titrant from the burette to the analyte (the solution of unknown concentration) in the conical flask, while continuously swirling the flask. Maintain a consistent and slow addition rate.
3. Indicator Action: An appropriate indicator should be present in the analyte solution. The indicator changes colour over a specific pH range, signalling the completion of the reaction.
4. Observing the Colour Change: As the titrant is added, observe the colour change in the conical flask. The colour change will be gradual at first, becoming more pronounced as the end-point is approached.
5. Identifying the End-Point: The end-point is reached when the indicator changes colour permanently and consistently. This is the point where the reaction is complete. It's crucial to observe the colour change carefully and avoid making a decision too early or too late. A sharp, distinct colour change is preferable.
6. Final Reading: Once the end-point is identified, record the final reading of the burette. Calculate the volume of titrant used.
7. Repeat Titrations: Perform multiple titrations (at least three) to ensure accuracy and reliability of the results. Calculate the average volume of titrant used.

Important Factors:

• Stirring Speed: Maintain a consistent, moderate stirring speed throughout the titration. This ensures thorough mixing of the reactants and helps the indicator to distribute evenly.
• Lighting: Titrate in good lighting conditions to clearly observe the colour change.
• Observer Position: Position yourself so that you can clearly see the colour change without shadows or obstructions.