why are air bubbles in the buret tip a source of error in a titration experiment?
The correct answer and explanation is:
Air bubbles in the buret tip cause errors in a titration experiment because they affect the accuracy of the volume measurement. When performing a titration, the goal is to deliver an exact volume of titrant from the buret into the solution being analyzed. If air bubbles are present in the buret tip, they occupy space that should be filled by the liquid titrant. This means that when the liquid is dispensed, some volume is lost to the air bubble instead of the titrant solution. As a result, the volume recorded on the buret will be higher than the actual volume of titrant delivered.
This error leads to an inaccurate calculation of the concentration of the unknown solution. Since the titration calculation depends on the precise volume of titrant added, an overestimation or underestimation of this volume results in incorrect stoichiometric calculations. If the volume is overestimated due to air bubbles, the calculated concentration of the analyte will be lower than it truly is because it appears more titrant was used. Conversely, if the bubble bursts unexpectedly or changes volume during titration, it can cause irregular delivery of titrant, further reducing accuracy.
Air bubbles can also cause inconsistent flow rates, making it difficult to add titrant dropwise during the final stages of titration. This inconsistency makes reaching the endpoint precisely more challenging. The endpoint is the point at which the reaction is complete, often indicated by a color change. Precision in reaching this endpoint is critical for accurate results.
To avoid this error, the buret should be carefully filled and checked for air bubbles before beginning the titration. Any bubbles in the tip should be removed by allowing some titrant to flow through until the bubbles are expelled. This ensures that the volume recorded corresponds exactly to the liquid titrant delivered, improving the accuracy and reliability of the titration results.