Titration

• State why it is important to fill the space below the tap in the burette with solution A before beginning an accurate titration

  Space will fill during titration

  volumes added are too high
• Suggest one reason why a 250 cm3 conical flask is preferred to a 250 cm3 beaker for a titration.

  Less chance of losing liquid on swirling
• During a titration, a chemist rinsed the inside of the conical flask with deionised water. The water used for rinsing remained in the conical flask.(i) Give one reason why this rinsing can improve the accuracy of the end-point.

  Returns reagent on the sides of the flask to the reaction mixture
• Explain why the water used for rinsing has no effect on the accuracy of the titre

  This does not change the number of moles of reagents

  water is not a reagent

  water is one of the products
• Suggest one reason why repeating a titration makes the value of the average titre more reliable

  a single titration could be flawed / anomalous

  to obtain concordant results
• A teacher noticed that a student had not cleared a large air bubble from below the burette tap in preparing the burette for use before starting the titration. This air bubble was ejected during the first titration of the volumetric flask mixture.

  (a) State the effect that this mistake would have on the value of the first titre

  (b) State and explain the effect, if any, that this mistake would have on the average titre for this experiment.

  a --> The value of the titre would be higherb --> No effect, The first titration can be ignored
• The maximum errors for the pipette and the burette are shown below. These errors take into account multiple measurements .

  Pipette ± 0.05 cm3Burette ± 0.15 cm3

  Estimate the maximum percentage error in using each of these pieces of apparatus.

  Use an average titre 24.25 cm3 to calculate the percentage error in using the burette.

  Answer: