Question

a student performed the titration as in this experiment. after adding 10 ml of naoh solution from the buret, the sample in the flask still had not turned pink. identify two sources of possible error that may have occurred in this experiment.

Answer 1

Two common sources of error in a titration where the indicator does not change color could be the use of the incorrect indicator for the pH range or insufficient stirring to properly mix the solutions.

Step-by-step explanation:

If a student performed a titration and after adding 10 mL of NaOH solution the sample in the flask had not yet turned pink, two sources of possible error in the experiment may include the following:

• Incorrect use of the indicator: If the pH of the solution is not within the correct range for the indicator, the color change may not be observed. For example, phenolphthalein is suitable for a pH between 8.2 and 10, so if the pH of the solution after adding NaOH is not within this range, the expected pink color will not appear.
• Insufficient stirring: During titration, it is essential to stir the solution constantly to ensure that the titrant is thoroughly mixed with the analyte. If stirring is not adequate, the color change might not be noticed immediately, giving a false impression that the endpoint has not been reached.

Additional errors could include misreading the burette or not allowing the reaction to reach completion before concluding that the endpoint has not been reached.