RP9: Exam Questions

Question 1

Suggest why the pH probe is washed with distilled water in between each of the calibration measurements.

Answer 1

To remove any OH- or H+ ions that may have remained on the probe which could interfere with readings.

Question 2

Explain why the volume of sodium hydroxide solution added between each pH measurement is smaller as the end point of the titration is reached.

Answer 2

So the end point of neutralisation can accurately be determined.