RP 9 - Titration curves

Question 1

constructing a pH curve method

Answer 1

• transfer 25cm3 of acid to a conical flask with a volumetric pipette
• measure initial pH of the acid with a pH meter
• add alkali in small amounts noting the volume added
• stir mixture to equalise the pH
• measure and record the pH to 1dp
• repeat steps 3-5 but when approaching end point add in smaller volumes of alkali
• add until alkali in excess

Question 2

why should u calibrate meter first by measuring known pH of a buffer solution

Answer 2

• necessary because pH meters can lose accuracy on storage
• most pH probes are calibrated by putting probe in a set buffer and pressing a calibration button / setting for that pH.
• sometimes this is repeated with a second buffer at a diff pH
• can also improve accuracy by maintaining constant temp