Titration
2 marks · HardState two steps you must carry out before starting to add alkali from a burette in a titration experiment between hydrochloric acid and sodium hydroxide. Do not include steps taken during or after the addition of alkali.
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Also accept: Rinse pipette and burette with appropriate solutions; Measure out a known volume of acid with a pipette; Transfer acid to conical flask; Add indicator to conical flask; Record initial burette reading; Clean and rinse all glassware; Fill burette with sodium hydroxide solution and remove air bubbles
Common mistakes: Including steps from during or after addition, e.g. 'add alkali dropwise' or 'record final reading'; Including step of reading burette after addition only
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Marking points
B1 · 1 mark · States any one correct preparatory step taken before beginning to add alkali from burette (e.g., wash/prepare pipette, transfer acid to flask, add indicator, fill burette)
B2 · 1 mark · States a second different correct preparatory step (see above), not a repeat or overlap of the first
Worked solution
Before starting to add alkali from the burette, you must first (1) measure a known volume of hydrochloric acid using a pipette and transfer it to a conical flask, and (2) add a few drops of indicator such as phenolphthalein to the flask. Alternatively, you could mention filling/rinsing the burette with sodium hydroxide solution and recording the initial burette reading.