Titration
2 marks · NormalDescribe two key steps you would take to accurately find the volume of sulfuric acid needed to neutralise a fixed amount of sodium hydroxide solution using a titration. Do not include any calculation steps.
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Also accept: Take an initial reading of sulfuric acid in the burette before starting the titration.; Add sulfuric acid slowly near the endpoint and note the volume at which the indicator changes colour.; Ensure the sodium hydroxide is measured using a pipette and placed into a conical flask; add indicator.; Swirl the flask while adding acid to mix thoroughly.
Common mistakes: Describing calculation or recording of result, not procedural steps.; Describing use of universal indicator.
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Marking points
M1 · 1 mark · Describes measuring or reading the initial volume or using a pipette to measure alkali.
M2 · 1 mark · Describes adding acid until indicator changes colour (endpoint) or adding acid dropwise near endpoint and taking final reading.
Worked solution
1. Measure 25.0 cm^3 of sodium hydroxide solution using a pipette and transfer it into a conical flask. Add a few drops of suitable indicator (such as phenolphthalein). 2. Fill a burette with sulfuric acid and take the initial burette reading. Add sulfuric acid from the burette to the alkali, swirling the flask, adding dropwise near the endpoint until the indicator just changes colour. Then, take the final burette reading to determine the volume added.