Quantitative analysis
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A student wished to determine the mass of pure sulfamic acid (H3NSO3\text{H}_3\text{NSO}_3H3​NSO3​) in a sample of household kettle descaler containing inert, soluble impurities.

The student used the following method:

  • Step 1 Weigh the sample of impure kettle descaler.
  • Step 2 Dissolve the sample in 250 cm3 of distilled water in a beaker.
  • Step 3 Use a measuring cylinder to transfer 25.0 cm3 of this solution into a conical flask.
  • Step 4 Add 3 drops of phenolphthalein indicator to the flask.
  • Step 5 Fill a burette with standard sodium hydroxide solution of known concentration.
  • Step 6 Titrate the sulfamic acid solution, swirling continuously.
  • Step 7 Record the volume of sodium hydroxide required to reach the end-point.
  • Step 8 Use this single titration reading to calculate the percentage purity of the sulfamic acid.

Suggest three improvements the student could make to this method to obtain a more accurate value for the mass of pure sulfamic acid.

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Quantitative analysis Questions

Practise Edexcel GCSE Chemistry Quantitative analysis with exam-style questions for Foundation and Higher tier. 100 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

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Quantitative analysis Questions

  1. GCSE
  2. /Chemistry
  3. /Quantitative analysis