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AS & A Level · AS/A Level

Chemistry

Stoichiometry and analytical measurement

Name: ____________________Date: October 10, 2026
  1. 1.

    Calculate the amount in moles in 5.85 g of NaCl using Mr = 58.5.

    [2 marks]
  2. 2.

    Explain why a burette is rinsed with the titrant before filling, rather than leaving distilled water inside.

    [3 marks] · no calculator
  3. 3.

    25.0 cm^3 of H2SO4 is neutralised by 30.0 cm^3 of 0.200 mol dm^-3 NaOH. Calculate the acid concentration; H2SO4 + 2NaOH -> Na2SO4 + 2H2O.

    [3 marks]
  4. 4.

    A 20.00 cm^3 titre comes from two burette readings, each with absolute uncertainty +/-0.05 cm^3. Calculate the worst-case percentage uncertainty in the titre.

    [3 marks]
  5. 5.

    10.0 g CaCO3 (M = 100 g mol^-1) reacts with 0.150 mol HCl: CaCO3 + 2HCl -> CaCl2 + CO2 + H2O. Calculate the maximum CO2 volume at 24.0 dm^3 mol^-1 and identify the limiting reagent.

    [4 marks]
  6. 6.

    A carbonate sample contains an insoluble inert impurity. A student weighs the sample, reacts it with excess acid and measures collected CO2. Evaluate two reasons why a low gas yield does not establish the impurity percentage reliably.

    [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.

Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.