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Chapter 8 Practice Paper: Titration and concentration — question paper

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GCSE (9–1) · GCSE Chemistry (Foundation and Higher)

Chapter 8 Practice Paper

Titration and concentration

Duration: 40 minutes
Total: 30 marks
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Class:
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READ THESE INSTRUCTIONS FIRST

  • Answer all questions.
  • Section A contains ten multiple-choice questions. Choose one answer, A, B, C or D, for each.
  • Section B contains structured questions. Write your answers in the spaces provided.
  • Questions marked [Chemistry only] are for separate science candidates.
  • The total mark for this paper is 30.

Original practice material written for the MOE GCSE Chemistry syllabus. It is not an official MOE or school examination paper. Chapter 8: concentration in g/dm³, the titration practical and concordant titres, mol/dm³ and titration calculations (Chemistry-only, Higher, badged).

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

  1. 1

    A flask holds 700 cm³ of solution in which 35 g of solid is dissolved. The concentration, in g/dm³, is

    1. A24.5 g/dm³
    2. B50 g/dm³
    3. C35 g/dm³
    4. D5 g/dm³
    ( )
  2. 2

    The volume 25 cm³ expressed in dm³ is

    1. A0.025 dm³
    2. B0.25 dm³
    3. C2.5 dm³
    4. D25 000 dm³
    ( )
  3. 3

    In a titration, the alkali is measured by

    1. Aa measuring cylinder
    2. Ba beaker
    3. Ca pipette
    4. Dthe burette
    ( )
  4. 4

    Titres of 21.60, 21.50 and 21.55 cm³ are obtained. The mean is

    1. A21.60 cm³
    2. B21.50 cm³
    3. C21.22 cm³
    4. D21.55 cm³
    ( )
  5. 5

    The rough titration is discarded because

    1. Ait was rushed and may have overshot the endpoint
    2. Bit used more indicator
    3. Cburettes cannot read that fast
    4. Dit is always too small
    ( )
  6. 6

    0.04 mol in 200 cm³ has a concentration of [Chemistry only]

    1. A0.008 mol/dm³
    2. B2 mol/dm³
    3. C0.04 mol/dm³
    4. D0.2 mol/dm³
    ( )
  7. 7

    NaOH (Mr 40) at 0.25 mol/dm³ equals [Chemistry only]

    1. A0.00625 g/dm³
    2. B10 g/dm³
    3. C40 g/dm³
    4. D160 g/dm³
    ( )
  8. 8

    25.0 cm³ of 0.1 mol/dm³ NaOH contains [Chemistry only]

    1. A2.5 mol
    2. B0.25 mol
    3. C0.0025 mol
    4. D0.025 mol
    ( )
  9. 9

    The conical flask is rinsed with distilled water because water

    1. Aadds no extra moles of alkali, so the titre is unaffected
    2. Bspeeds up the endpoint
    3. Cneutralises the acid early
    4. Dimproves the indicator colour
    ( )
  10. 10

    A salt made by titration (e.g. ammonium chloride) is crystallised from a solution prepared

    1. Awith extra indicator for safety
    2. Bwith excess ammonia solution
    3. Cwith excess hydrochloric acid left in
    4. Dwithout indicator, using the exact volumes found earlier
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 11

    A pharmacy makes 2 dm³ of antiseptic solution containing 30 g of dissolved solid.

    1. (a)

      Work out the concentration of the antiseptic in g/dm³.

      [2]
    2. (b)

      Calculate the mass of solid needed for 150 cm³ of the same solution.

      [2]
    3. (c)

      State how the concentration changes if the 30 g is made up to 3 dm³ instead.

      [1]
  2. 12

    A class performs titrations of hydrochloric acid against 25.0 cm³ portions of sodium hydroxide solution.

    Burette readings

    RunFinal / cm³Initial / cm³Titre / cm³
    Rough24.500.0024.50
    148.2024.5023.70
    223.850.1023.75
    347.5023.8523.65
    1. (a)

      Complete the titre column and identify the concordant runs.

      [2]
    2. (b)

      Calculate the mean titre.

      [2]
    3. (c)

      State the uncertainty of one burette reading and explain why the mean is trusted more than a single titre.

      [3]
  3. 13

    A student titrates 25.0 cm³ of potassium hydroxide solution with 0.20 mol/dm³ nitric acid. The mean titre is 18.0 cm³. (KOH + HNO₃ → KNO₃ + H₂O. K 39, O 16, H 1, N 14.) [Chemistry only]

    1. (a)

      Calculate the moles of nitric acid run in.

      [2]
    2. (b)

      Deduce the moles of KOH in the flask and its concentration in mol/dm³.

      [3]
    3. (c)

      Express the KOH concentration in g/dm³ (Mr 56).

      [2]
    4. (d)

      State why the student would not use this titration mixture to make potassium nitrate crystals directly.

      [1]

— End of paper —