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Chapter 6 Practice Paper: The mole and reacting masses — question paper

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

Chapter 6 Practice Paper

The mole and reacting masses

Duration: 40 minutes
Total: 30 marks
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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.
  • Relative atomic masses (Ar): H 1, C 12, N 14, O 16, Mg 24, S 32, Cl 35.5, Ca 40, Fe 56, Cu 64.
  • Molar gas volume at RTP = 24 dm³.
  • 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 6: the mole and Avogadro constant, mol = mass ÷ Mr, equations as mole recipes, reacting masses, limiting reactants, molar gas volume (Chemistry-only, Higher).

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

    The Avogadro constant is the number of particles in

    1. Aone mole
    2. Bone relative formula mass
    3. Cone gram
    4. Done dm³ of gas at STP
    ( )
  2. 2

    The mass of 0.2 mol of calcium carbonate, CaCO₃ (Ca 40, C 12, O 16), is

    1. A8.8 g
    2. B20 g
    3. C44 g
    4. D100 g
    ( )
  3. 3

    How many moles are in 3.2 g of sulfur dioxide, SO₂ (S 32, O 16)?

    1. A0.5 mol
    2. B64 mol
    3. C0.05 mol
    4. D0.04 mol
    ( )
  4. 4

    In 3Fe + 2O₂ → Fe₃O₄, the moles of iron needed to make 4 mol of Fe₃O₄ are

    1. A12 mol
    2. B4 mol
    3. C6 mol
    4. D8 mol
    ( )
  5. 5

    A reaction vessel holds 1 mol of N₂ and 1 mol of H₂ (N₂ + 3H₂ → 2NH₃). The limiting reactant is

    1. Awhichever reacts faster
    2. Bhydrogen, because 1 mol of nitrogen would need 3 mol of hydrogen but only 1 mol is present
    3. Chydrogen, because its molecules are lighter
    4. Dneither, they match
    ( )
  6. 6

    At RTP, 0.1 mol of any gas occupies

    1. A24 dm³
    2. B240 cm³
    3. C12 dm³
    4. D2.4 dm³
    ( )
  7. 7

    Which mass of MgO (Mr 40) forms from 3.6 g of Mg with excess oxygen (2Mg + O₂ → 2MgO; Mg 24)?

    1. A2.4 g
    2. B9.6 g
    3. C6.0 g
    4. D3.6 g
    ( )
  8. 8

    The number of atoms in 0.5 mol of helium is

    1. A3.01 × 10²³
    2. B6.02 × 10²³
    3. C1.204 × 10²⁴
    4. D0.5 × 10²³
    ( )
  9. 9

    2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. From 0.4 mol of NaHCO₃, the moles of Na₂CO₃ formed are

    1. A0.1 mol
    2. B0.2 mol
    3. C0.4 mol
    4. D0.8 mol
    ( )
  10. 10

    CuO + H₂ → Cu + H₂O. Reducing 8.0 g of CuO (Cu 64, O 16) gives what mass of copper?

    1. A7.95 g
    2. B1.6 g
    3. C12.8 g
    4. D6.4 g
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 11

    A technician prepares a solution by dissolving 0.15 mol of copper sulfate (CuSO₄, Cu 64, S 32, O 16) in water.

    1. (a)

      Calculate the Mr of CuSO₄.

      [1]
    2. (b)

      Calculate the mass dissolved.

      [1]
    3. (c)

      Calculate the number of formula units in the beaker (to 3 significant figures).

      [1]
    4. (d)

      The technician actually needs 0.30 mol. State the mass that should have been weighed.

      [1]
    5. (e)

      State why doubling the moles doubles the mass.

      [1]
  2. 12

    Aluminium reacts with chlorine: 2Al + 3Cl₂ → 2AlCl₃ (Al 27, Cl 35.5).

    1. (a)

      A student burns 5.4 g of aluminium in excess chlorine. Calculate the mass of AlCl₃ formed (Mr 133.5).

      [3]
    2. (b)

      Calculate the volume of chlorine used up at RTP.

      [2]
    3. (c)

      A second student has only 7.1 g of chlorine (0.1 mol) but plenty of aluminium. Calculate the mass of AlCl₃ they can make.

      [2]
  3. 13

    Limestone (pure calcium carbonate) is roasted in a kiln: CaCO₃ → CaO + CO₂ (Ca 40, C 12, O 16). A charge of 250 g of limestone is heated strongly.

    Kiln data

    QuantityValue
    Limestone charged250 g
    Molar volume at RTP24 dm³
    1. (a)

      Calculate the moles of CaCO₃ charged.

      [1]
    2. (b)

      Calculate the mass of CaO expected.

      [2]
    3. (c)

      Calculate the volume of CO₂ released at RTP if the reaction goes to completion.

      [2]
    4. (d)

      After firing, the solid residue actually weighs 154 g. Explain what this shows and calculate the percentage of limestone that decomposed.

      [3]

— End of paper —