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Chapter 5 Practice Paper: The Mole Concept and Stoichiometry — question paper

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QQ/S3CH/CH5

Secondary 3 · Chemistry (G2 / G3)

Chapter 5 Practice Paper

The Mole Concept and Stoichiometry

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Chemical equations should be balanced, with state symbols shown where the question asks for them.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is shown on its cover.

Original practice material written for the MOE Chemistry syllabus. It is not an official MOE or school examination paper. Chapter 5 (formula masses, moles, concentrations, gas volumes, reacting masses, limiting reagents).

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

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    The relative formula mass of Mg(NO₃)₂ (Mg = 24, N = 14, O = 16) is

    1. A124
    2. B148
    3. C164
    4. D62
    ( )
  2. 2

    The number of moles in 8.0 g of oxygen gas, O₂ (Mr = 32), is

    1. A0.125 mol
    2. B0.50 mol
    3. C2.0 mol
    4. D0.25 mol
    ( )
  3. 3

    The volume at r.t.p. of 2.0 mol of methane is

    1. A48 dm³
    2. B24 dm³
    3. C12 dm³
    4. D4.8 dm³
    ( )
  4. 4

    A solution of copper(II) sulfate is 0.25 mol/dm³ (CuSO₄ = 80). Its concentration in g/dm³ is

    1. A320 g/dm³
    2. B40 g/dm³
    3. C20 g/dm³
    4. D80 g/dm³
    ( )
  5. 5

    6.0 g of magnesium (Ar = 24) burns in excess oxygen. The mass of magnesium oxide formed (2Mg + O₂ → 2MgO, MgO = 40) is

    1. A6.0 g
    2. B10 g
    3. C20 g
    4. D40 g
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Show your working; give numerical answers to 3 significant figures where appropriate, with units.

  1. 1

    Ammonium nitrate, NH₄NO₃, is a nitrogen-rich fertiliser (H = 1, N = 14, O = 16).

    1. (a)

      Calculate the relative formula mass of NH₄NO₃.

      [1]
    2. (b)

      Calculate the percentage by mass of nitrogen in ammonium nitrate.

      [2]
    3. (c)

      A farmer spreads 500 g of the fertiliser. What mass of nitrogen does it contain?

      [1]
  2. 2

    25.0 cm³ of sodium hydroxide solution is neutralised by 20.0 cm³ of 0.0500 mol/dm³ sulfuric acid: H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O.

    1. (a)

      Calculate the moles of sulfuric acid used.

      [1]
    2. (b)

      Calculate the moles of sodium hydroxide neutralised.

      [1]
    3. (c)

      Calculate the concentration of the sodium hydroxide in mol/dm³.

      [2]
    4. (d)

      Express this concentration in g/dm³ (NaOH = 40).

      [2]
  3. 3

    6.5 g of zinc (Ar = 65) is added to excess dilute hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂. The gas is collected at r.t.p. (molar volume 24 dm³).

    1. (a)

      Calculate the moles of zinc used.

      [1]
    2. (b)

      Calculate the volume of hydrogen collected.

      [2]
    3. (c)

      Calculate the mass of zinc chloride formed (ZnCl₂ = 136).

      [2]
  4. 4

    1.4 g of nitrogen (Ar = 14) combines exactly with 3.2 g of oxygen (Ar = 16). The molecular Mr of the oxide formed is 46.

    1. (a)

      Calculate the moles of nitrogen and of oxygen that combine.

      [2]
    2. (b)

      Deduce the empirical formula of the oxide.

      [2]
    3. (c)

      State the molecular formula, with a reason.

      [1]

— End of paper —