Revision NotesExam QuestionsPast Papers
O LevelChemistryCambridgeExam Questions3. Stoichiometry3.3 The Mole & the Avogadro Constant

The Mole & the Avogadro Constant (Cambridge O Level Chemistry)

Exam Questions

5 hours50 questions

Select a question set to download for
3.3 The Mole & the Avogadro Constant

Select an answer set to view for
3.3 The Mole & the Avogadro Constant

Easy
Medium
Hard
11 mark

Which row correctly describes the mole and the value of Avogadro’s constant?

 

one mole of a substance is equal to

 one mole of a substance contains
A the substances relative atomic or molecular mass in grams 6.02 x 1023 atoms, molecules or formula units
B the substances atomic number in grams 12.02 x 1023 atoms, molecules or formula units
C the substances relative atomic or molecular mass in grams 6.02 x 1022 atoms, molecules or formula units
D the substances atomic number in grams 12.02 x 1023 atoms, molecules or formula units

    Choose your answer

    Did this page help you?

    21 mark

    The complete combustion of methane produces carbon dioxide and steam.

    CH4(g) + 2 O2(g) → 2 H2O(g) + CO2(g)

    Which statements are about the reaction correct?

    1 The empirical formula of methane is CH4
    2 The number of atoms in 1 mole of methane is 4 x Avogadro’s constant
    3 1 mole of methane produces 72 dm3 of gaseous products at r.t.p
    4 1 mole of methane occupies a volume of 12 dm3 at r.t.p

    • 1, 2 and 3

    • 1 and 2

    • 1 and 3

    • 2 and 4

    Choose your answer

    Did this page help you?

    31 mark

    Magnesium carbonate and hydrochloric acid react to produce salt, water and carbon dioxide.

    MgCO3 (s) + 2HCl (aq) → MgCl2 (aq) + H2O (l) + CO2 (g) 

    What is the volume of CO2 produced when 21 g of magnesium carbonate (Mr = 84) reacts completely with excess hydrochloric acid?

    One mole of gas occupies 24.0 dm3 at room temperature and pressure.

    • 4 dm3

    • 8 dm3

    • 6 dm3

    • 2 dm3

    Choose your answer

    Did this page help you?

    41 mark

    Calcium carbonate undergoes thermal decomposition at high temperatures to form calcium oxide and carbon dioxide.

    CaCO3 → CaO + CO2

    What mass of calcium oxide (Mr = 56) is formed when 60 g of calcium carbonate (Mr = 100) is completely decomposed?

    • 28 g

    • 18.5 g

    • 60 g

    • 33.6 g

    Choose your answer

    Did this page help you?

    11 mark

    What is the concentration in mol dm-3 of a solution of sodium hydroxide that contains 16 g of NaOH in 200 cm3 of distilled water?

    • 2 mol dm-3

    • 2.5 mol cm-3

    • 0.2 mol dm-3

    • 1 mol cm-3

    Choose your answer

    Did this page help you?

    21 mark

    A student was given a sample of hydrochloric acid and asked to find its concentration in mol / dm3. She titrated 25 cm3 of the acid against a standard solution of sodium hydroxide of 0.1 mol dm-3. The average titre of sodium hydroxide was 30 cm3.

    What is the concentration of the acid?

    • 0.50 mol dm-3

    • 0.12 mol dm-3

    • 1.25 mol dm-3

    • 1.0 mol dm-3

    Choose your answer

    Did this page help you?

    31 mark

    A student thermally decomposes 24.8 g of copper carbonate and obtains 11.2 g of copper(II) oxide and carbon dioxide gas which is released.

    CuCO3 → CuO + CO2

    What is the percentage yield of CuO?

    • 55 %

    • 70 %

    • 82 %

    • 90 %

    Choose your answer

    Did this page help you?

    41 mark

    A sample of chalk (limestone) with a mass of 1.70 g was reacted with excess HCl and the amount of carbon dioxide given off was measured using a gas syringe. 0.36 dm3 of CO2 gas was collected at r.t.p.

    CaCO3 + 2HCl → CaCl2 + CO2 + H2O

    What is the percentage purity of the chalk?

    • 75 %

    • 88 %

    • 90 %

    • 98 %

    Choose your answer

    Did this page help you?

    51 mark

    A chemist wants to make calcium nitrate. They start with 8.00 g of pure calcium oxide and an excess of dilute nitric acid. They produce 12.65 g of pure, dry anhydrous calcium nitrate crystals.

    What is the percentage yield of calcium nitrate?

    [relative atomic masses, Ar: Ca, 40; N, 14; H, 1; O, 16]

    • 54.0

    • 63.2

    • 67.1

    • 86.8

    Choose your answer

    Did this page help you?

    61 mark

    The relative formula masses of four compounds are given.

    A student has a 1.0 g sample of each compound.

    Which sample contains the highest number of moles of oxygen atoms?

     

    compound

    relative formula mass

    A

    Al2O3

    102

    B

    CuO

    80

    C

    H2SO4

    98

    D

    HNO3

    63

      Choose your answer

      Did this page help you?

      71 mark

      A compound contains 70% by mass of iron and 30% by mass of oxygen.

      What is its empirical formula? [Ar: O, 16; Fe, 56]

      • FeO

      • Fe2O3

      • Fe3O2

      • Fe3O4

      Choose your answer

      Did this page help you?

      81 mark

      25.0 g of hydrated copper(II) sulfate crystals are heated to produce anhydrous copper(II) sulfate and water.

      CuSO4•5H2O(s) → CuSO4(s) + 5H2O(g)

      What is the mass of anhydrous copper(II) sulfate formed?

      [Mr: CuSO4, 160; H2O, 18]

      • 9.0 g

      • 16.0 g

      • 22.5 g

      • 25.0 g

      Choose your answer

      Did this page help you?

      91 mark

      The relative formula masses of four compounds are given.

      A student has a 1.0 g sample of each compound.

      Which sample contains the highest number of moles of oxygen atoms?

       

       

      compound

      relative formula mass

      A

      Al2O3

      102

      B

      CuO

      80

      C

      H2SO4

      98

      D

      HNO3

      63

        Choose your answer

        Did this page help you?

        101 mark

        50.0 cm3 of 0.10 mol/dm3 silver nitrate, AgNO3, is added to 150.0 cm3 of 0.05 mol/dm3 sodium iodide, NaI, in a beaker.

        After the reaction, solid silver iodide is present in the beaker.

        What else is present?

        • aqueous silver nitrate and aqueous sodium nitrate

        • aqueous sodium iodide and aqueous sodium nitrate

        • aqueous sodium iodide only

        • aqueous sodium nitrate only

        Choose your answer

        Did this page help you?

        111 mark

        When 0.1 mol of the hydrocarbon, C5H12, is completely combusted it produces carbon dioxide, CO2, and water, H2O.

        C5H12(l) + 8O2(g) → 5CO2(g) + 6H2O(g)

        What is the volume of carbon dioxide produced when measured at room temperature and pressure?

        • 0.5 dm3

        • 2.4 dm3

        • 5.0 dm3

        • 12 dm3

        Choose your answer

        Did this page help you?

        121 mark

        Which compound has the lowest percentage by mass of nitrogen?

        • (NH2)2CO [Mr: 60]

        • (NH4)2SO4 [Mr: 132]

        • (NH4)3PO4 [Mr: 149]

        • NH4NO3 [Mr: 80]

        Choose your answer

        Did this page help you?

        11 mark

        Calcium carbide and water react to produce ethyne and calcium hydroxide.

        CaC2 (s) + 2H2O (l) → C2H2 (g) + Ca(OH)2 (s)

        What is the volume of C2H2 produced, at standard temperature and pressure, when 45 g of water reacts completely with calcium carbide?

        • 72 dm3

        • 30 dm3

        • 24 dm3

        • 6 dm3

        Choose your answer

        Did this page help you?

        21 mark

        Aluminium and oxygen react to produce aluminium oxide.

        4 Al + 3 O2 → 2 Al2O3

        How many kilograms of aluminium oxide are formed when 5.4 kg of aluminium react with excess oxygen?

        • 5.4 kg

        • 88 kg

        • 10.2 kg

        • 33.6 kg

        Choose your answer

        Did this page help you?

        31 mark

        Magnesium nitride and water react to produce a precipitate of magnesium hydroxide and ammonia gas.

        Mg3N2 + 6 H2O → 3 Mg(OH)2 + 2 NH3

        How much magnesium nitride is needed to produce 87 g of the precipitate in excess water?

        • 24 g

        • 50 g

        • 30 g

        • 12 g

        Choose your answer

        Did this page help you?

        41 mark

        A student was asked to find the concentration in g / dm3 of a solution of sulfuric acid. She transferred 25 cm3 of the acid to a 250 cm3 volumetric flask and made it up to the mark. She titrated 25 cm3 of the diluted acid against a standard solution of sodium hydroxide of 0.1 mol dm-3. The average titre of sodium hydroxide was 18 cm3.

        What is the concentration of the original acid in grams per decimetre?

        • 9.85 g dm-3

        • 12.25 g dm-3

        • 98 g dm-3

        • 35.28 g dm-3

        Choose your answer

        Did this page help you?

        51 mark

        A chemist reacted 0.6 g of magnesium with 0.6 dm3 of oxygen in a sealed container to produce magnesium oxide.

        2Mg + O2 → 2MgO

        Which row correctly describes the limiting reactant?

          limiting reactant reason
        A Mg in excess
        B Mg is used up first
        C O2 is used up first
        D O2 in excess

          Choose your answer

          Did this page help you?