Lesson 3.1.2.5

3.1.2.5 Balanced equations and associated calculations Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.2.5, Balanced equations and associated calculations: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. What is the formula for percentage atom economy?

    • (Mr of desired product / sum of Mr of all reactants) x 100
    • (actual mass of product / theoretical mass of product) x 100
    • (Mr of all reactants / Mr of the desired product) x 100
    • (Mr of desired product / Mr of the by-product only) x 100

  2. Which expression gives percentage yield?

    • (theoretical mass / actual mass) x 100
    • (Mr / moles) x 100
    • (mass of waste / total mass) x 100
    • (actual mass / theoretical mass) x 100

  3. In an ionic equation, what is a spectator ion?

    • An ion that takes no part in the reaction and appears unchanged on both sides
    • An ion that forms the precipitate in every reaction, so it is always removed from solution
    • An ion that is removed from the reaction as a solid only, leaving no trace in solution
    • An ion that is always a gas in the products and leaves the solution as a bubble

  4. In a balanced equation, what do the coefficients represent?

    • The molar ratio of reactants and products
    • The volume of gas produced at 1 atm only
    • The mass ratio of the products
    • The number of protons in each species

  5. Which set of coefficients balances the equation Al + O2 -> Al2O3?

    • 1, 1, 1
    • 3, 2, 4
    • 4, 3, 2
    • 2, 1, 1

  6. In the balanced equation C3H8 + O2 -> CO2 + H2O, what is the coefficient of O2?

    • 10
    • 3
    • 4
    • 5

  7. Which statement about percentage atom economy is correct?

    • Atom economy is always greater than 100% for addition reactions because of extra atoms
    • A high atom economy means the percentage yield is always high, so the reaction is efficient
    • Atom economy depends on the experimental yield, which is measured after each reaction
    • A high atom economy means more of the reactant mass ends up in the desired product

  8. Heating 10.0 g of calcium carbonate (Mr = 100) gives calcium oxide and carbon dioxide. What is the mass of carbon dioxide produced?

    • 5.6 g
    • 4.4 g
    • 10.0 g
    • 2.2 g

  9. What volume of hydrogen at room temperature and pressure (24.0 dm3 per mole) forms from 0.25 mol of magnesium reacting with excess hydrochloric acid?

    • 24.0 dm3
    • 0.25 dm3
    • 6.0 dm3
    • 12.0 dm3

  10. What is the percentage atom economy for making iron from Fe2O3 + 3CO -> 2Fe + 3CO2? (Mr: Fe2O3 = 160, CO = 28, Fe = 56)

    • 100%
    • 70.0%
    • 45.9%
    • 91.8%

  11. A reaction gives 5.00 g of product, but the theoretical yield is 6.25 g. What is the percentage yield?

    • 20.0%
    • 125%
    • 80.0%
    • 66.7%

  12. H2SO4 reacts with NaOH: H2SO4 + 2NaOH -> Na2SO4 + 2H2O. 25.0 cm3 of 0.100 mol dm-3 NaOH is used. How many moles of H2SO4 reacted?

    • 0.0025 mol
    • 0.00125 mol
    • 0.005 mol
    • 0.0500 mol

  13. 2.40 g of magnesium burns completely in oxygen to form magnesium oxide. What is the mass of magnesium oxide formed? (Ar: Mg = 24, O = 16)

    • 2.40 g
    • 6.40 g
    • 4.00 g
    • 3.20 g

  14. Zinc reacts with hydrochloric acid: Zn + 2HCl -> ZnCl2 + H2. What mass of hydrogen is formed from 6.5 g of zinc? (Ar: Zn = 65)

    • 0.1 g
    • 2.0 g
    • 0.2 g
    • 0.4 g

  15. Which balanced equation represents the complete combustion of methane?

    • CH4 + O2 -> CO2 + H2O
    • 2CH4 + O2 -> 2CO2 + H2O
    • CH4 + 2O2 -> CO + 2H2O
    • CH4 + 2O2 -> CO2 + 2H2O

  16. A 2.00 g tablet of calcium carbonate releases 0.60 g of carbon dioxide on complete reaction with excess acid. What is the percentage of calcium carbonate in the tablet? (Mr: CaCO3 = 100, CO2 = 44)

    • 30.0%
    • 100%
    • 80.0%
    • 68.2%

  17. A 5.00 g sample of hydrated magnesium sulfate, MgSO4.xH2O, leaves 2.45 g of anhydrous MgSO4 (Mr = 120) when heated. What is x? (Mr of water = 18)

    • 7
    • 8
    • 6
    • 5

  18. Which reaction type can, in principle, have an atom economy of 100%?

    • Addition reaction
    • Hydrolysis that forms a by-product
    • Substitution reaction
    • Elimination reaction

  19. 0.20 mol of Mg reacts with 0.30 mol of HCl: Mg + 2HCl -> MgCl2 + H2. What is the maximum amount of hydrogen formed in moles?

    • 0.10 mol
    • 0.15 mol
    • 0.30 mol
    • 0.20 mol

  20. 25.0 cm3 of 0.100 mol dm-3 HCl reacts exactly with sodium carbonate: Na2CO3 + 2HCl -> 2NaCl + H2O + CO2. What mass of Na2CO3 (Mr = 106) reacted?

    • 0.265 g
    • 0.0265 g
    • 0.1325 g
    • 0.0025 g

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