Lesson 18C.1

18C.1 Deducing formulae from data Quiz: Pearson Edexcel Chemistry, Unit 18

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 18C.1, Deducing formulae from data: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 18: Organic Chemistry III, written with Revision Ninja.

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The 20 questions

  1. What products are formed when an organic compound is burnt completely in combustion analysis?

    • Carbon monoxide and hydrogen
    • Carbon and hydrogen chloride
    • Oxygen and ammonia
    • Carbon dioxide and water

  2. Which technique gives the molecular ion peak used to find the molecular formula from an empirical formula?

    • Thin-layer chromatography
    • Titration with sodium hydroxide
    • Infrared spectroscopy
    • Mass spectrometry

  3. A combustion of an organic compound produces 0.440 g of CO2. How many moles of carbon were in the sample?

    • 0.0100 mol
    • 0.0050 mol
    • 0.440 mol
    • 0.0200 mol

  4. The same combustion produces 0.180 g of H2O. How many moles of hydrogen atoms were in the sample?

    • 0.180 mol
    • 0.0400 mol
    • 0.0100 mol
    • 0.0200 mol

  5. A compound is 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. What is its empirical formula?

    • C2H4O2
    • CH2O
    • C3H6O3
    • CH4O

  6. A compound has an empirical formula CH2O and a relative molecular mass of 60. What is its molecular formula?

    • C3H8O
    • C2H4O2
    • C4H8O
    • CH2O

  7. A compound gives an orange precipitate with 2,4-DNPH but does not react with Tollens' reagent. What is it most likely to be?

    • A carboxylic acid
    • An alkene
    • A ketone
    • An aldehyde

  8. A hydrocarbon has an empirical formula C2H5 and a relative molecular mass of 58. What is its molecular formula?

    • C4H10
    • C3H8
    • C2H5
    • C6H15

  9. What is the percentage by mass of oxygen in a compound that is 52.2% carbon and 13.0% hydrogen, by difference?

    • 65.2%
    • 34.8%
    • 13.0%
    • 47.8%

  10. A compound is 52.2% C, 13.0% H and 34.8% O. What is its empirical formula?

    • C3H8O
    • CH3O
    • C4H12O2
    • C2H6O

  11. Why are combustion masses divided by molar masses in empirical formula calculations?

    • To convert masses into moles, so the mole ratio of each element can be found
    • To find the molar mass of the compound directly from the masses of carbon and hydrogen in the sample
    • To convert moles of gas into volume at room temperature only, so the gas can be measured in a syringe
    • To find the boiling point of the compound from the masses of each element, using a standard table

  12. A student says the empirical formula is always the molecular formula. Which evaluation is best?

    • Incorrect, since the empirical formula always has more atoms than the molecular formula does in every case
    • Correct, since the empirical formula always gives the true molecular mass of the compound under all conditions
    • Correct, since all molecules have the same number of atoms as their empirical formula in every case
    • Incorrect, since the molecular formula is a whole-number multiple of the empirical formula, which may be larger

  13. A compound has empirical formula C2H4O and relative molecular mass 88. What is its molecular formula?

    • C4H10O2
    • C3H6O2
    • C2H4O
    • C4H8O2

  14. Which combination of data is needed to deduce the structural formula of an unknown organic compound?

    • Only the mass of carbon dioxide produced in combustion, which gives the full structure directly
    • Only the boiling temperature and colour of the compound, which are enough to identify its structure
    • Only the melting temperature and density of the compound, which fix its structure uniquely
    • Molecular formula, functional group tests, and spectra such as IR and NMR

  15. Which spectroscopic technique shows the presence of a C=O group by a strong absorption near 1700 cm-1?

    • Infrared (IR) spectroscopy
    • 13C NMR spectroscopy, which counts the carbon environments
    • Chromatography, which separates the components
    • Mass spectrometry, which measures the molar mass

  16. A compound has a molecular ion at m/z 88 and a 1H NMR spectrum with two singlets in the ratio 3:1. Which information is most useful in deducing its structure?

    • The colour of the compound and its density at room temperature, which give clues about its functional groups directly
    • The molecular mass of 88 combined with the 3:1 ratio of equivalent proton environments
    • The melting temperature alone, which fixes the structure uniquely without any need for other spectroscopic data
    • The number of peaks in the infrared spectrum only, which identifies every bond type in the molecule uniquely

  17. What is the empirical formula of a compound with 0.0120 mol C and 0.0240 mol H?

    • CH3
    • CH
    • CH2
    • C2H

  18. Which gas is produced when a compound containing only C, H and O is burnt completely?

    • Sulfur dioxide
    • Carbon dioxide
    • Carbon monoxide
    • Hydrogen

  19. A compound with empirical formula CH2O has an unknown molecular ion. Which molecular mass gives C2H4O2?

    • 120
    • 30
    • 90
    • 60

  20. A compound contains 0.60 g C, 0.10 g H and 0.80 g O. What is its empirical formula?

    • C2H4O
    • CH4O2
    • CH2O
    • CH3O

All Pearson Edexcel Chemistry quizzes