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CAIE IGCSE Chemistry 3.3.7 Empirical formulae & molecular

Practise deriving empirical and molecular formulae from percentage composition, masses, mole ratios and relative molecular mass.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • divide masses or percentages by Ar values, then reduce to the simplest whole-number ratio
  • use empirical formula mass and Mr to scale up to the molecular formula
  • determine x in hydrated salts by comparing moles of anhydrous salt and H2O

3.3.7—Empirical formulae and molecular question 1

[Maximum number: 2]

Fluorine is a Group VII element. Fluorine forms compounds with metals and non-metals.

Tetrafluoroethene is an unsaturated compound with the formula C2 F4\mathrm{C}_{2} \mathrm{~F}_{4}. Tetrafluoroethene is the monomer used to make the polymer poly(tetrafluoroethene).

Deduce the empirical formula of:
tetrafluoroethene
poly(tetrafluoroethene).

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