Contents
Independent final check
Explain without the key
describe / calculate
Final check
(a) Describe what is meant by the relative atomic mass, Ar, of an element. (b) In a sample of potassium, 93 % of the atoms are potassium-39 and 7 % are potassium-41. Calculate the relative atomic mass of potassium. Give your answer to one decimal place.
describe: give the features or what happens. calculate: work out the answer from the data.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
Relative masses (3.2 Core 1–3): relative atomic mass as the average mass of the isotopes of an element compared to 1/12 of the mass of an atom of carbon-12, relative molecular mass and relative formula mass as the sum of the relative atomic masses, and reacting masses in simple proportions, without the mole. The mole and molar mass, calculating relative atomic mass from isotope abundances, percentage yield and purity are left to other modules.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus