CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry
An element, E, has two naturally occurring isotopes. Samples of E taken from two different rock deposits give slightly different relative atomic masses.
Suggest, in terms of the definitions of the unified atomic mass unit, relative isotopic mass and relative atomic mass, why the relative atomic mass can differ for different samples of the same element.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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