CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry
Water has the formula . Its relative molecular mass, Mr, is 18.
Explain what is meant by the unified atomic mass unit, by the relative atomic mass of an element, and by the relative molecular mass of a molecule. Use water to explain how the relative molecular mass of a molecule is related to the relative atomic masses of its atoms.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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