CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry: explain question

Explain4 marksStandard

The Avogadro constant, $L$ , is $6.02 \times 10^{23}\ \text{mol}^{-1}$ . One atom of carbon-12 has a mass of exactly 12 atomic mass units (u), where $1\ \text{u} = 1.66 \times 10^{-24}\ \text{g}$ . Explain what is meant by one mole of carbon-12 atoms in terms of $L$ , and use this to explain why the mass of one mole of carbon-12 atoms is 12 g.

How this question is marked

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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