CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry: suggest question

Suggest6 marksChallenge

Acidified water was electrolysed using inert electrodes, and the hydrogen and oxygen produced were collected in graduated syringes at room temperature and pressure. In one run the volumes collected were 36.0 cm3 of hydrogen and 18.0 cm3 of oxygen. Suggest how the student could use these volumes, and further gas-volume measurements, to deduce the stoichiometric relationship for the decomposition of water. Suggest also why the volumes in a single run may not be exactly in the expected whole-number ratio from this relationship.

How this question is marked

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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