CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry: describe question

Describe5 marksChallenge

Hydrochloric acid reacts with sodium hydroxide as shown.

\ce{HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l)}

A student mixes 20.0 $\text{cm}^3$ of 2.00 $\text{mol dm}^{-3}$ hydrochloric acid with 40.0 $\text{cm}^3$ of 1.50 $\text{mol dm}^{-3}$ sodium hydroxide.

Describe how the student uses the mole concept to determine which reagent is in excess.

How this question is marked

5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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