CAIE A Level Chemistry 9701 · Reaction kinetics
A student adds 50 cm³ of dilute hydrochloric acid to 50 cm³ of sodium thiosulfate solution in a conical flask and measures the time for the mixture to become cloudy. In a second experiment, the student repeats the procedure but first dilutes the sodium thiosulfate solution by adding 50 cm³ of distilled water to it before mixing with the acid.
Compare the rate of reaction in the two experiments, and explain the difference in terms of the frequency of effective collisions.
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.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.