The aim of this experiment is to find the effect of varying temperature on the rate of reaction between sodium thiosulphate solution and hydrochloric acid.
Initially the reaction mixture is clear but gradually becomes cloudy as solid sulphur is formed in the reaction. We can follow the course of the reaction by placing the reaction mixture over a cross drawn on a piece of paper and timing how long it takes for the cross to be obscured by the sulphur.
This experiment produces toxic suphur dioxide which can be a particular problem for asthmatics – a safer method is to use a microscale version. Thiosulphate / acid reaction – microscale
Effect of Temperature on Reaction Rate – Pupil
