Photo by C. Lloyd at SSERC (Public Domain)

The reaction between propanone and iodine is first order with respect to propanone and first order with respect to the hydrogen ions which catalyse the reaction.

The order with respect to iodine can be determined by taking a reaction mixture in which the initial concentrations of propanone and hydrogen ions are very much larger than that of iodine. With such conditions, only the concentration of the iodine will vary significantly during the reaction and this will allow us to see what effect it has on the reaction rate.

The course of the above reaction can be followed by monitoring the concentration of iodine This involves removing samples from the reaction mixture from time to time and analysing them for iodine.

Propanone-iodine reaction – pupil guide

Propanone-iodine reaction – Teacher’s guide

Propanone-iodine reaction – Risk assessment