Displacement reactions can be used to determine the relative reactivity of the halogen elements
This demonstration by Nigel Baldwin on YouTube shows the reactions between chlorine, bromine and iodine ions with potassium chloride, potassium bromide and potassium iodide respectively. You will see a colour change where a reaction has occurred. The reactivity trend of these three halogens can be deduced from the reactions that take place.
Mr Baldwin has produced clear colour changes for the purposes of filming by using higher concentrations of solutions than would be appropriate in the classroom. If students are going to carry this practical out in a school laboratory then CLEAPSS suggests that 0.002M bromine water is suitable for halogen/halide displacements. Solutions should also be decanted into smaller bottles for better handling to avoid spillages.
Also check out
- Reactions of halogens (as aqueous solutions) – a method for carrying out this practical in the classroom in association with the Nuffield Foundation.
- How to teach displacement reactions – an Education in Chemistry article relating to the displacement reactions of metals.
- Reactivity and displacement reactions – activities to engage students learning about reactivity trends, including reactivity trend snap.
We have collated these videos of key practical experiments to support remote teaching as part of our response to Covid-19. Teachers requested resources to help them deliver practical content without access to laboratories or equipment. We are developing further resources and welcome feedback to help us produce those you most need. Please email us or use the comment section below.
Practical videos | 14–16 students
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Practical videos: displacement reactions