Displacement reactions involving the halogens
3 marks · EasyA student added samples of chlorine, bromine and iodine solutions to three separate solutions of potassium chloride, potassium bromide and potassium iodide. The table shows her results:
| Halogen solution added | Potassium chloride | Potassium bromide | Potassium iodide |
|---|---|---|---|
| Chlorine | - | orange | brown |
| Bromine | - | - | brown |
| Iodine | - | - | - |
Which solution gave a brown colour when iodine was present? Name the halogen displaced.
Which is the most reactive halogen in this experiment? Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Potassium iodide with either chlorine or bromine solution; iodide is displaced.
(b) Chlorine is most reactive because it displaced bromide and iodide ions, while the others could not displace as many.
Common mistakes: Mixing up which halogen is most reactive
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · One mark for correct identification: potassium iodide with chlorine or bromine solution; displaced halogen: iodine.
M1 (b) · 1 mark · States chlorine is most reactive.
B2 (b) · 1 mark · Explains that chlorine displaced bromide and iodide but the others did not.
Worked solution
a) Potassium iodide with either chlorine or bromine turns brown. Iodide is displaced (iodine forms).
b) Chlorine is most reactive. It is able to displace both bromide and iodide, while bromine only displaces iodide, and iodine does not displace any.