A student mixes three pairs of solutions and records the colours.
| Mixture | Colour of halogen solution before mixing | Colour after mixing |
|---|---|---|
| 1: chlorine water + potassium bromide | very pale green | orange |
| 2: iodine solution + potassium bromide | brown | brown |
| 3: bromine water + potassium iodide | orange | brown |
The student concludes that a displacement reaction happened in all three mixtures because each mixture is coloured at the end.
Which evaluation of this conclusion is correct?
The conclusion is correct, because every final mixture contains a coloured halogen
Only mixture 1 reacted, because the brown colour in mixture 3 is unreacted bromine
Mixtures 2 and 3 reacted, because both of them contain brown iodine at the end
Mixtures 1 and 3 reacted, because the brown in mixture 2 is the iodine that was added
106 exam-style questions on Edexcel GCSE Chemistry 7.2 Group 7, covering 7.2.1 Physical properties of the halogens, 7.2.2 Reactions of the halogens, 7.2.3 Relative reactivity and displacement reactions of the halogens, and 7.2.4 Halogen displacement as a redox reaction. Each one has a worked solution and a mark scheme showing where the marks go.