Group 17: Question 7
Syllabus 11.1, 11.2, 11.3, 11.4
A technician prepares three test-tubes of freshly made aqueous halogen solutions: chlorine water, bromine water and iodine solution.
Which row correctly gives the colour of each solution?
| Chlorine water | Bromine water | Iodine solution | |
|---|---|---|---|
| A | pale green | orange | brown |
| B | colourless | red-brown | purple |
| C | yellow | brown | orange |
| D | pale green | purple | orange |
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Worked solution
Step 1: Recall the colours of the halogens as aqueous solutions
When dissolved in water, the three common halogens give solutions of the following characteristic colours:
- Chlorine water ( dissolved in water): pale green (a faint tinge, close to colourless).
- Bromine water ( dissolved in water): orange.
- Iodine solution ( dissolved in water): brown.
Step 2: Match this to row A
Row A gives pale green (chlorine water), orange (bromine water), and brown (iodine solution), exactly matching the recalled colours.
Why the other options are wrong
- B: “colourless” understates chlorine water’s pale green tinge; “red-brown” describes pure liquid bromine rather than dilute bromine water; “purple” describes iodine dissolved in a non-polar organic solvent (such as cyclohexane), not iodine’s aqueous solution, which is brown.
- C: the colours given (yellow, brown, orange) do not correctly match any of the three aqueous solutions in the right places. Bromine water is not brown, and iodine solution is not orange.
- D: bromine water and iodine solution have been swapped. Bromine water is orange, not purple, and iodine solution is brown, not orange.
Final answer
- Chlorine water is pale green, bromine water is orange, and iodine solution is brown, option A.