CAIE A Level Chemistry 9701 · Group 17
The elements chlorine, bromine and iodine exist as diatomic molecules at room temperature. The table below shows their boiling points.
| Element | Boiling point / °C |
|---|---|
| Chlorine | –34 |
| Bromine | 59 |
| Iodine | 184 |
(a) State the colour of each halogen at room temperature. (b) Describe and explain the trend in volatility of the halogens shown by these data. (c) Describe and explain the trend in the bond strength of the diatomic molecules.
7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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