Reactivity Trends (OCR GCSE Chemistry A (Gateway)) : Revision Note
Displacement Reactions
Displacement Reactions
Practical Skills Development
Safe use and careful handling of gases, liquids and solids, including:
Careful mixing of reagents under controlled conditions,
Using appropriate apparatus to explore chemical changes and/or products
Presenting observations and other data using appropriate formats
Aim
To use displacement reactions to identify the reactivity trend of Group 7 elements
Health & Safety Aspects

Cyclohexane is also highly flammable so should not be near open flames
Chlorine and bromine water are harmful so should be handled carefully and safety goggles worn
The fumes from chlorine and bromine are unpleasant so the reactions should be carried out in a well ventilated area or fume cupboard
Small volumes should be used to minimise the risk of these hazardous substances
Due to the hazards present this experiment is best carried out as a teacher demonstration
Materials
spotting or dimple tile
0.1% solutions of Cl2, Br2 and I2
0.1 mol / dm3 solutions of KCl, KBr and KI
cyclohexane, C6H12
Universal indicator paper
Method
Three drops of the halogens are added to separate wells in the dimple tile and the colours recorded
In a second set of wells, the same three halogen solutions are added separately, followed by three drops of potassium chloride
The procedure is repeated in a third and fourth set of wells using potassium bromide and potassium iodide , respectively
The colours of the resulting solutions are noted
The halogen colours are more easily seen if they are withdrawn in a pipette and added to a test tube containing 1-2 cm depth of cyclohexane and shaken
Finally, a piece of universal indicator is added, in turn, to each of the halogen solutions and the colour recorded
Record all observations in suitable tables
Results
The Colour of the Halogen Solutions

The Reactions of Halogens with Halide Ions

The Effect of Halogen Solutions on Indicator Paper

Conclusions
Chlorine appears to displace bromine and iodine from solutions of their compounds
Bromine displaces iodine from solutions of its compounds
A more reactive halogen displaces a less reactive one
The order of reactivity from this experiment is chlorine > bromine > iodine
Chlorine is a strong bleaching agent, bromine less so and iodine not at all
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?