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An interesting introduction to the electrolysis of brine (sodium chloride solution). Students use Universal Indicator to help them follow what is happening during the reaction.
Apparatus and chemicals
Eye protection Each working group will require: U-shaped test tube Clamp and clamp stand Carbon electrodes and electrode holders, 2 of each Electrical leads, 2 Power pack Beaker (100 cm3) Spatula Stirring rod Students will need access to: Sodium chloride (salt) Universal indicator (Highly flammable) Distilled water
Health & Safety
Wear eye protection.
A. Before the demonstration, assemble the apparatus as shown in first diagram. Ensure that the connections to the boiling tubes are the correct way round.
B. Place a piece of blue cobalt chloride paper into the first boiling tube and half-fill the second boiling-tube with limewater.
C. At the start of the demonstration, turn on the pump so that a gentle stream of air is drawn through the apparatus.
D. Light the candle and leave for a few minutes until the cobalt chloride paper turns pink (from blue) and the limewater goes milky. This indicates the presence of water and carbon dioxide respectively.
This experiment has been reproduced from Practical Chemistry: http://practicalchemistry.org/experiments/identifying-the-products-of-combustion,43,EX.html
- 1 Filter pumps (http://www.practicalchemistry.org/standard-techniques/filtering,51,AR.html)
- 2 Make your own cobalt chloride paper (http://www.practicalchemistry.org/standardtechniques/preparing-and-using-cobalt-chloride-indicator-papers,43,AR.html)