Description

A solution of ammonia is poured into each of three beakers which contain (unknown to the audience) a little phenolphthalein, a little lead nitrate solution and a little copper sulphate solution respectively, Pouring the contents of the beakers into acid reverses the changes to give a colourless solution.


Apparatus

Three 250cm beakers.

Two identical flasks of about 500cm capacity.

Three teat pipettes.

Chemicals
The quantities given are for one demonstration.

About 250cm of 1 mol dm ammonia solution. (To make 1
dm of 1 mol dm ammonia solution, make 57 cm of 880 ammonia solution up to 1 dm with deionized water.)

About 250cm of 2 mol dm nitric acid. (To make 1 dm of
2 mol dm nitric acid, make 125cm of concentrated (70%) nitric acid up to 1 dm with deionized water.)

About 1cm of approximately 0.5 mol dm copper sulphate. (Add about 2.5g of copper sulphate-5-water to 10 cm of deionized water.)

About 1cm of saturated lead nitrate solution. (Add 14g of lead nitrate to 10 cm of deionized water to make a saturated solution.)

About 1cm of phenolphthalein solution. (This is made by dissolving 1g of phenolphthalein solution in 600cm of ethanol and making it up to 1 dm with deionized water.)

Ensure that all the solutions are made up using deionized water otherwise the lead-containing solutions will be cloudy due to the formation of lead chloride from chloride ions in tap water.