Solution X

Year 10 applied their knowledge of tests for anions and cations to discover the ions present in Solution X.

Solution X was a concoction of a metal salt solution, with other chemicals. It was a blue solution.

Test 1. 1 M sodium hydroxide solution was added to give a brown precipitate showing the presence of Iron (III)
Test 2. The addition of silver nitrate solution gave a white precipitate showing the presence of Chloride.
Test 3. Solution X turned blue litmus paper red: it was acidic and so contained Hydrogen ions
Test 4. Solution X was heated with aluminium foil and 1 M sodium hydroxide solution. The gas given off turned red litmus paper blue, because ammonia gas was released. Therefore the solution contained nitrate ions.

The class accomplished this fairy well, although surprisingly didn't all think to try test 3 given the starting equipment.

In the end every group identified the four ions and deduced I has mixed iron (III) chloride with nitric acid. However they couldn't account for the blue colour, perhaps because at IGCSE we don't learn how to test for blue food colouring