Analysing Substances
Metal ions can be identified using flame tests. In flame tests:
Lithium burns with a crimson flame
Sodium burns with a yellow flame
Potassium burns with a lilac flame
Calcium burns with a brick red flame
Barium burns with an apple green flame.
When it is reacted with sodium hydroxide solution:
Aluminium forms a white precipitate -- this dissolves in excess sodium hydroxide solution
Calcium forms a white precipitate -- this does not dissolve in excess sodium hydroxide solution
Magnesium forms a white precipitate -- this does not dissolve in excess sodium hydroxide solution
Copper (II) forms a blue precipitate
Iron (II) forms a green precipitate
Iron (III) forms a brown precipitate.
When it is reacted with silver nitrate solution in the presence of dilute nitric acid:
Silver chloride forms a white precipitate
Silver bromide forms a cream precipitate
Silver iodide forms a yellow precipitate.
(Silver chloride, silver bromide and silver iodide are all examples of halide ions.)
When they are reacted with barium chloride solution in the presence of dilute hydrochloric acid:
Sulphate ions in solution form a white precipitate.
When they are reacted with dilute acids:
Carbonates form carbon dioxide.
When it is reacted with limewater:
Carbon dioxide forms a white precipitate -- this turns the limewater cloudy.
We can measure the volumes of acid and alkali solutions that react with each other using titration and a suitable indicator. If the concentration of one of the reactants is known, we can use the results of a titration to find the concentration of the other reactant.
