Analysing Substances + Tests for Ions
Chemical analysis is useful e.g. blood tests - for monitoring general health and diagnosing diseases, also alcohol content of blood. Water companies - purity of the drinking water they provide.
Qualitative analysis tells you what is present (even a trace can be bad)
Quantitative analysis tells you how much is present
Test for Positive Ions using NaOH to give a coloured metal hydroxide precipitate
Add a few drops of NaOH to your solution to form a coloured insoluble hydroxide hopefully!
Calcium - White Copper(II) - Blue Iron (II) - Green Iron (III) - Brown
Aluminium - White. But then dissolves in excess NaOH to become colourless.
Ammonium - No precipate, but gives off amonia when heated. Amonia - damp universal indicator paper goes purple, red litmus paper goes blue, also smell: urine.
More Tests for Ions
Test for halides with dilute nitric acid then silver nitrate
Acid gets rid of carbonate ions before test. Iodide - yellow precipitate silver iodide.
Chloride - white precipitate silver chloride. Bromide - cream precipitate silver bromide.
Sodium - yellow/orange Potassium - lilac Calcium - brick red Copper - blue/green
Test for carbonates - any carbon dioxide?
Carbonate+acid=CO2 -bubble through limewater -milky? Then CO2 -was a carbonate.
Test for sulphates with dilute hydrochloric acid then barium chloride solution
If white precipitate of barium sulphate is formed then original compound was a sulphate.
Test for chlorides with dilute nitric acid then silver nitrate solution
If white precipitate of silver chloride is formed then original compound was a chloride.