Chemical Analysis

• The boiling or melting point tells you how pure a substance is
• Impurities will lower the melting point
• A pure substance contains only one compound or element
• Formulations are mixtures of two or more substances that are designed to have a specific function.
• Chromatography uses two phases, the mobile phase and the stationary phase.
• Chemicals that spend more time in the mobile phase move further
• Chlorine is tested for by using damp litmus paper
• If Chlorine is present, the litmus paper is bleached
• Oxygen is tested for by using a glowing splint
• If oxygen is present, the splint will relight
• Carbon Dioxide is tested for by bubbling it through limewater
• Limewater will turn cloudy if Carbon Dioxide is present
• Hydrogen is tested for using a lit splint
• If Hydrogen is present, you will hear a squeaky pop
• Sulphates are tested for using barium chloride and dilute hydrochloric acid
• If a sulphate is present, a white precipitate is formed
• Halides are tested for with silver nitrate and nitric acid
• Chloride gives a white precipitate
• Bromide gives a cream precipitate
• Iodide gives a yellow precipitate
• Lithium Ions burn with a crimson flame
• Sodium Ions burn with an yellow flame
• Potassium Ions burn with a lilac flame
• Calcium Ions burn with a green flame
• Calcium Ions burn with an orange-red flame
• Some metals form precipitates with sodium hydroxide
• Calcium forms a white precipitate
• Copper(II) forms a blue precipitate
• Iron(II) forms a green precipitate
• Iron(III) forms a brown precipitate
• Aluminium forms a white precipitate but if redissolves to a colourless solution if excess sodium hydroxide is added
• Magnesium forms a white precipitate
• During flame emission spectroscopy, each ion gives a characteristic line spectrum
• Flame Emission Spectroscopy is useful for mixtures
• Chemists use instrumental analysis using machines
• Advantages of Instrumental Analysis is it is very fast and accurate