Chemical analysis

• What is a pure substance?

  A single element or compound not mixed with any other substance
• What is a formulation and how is it made?

  A mixture of compounds in measured quantities that has been designed as a useful product

  Formulations include fuels, cleaning agents, paints, medicines, alloys
• Describe the tests for hydrogen, oxygen, carbon dioxide and chlorine:

  Hydrogen: pop with burning splint over gas

  Oxygen: glowing splint relights

  Carbon dioxide: turns limewater milky

  Chlorine: bleaches damp litmus paper
• Describe the flame test results:

  Lithium compounds: crimson red flame

  Sodium compounds: yellow flame

  Potassium compounds: lilac flame

  Calcium compounds: orange red flame

  Copper compounds: green flame
• Describe the test for carbonate anions:

  Add dilute acid, e.g HCl

  Fizzing observed as CO2 is released
• Describe the test for sulfate anions:

  Add a solution containing Ba 2+ cations, e.g a solution of BaCl2

  White precipitate of BaSO4 forms
• Describe silver nitrate tests:

  Add a solution of AgNO3

  Chlorides: white precipitate

  Bromides: cream precipitate

  Iodides: yellow precipitate
• What are instrumental methods?

  They are accurate, sensitive and rapid methods which are very useful when the amount of sample is very small
• Describe the flame emission spectroscopy:

  > Instrumental method used for identifying metal ions in solution or measuring their concentration

  Spectroscope measured wavelength of light emitted by a metal ion

  > That allows for definite identification: sometimes colours are difficult to distinguish

  > Concentrations are found by measuring the intensity of light emitted

  -> The more intense light, the greater the concentration of the metal ions in a solution