Topic 8 - Chemical analysis

• What is a pure substance?

  A single element or compound
• How is a formulation defined?

  A mixture of compounds in measured quantities
• What are examples of formulations?

  • Fuels
  • Cleaning agents
  • Paints
  • Medicines
  • Alloys
  • Fertilisers
  • Foods
• Why are alloys used instead of pure metals?

  Alloys are harder than pure metals
• How is Rf calculated?

  Distance moved by the spot / solvent distance
• What does an Rf value of 0.85 indicate about a compound?

  It has a higher affinity for the solvent
• What are the tests for hydrogen, oxygen, carbon dioxide, and chlorine?

  • Hydrogen: pop with burning splint
  • Oxygen: glowing splint relights
  • Carbon dioxide: turns limewater milky
  • Chlorine: bleaches damp litmus paper
• What are the flame test results for different compounds?

  • Lithium: crimson red flame
  • Sodium: yellow flame
  • Potassium: lilac flame
  • Calcium: orange red flame
  • Copper: green flame
• How do you test for carbonate anions?

  Add dilute acid and observe fizzing
• How do you test for sulfate ions?

  Add Ba2+ solution and observe precipitate
• What do you observe when testing for chlorides with silver nitrate?

  White precipitate of silver chloride forms
• What is the result of testing bromides with silver nitrate?

  Cream precipitate of silver bromide forms
• What is the result of testing iodides with silver nitrate?

  Yellow precipitate of silver iodide forms
• What are instrumental methods?

  Accurate, sensitive, and rapid methods
• Describe flame emission spectroscopy.

  • Identifies metal ions in solution
  • Measures exact wavelength of emitted light
  • Allows for definite identification
  • Concentration found by light intensity
  • Intensity vs concentration graph used
• What are cations and anions?

  Cations are positive ions; anions are negative ions