C8 Chemical Analysis

• Pure substance


  A single element or compound, not mixed with any other substance
• Formulation


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


  1. Draw start line

  2. Place sample on line

  3. Fill beaker with solvent

  4. Hang paper in beaker

  5. Solvent travels up paper

  6. Mark finish line

  7. Dry paper
• Rf value


  Distance moved by the spot / distance moved by solvent
• Rf value of 0.85

  Compound has higher affinity for the solvent than for the paper
• Tests for gases


  • Hydrogen - pop with burning splint
  • Oxygen - glowing splint relights
  • Carbon dioxide - turns limewater milky
  • Chlorine - bleaches damp litmus paper
• 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
• Sodium hydroxide tests


  1. Cu2+ forms blue precipitate

  2. Fe2+ forms dirty green precipitate

  3. Fe3+ forms brown precipitate

  4. Al3+, Ca2+, Mg2+ form white precipitates, Al(OH)3 dissolves in excess
• Carbonate test


  Add dilute acid, fizzing observed as CO2 is released
• Sulfate test


  Add BaCl2 solution, white precipitate of BaSO4 forms
• Halide tests


  Add AgNO3 (acidified)

  Chlorides - white precipitate AgCl

  Bromides - cream precipitate AgBr

  Iodides - yellow precipitate AgI
• Instrumental methods


  Accurate, sensitive and rapid methods useful when sample amount is very small
• Flame emission spectroscopy


  Spectroscope measures exact wavelength of light emitted by metal ion

  Intensity of light emitted measures concentration of metal ion
• Cations


  Positive ions
• Anions


  Negative ions