Chemical Analysis

• what are the boiling and melting points like for pure substances

  specific, pure substances melt and boil at a fixed temperature, so can be used to distinguish between pure and mixtures
• what is a formulation

  a mixture that has been designed as a useful product
• how are formulations made

  by mixing components in carefully measured quantities to get the required properties
• examples of formulations

  • fuels
  • cleaning agents
  • paints
  • medicines
  • alloys
  • fertilisers
• a method used to separate dyes

  chromatography
• what two phases are involved in chromatography

  stationary and mobile phase
• what does separation depend upon in chromatography

  on distribution of substances between the phases
• what is Rf value

  the ratio of the distance moved by a compound to the distance moved by the solvent
• how can you express Rf

  Rf = Distance moved by substance / Distance moved by solvent
• what value is Rf always below

  1
• what are values of Rf like in different solvents

  differ, can be used to identify a substance
• how many spots would you get for a pure substance

  one
• how many spots would you get in a mixture

  depends on number of substances present
• does solvent type alter number of spots found

  always the same for a pure substance, can differ for a mixture
• what is the test for hydrogen

  burning splint at the open end of a test tube of the gas, burns rapidly with a pop sound
• what is the test for oxygen

  use a glowing splint inserted into a test tube, the splint relights
• what is the test for carbon dioxide

  bubble through limewater (calcium hydroxide solution), the limewater turns milky (cloudy)
• what is the test for chlorine

  use litmus paper, when damp is bleached and turns white
• In chemistry what is a pure substance


  a substance made up of a single element or compound, not mixed with any other substances
• Which one is the substance with a relatively fast rate of travel?

  A

  
• Which one is the substance with the a relatively slow rate of travel?

  B

  
• Which one is the Insoluble part of the ink?

  C

  
• What is the name of the resulting paper we end up with?

  A Chromatogram

  
• Which is the mobile phase in paper chromatography?

  The solvent
• Which is the stationary phase in paper chromatography?

  The paper
• True or false?

  If you change either the mobile or stationary phase, you'll get a different Rf value.?

  True