chromatography

    Cards (9)

    • rpa
      1. draw a line near the bottom of a shet of filter paper
      2. add a spot of the ink to the line + place the sheet in a beaker of solvent
      3. the solvent used depends on what's being tested ( some compounds dissolve well in water)
      4. make sure the ink isnt touching the solvent
      5. place a lid on top of the container to stop the solvent evaporating
      6. each different dye in the ink will move up the paper at a different rate
      7. any insoluble dyes in ink = stay on baseline
      8. when solvent has reached the top of the paper = take paper out + leave it to dry
    • mobile phase : where the molecule can move ( liquid or gas)
    • stationary phase : where the molecules cannot move (solid or thick liquid)
    • molecules with a higher solubility in the solvent + less attracted to the paper will spend more time in the mobile phase and will be carried up the paper
    • rf value : substance/ solvent
    • chromatography method
      1. draw pencil line on chromatography paper
      2. place spot of food colouring on start line
      3. use a suitable solvent
      4. place solvent in beaker
      5. place paper in beaker
      6. so paper is in solvent
      7. solvent is below start line
      8. use a lid to stop solvent evaporating
      9. wait for solvent to travel up the chromatography paper untol top
      10. mark solvent front
      11. dry the chromatography paper
    • chromatogrpahy paper measurements:
      • measure distance between start line + centre of spot
      • measure distance between start line + solvent front
      • use of measurements to determine rf value
    • how different dyes are seperated by paper chromatogrpahy
      • solvent moves through paper
      • different dyes have different solubilities in solvent
      • different attractions for the apper
      • carried different distances
    • mistakes
      • if start line is in ink = ink would move on the paper
      • if water level is above start line = colours dissolve into water