chromatography

• what is paper chromotography?

  allows you to separate substances based on their different solubilities
• why are different dyes in a substance separated in chromatography?

  as the solvent moves through the paper,

  different dyes which have different solubilities in the solvent

  are carried different distances

  due to different attractions to the paper
• T/F? Less soluble substances are carried further distances.

  False - more soluble substances travel further due to lower attraction to the paper
• why must the starting line be drawn in pencil

  pencil is insoluble in water - would not be carried up the paper and distrupt results
• how to calculate Rf value

  distance travelled by the substance / distance travelled by the solvent
• • Different substances may have the same Rf value. May need to repeat chromatography with other solvents to narrow down results
  • If a substance hasnt been analysed before, there won’t be an Rf value in the database
• what is the mobile phase in chromatography?

  the solvent which carries the substance through the stationary phase (the paper)