Paper chromatography

• What is chromatography used for?

  To separate substances in a mixture
• What are the two phases in chromatography?

  Mobile phase and stationary phase
• What is the mobile phase in chromatography?

  A liquid or a gas
• What is the stationary phase in chromatography?

  A solid or a thick liquid
• What happens during a chromatography experiment?

  • Substances move between mobile and stationary phases
  • An equilibrium is formed between the two phases
• How does the mobile phase interact with the stationary phase?


  The mobile phase moves through the stationary phase
• What determines how quickly a chemical moves in chromatography?

  Its distribution between the two phases
• What happens to chemicals that spend more time in the mobile phase?

  They move further through the stationary phase
• What is required for components in a mixture to separate in chromatography?

  • Components must spend different amounts of time in the mobile phase
• What do the separated components in chromatography form?

  Spots
• How does the solvent affect the number of spots formed?

  The number of spots may change with different solvents
• What does a pure substance form in chromatography?

  One spot in any solvent
• What is the stationary phase in paper chromatography?

  Chromatography paper
• What is the mobile phase in paper chromatography?

  The solvent (e.g., ethanol or water)
• What factors affect the time molecules spend in each phase during paper chromatography?

  • Solubility in the solvent
  • Attraction to the paper
• How do molecules with higher solubility behave in paper chromatography?

  They move further up the paper
• What is a chromatogram?

  • The result of chromatography analysis
• What is the Rf value in chromatography?

  The ratio of distances travelled by solute and solvent
• How do you calculate the Rf value?

  $Rf =$$\frac{B}{A}$
• What does a larger Rf value indicate?

  The substance moves further through the stationary phase
• How is chromatography used to identify substances in a mixture?

  • Run a pure sample alongside the mixture
  • Compare Rf values
  • Match indicates presence of substance
• How does the solvent affect the Rf value?

  Changing the solvent changes the Rf value
• What should you do to confirm the presence of a substance in a mixture?

  Test in multiple solvents
• What does it mean if Rf values match in all solvents?

  The reference compound is likely present
• What does it mean if Rf values match in some solvents only?

  The reference compound isn't present in the mixture
• What is the formula for Rf value?

  • $Rf =$$\frac{\text{distance travelled by substance}}{\text{distance travelled by solvent}}$
• What is the baseline in chromatography?

  • The starting point for the sample application
• What is the solvent front in chromatography?

  • The furthest point reached by the solvent
• What is the origin in chromatography?

  • The baseline where the sample is applied