Chromatography

• What technique is used to identify substances in a mixture?

  Paper chromatography
• What are the four ways scientists use to separate mixtures?

  Filtration, crystallization, distillation, chromatography
• How does paper chromatography separate substances?

  Based on their different solubilities
• What is the first step in performing paper chromatography with colored pens?

  Draw a pencil line near the bottom
• What is the purpose of the solvent in paper chromatography?

  To dissolve substances and carry them up
• What do we call the paper used in chromatography?

  Chromatography paper
• What are the stationary and mobile phases in paper chromatography?

  Stationary phase is paper; mobile phase is solvent
• What does a single spot indicate in chromatography?

  The substance is a pure compound
• How does solubility affect the movement of substances in chromatography?

  More soluble substances travel further up
• Why do we draw the starting line in pencil?

  To prevent the line from moving with solvent
• How do you identify an unknown substance using paper chromatography?

  Measure distance moved and calculate RF value
• What is the formula to calculate the RF value?

  RF = distance moved by substance / distance moved by solvent
• What does it mean if multiple substances have the same RF value?

  They may need further analysis for identification
• What should you do if the substance has never been analyzed before?

  Conduct further analysis to identify it
• What are the steps involved in paper chromatography?

  1. Draw a pencil line on chromatography paper
  2. Place dots of colors on the line
  3. Immerse the paper in a solvent
  4. Allow the solvent to move up the paper
  5. Observe the separation of colors
  6. Measure distances and calculate RF values
• What are the key facts about pure compounds and mixtures in chromatography?

  • Pure compounds produce a single spot
  • Mixtures may separate into multiple spots
  • Solvent choice can affect spot positions