P2 chromotography

• What is the purpose of paper chromatography?

  To identify substances
• Why is it essential to learn the details of paper chromatography?

  It is a required practical
• What should you do before continuing with the chromatography video?

  Watch the previous video on atomic structure
• What is the method for carrying out paper chromatography?

  1. Draw a horizontal pencil line on chromatography paper.
  2. Mark five pencil spots for samples.
  3. Use a capillary tube to apply samples.
  4. Pour water into a beaker as solvent.
  5. Attach paper to a glass rod and lower it into the beaker.
  6. Ensure the pencil line is above water.
  7. Avoid touching the sides of the beaker.
  8. Cover the beaker to reduce evaporation.
  9. Remove paper when water reaches 3/4 up.
  10. Mark the water level and hang to dry.
• What do we label the unknown food coloring in chromatography?

  U for unknown
• Why should the spots of food coloring be kept small?

  To prevent colors from spreading into each other
• What is the depth of water used in the beaker for chromatography?

  1 cm
• What happens if the pencil line touches the water?

  The ink will wash off the line
• Why do we put a lid on the beaker during chromatography?

  To reduce evaporation of the solvent
• What does it indicate if the unknown color separates into three spots?

  It is a mixture of three colors
• How do we identify the chemicals in the food colors?

  By calculating the RF values
• How do you calculate the RF value for a chemical?

  Divide distance moved by chemical by solvent
• What is the RF value for color A if the distance is 14 mm and the solvent is 70 mm?

  0.2
• What does an RF value indicate?

  The identity of the chemical
• What should you do if multiple chemicals have the same RF value?

  Repeat the experiment with a different solvent
• What if a chemical has never been analyzed before?

  Further analysis is needed to identify it
• What resources can help with questions on paper chromatography?

  • Vision workbook
  • Online resources
  • Previous videos on chromatography