chromatography

• How many known food colorings are used in the experiment?

  Four
• What is the first step in carrying out paper chromatography?

  Draw a horizontal pencil line
• How far from the bottom should the pencil line be drawn on the chromatography paper?

  About 2 cm
• Why do we need to leave at least 1 cm clear at each side of the pencil spots?

  To prevent colors from spreading into each other
• What is a capillary tube used for in this experiment?

  To put small spots of color
• What is the role of water in this chromatography experiment?

  It acts as the solvent
• How deep should the water be in the beaker?

  1 cm
• Why must the pencil line be above the water surface?

  To prevent washing off the ink
• What happens if the sides of the paper touch the beaker walls?

  It interferes with water movement
• Why do we usually put a lid on the beaker?

  To reduce evaporation of the solvent
• When should we remove the chromatography paper from the beaker?

  When water has traveled 3/4 up
• What do we mark on the paper after removing it from the beaker?

  The point where the water reached
• What does it indicate if the unknown color separates into three spots?

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

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

  Divide distance moved by chemical by solvent
• What should you do if multiple chemicals have the same RF value?

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

  Further analysis is needed to identify it