Chromatography

• 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 is the sample of food coloring referred to in the experiment?

  U for unknown
• 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
• What should be the distance between the pencil spots on the chromatography paper?

  Equal spaces with 1 cm clear at each side
• What is the purpose of the capillary tube in the experiment?

  To apply small spots of color
• What is the solvent used in this chromatography experiment?

  Water
• 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 during chromatography?

  To reduce evaporation of the solvent
• When should the chromatography paper be removed from the beaker?

  When the water has traveled 3/4 up
• What should be marked 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?

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

  $0.2$
• Why do RF values not have units?

  They are ratios of distances
• What should be done 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
• Where can students find questions on this required practical?

  In the vision workbook
• What is the method for carrying out paper chromatography?

  Apply spots, dip in solvent, analyze
• Why is it important to keep spots small in chromatography?

  To prevent colors from spreading together
• What is the role of the capillary tube in the chromatography process?

  To apply small spots of color
• What is the significance of the pencil line in chromatography?

  It serves as a starting point for colors
• How does evaporation affect the chromatography process?

  It can alter the solvent concentration
• What should be done if RF values are inconclusive?

  Conduct further analysis to identify chemicals