11.5 Chromatography

• What does the term chromatography literally mean?

  Color writing
• What is chromatography used for?

  It is a separation technique used to separate materials in a mixture
• How does chromatography work in both school and professional labs?

  It works the same in both settings
• What are the two phases in chromatography?

  Mobile phase and stationary phase
• What determines how components in a mixture separate during chromatography?

  How much they prefer the stationary phase or the mobile phase
• What is the stationary phase used in this chromatography experiment?

  Paper
• Why is it important to use pencil for the baseline in chromatography?

  Because pen ink might leak into the mobile phase and spoil the separation
• How far from the base of the chromatography paper should the baseline be drawn?

  About 2 centimeters
• How should the food coloring dots be placed on the baseline?

  They should be placed about 1 centimeter apart
• What colors of food coloring are used in this experiment?

  Blue, yellow, red, and green
• What does it mean for a material to be a pure color in this context?

  It means it only has one color dissolved in it
• What is the purpose of using a capillary tube in this experiment?

  To suck up a small amount of liquid for application
• Why is it important to allow the color to dry between applications?

  To ensure a strong color without merging with adjacent dots
• What should be done to avoid cross-contamination of colors?

  Use a different capillary tube for each color
• What is the mobile phase used in this chromatography experiment?

  Water
• How is the mobile phase introduced in the chromatography setup?

  By putting water at the bottom of the paper
• What happens to the colors in the food dye during chromatography?

  They either dissolve into the water and move with it or stay on the paper
• How should the chromatography paper be positioned in the beaker?

  It should be suspended at the top of the beaker
• What is the purpose of marking a pencil line near the top of the chromatography paper?

  To indicate the distance the solvent has traveled
• How long should the chromatography be left in the solvent?

  About 15 minutes
• What does the RF value represent in chromatography?

  It measures how far the individual colors have traveled
• How is the RF value calculated?

  By dividing the distance the color has traveled by the distance the solvent has traveled
• What is the RF value for the yellow color if it traveled 20 mm and the solvent traveled 101 mm?

  $RF =$$\frac{20}{101} \approx 0.198$
• What RF values were calculated for the purple and blue colors?

  Purple is 63 and blue is 85
• What are the steps involved in setting up chromatography for food coloring?

  1. Draw a baseline on chromatography paper using pencil.
  2. Mark points for food coloring application.
  3. Apply food coloring using a capillary tube.
  4. Allow colors to dry between applications.
  5. Prepare the mobile phase (water) and ensure it does not exceed the dots.
  6. Suspend the paper in the beaker with water.
  7. Wait for the solvent to rise and separate the colors.
• What observations can be made after chromatography is complete?

  • The unknown food coloring contains yellow and blue.
  • The red food coloring is not present in the unknown.
  • The red food coloring is not pure, showing purple and orange marks.