Chromatography

• Chromatograghpy

  The process of separating the components of a mixture.
• What are the two phases involved in chromatography?

  The two phases are the stationary phase and the mobile phase.
• Why are components separated in chromatography?

  Components are separated based on their different solubility for the stationary and mobile phases.
• If compound A moves faster than compound B in chromatography, what can we conclude about their solubility?

  Compound A has a stronger solubility for the mobile phase than compound B.
• The base line


  What label is missing?

  
• What is the base line draw in?

  Pencil
• Why is the base line drawn in pencil?

  The base line is drawn in pencil because it is insoluble.
• How would you calculate RF?

  Distance travelled by spot divided by distance travelled by solvent.
• How would you calculate distance travelled by spot?

  By measuring the distance from the base line to the new spot position.
• How would you calculate the distance travelled by solvent?

  By measuring the distance from the base line to the solvent front.
• What is the solvent front?

  The solvent front is the point the solvent has reached as it moves up the paper.
• What is chromatography used for?

  It is a separation technique used to separate mixtures of soluble substances.
• What types of substances are commonly separated using chromatography?

  Colored substances such as food colorings, inks, dyes, or plant pigments.
• What does a chromatogram show?

  It shows the results after chromatography has occurred.
• What does one spot on a chromatogram indicate?

  It indicates that the substance is pure.
• How does chromatography separate pigments?

  Some pigments are more soluble than others, affecting how far they travel up the paper.
• What is the first step in performing chromatography with food colorings?

  Draw a straight line about 1 cm from the bottom of the chromatography paper.
• What happens when the chromatography paper is placed in water?

  The paper absorbs the water, and the pigments dissolve and move up the paper.
• What is the significance of the height of spots on a chromatogram?

  The higher the spot, the more soluble the substance is in the solvent.
• Why is it important to use a pencil instead of a pen for the start line in chromatography?

  Because pen ink would move up the paper with the pigments, contaminating the results.
• What does it mean if a pigment does not rise up the chromatography paper?

  It is insoluble in the solvent being used.
• What are the steps to perform standard chromatography?

  1. Draw a horizontal line about 1 cm from the bottom of chromatography paper.
  2. Place a small spot of the colored mixture on the line and allow it to dry.
  3. Lower the paper into a beaker with a suitable solvent without covering the pencil line.
  4. Observe the solvent rising and separating the pigments.
• What conclusions can be drawn from a chromatogram?

  • The number of spots indicates the number of substances in the mixture.
  • The height of the spots indicates the solubility of the pigments.
  • Matching spots with standard reference pigments can identify the pigments present.
• What is the difference between standard chromatography and radial chromatography?

  • Standard chromatography: pigments move upwards on the paper.
  • Radial chromatography: pigments move outwards from a central spot on filter paper.
• What is the role of solubility in chromatography?

  • Higher solubility means pigments travel further up the paper.
  • Lower solubility means pigments remain closer to the base line.
• RF = Distance travelled by spot / Distance travelled by solvent
• Chromatography is the separation technique that uses a stationary phase (paper) and a mobile phase (solvent)
• Rf values range from 0 to 1
• Paper chromatography separates different coloured dyes based on their relative solubilities in a solvent
• A higher Rf value shows greater solubility, meaning it has moved further along the paper than less soluble components