Study Notes
Chromatography is a technique used to separate mixtures of soluble substances and identify them based on their movement through a medium. It involves placing a sample on a stationary phase and allowing a solvent to carry the components at different rates.
- Paper Chromatography — a method to separate mixtures using paper as the stationary phase. Example: Separating ink into its component dyes.
- Rf Value — the ratio of the distance traveled by a substance to the distance traveled by the solvent. Example: If a dye travels 2 cm and the solvent travels 5 cm, the Rf value is 0.4.
- Locating Agent — a chemical used to make colorless substances visible on a chromatogram. Example: Using ninhydrin to detect amino acids.
Exam Tips
Key Definitions to Remember
- Paper Chromatography: A method to separate mixtures using paper.
- Rf Value: Ratio of the distance traveled by a substance to the distance traveled by the solvent.
- Locating Agent: A chemical that makes invisible substances visible.
Common Confusions
- Confusing the solvent front with the distance traveled by substances.
- Using pen instead of pencil to draw the baseline.
Typical Exam Questions
- What is chromatography used for? To separate and identify components in a mixture.
- How do you calculate the Rf value? Divide the distance traveled by the substance by the distance traveled by the solvent.
- Why is a pencil used to draw the baseline? Because pencil does not dissolve in the solvent.
What Examiners Usually Test
- Understanding of how to set up and interpret a chromatogram.
- Ability to calculate and use Rf values to identify substances.