12.3 Chromatography
Click on any question below to reveal the interactive flashcard answer key:
14. Describe how paper chromatography is used to separate mixtures.
It partitions components of a soluble sample mixture between a stationary phase (cellulose paper) and a mobile phase (suitable running solvent) based on their relative solubility and affinity.
15. How are unknown substances identified on a chromatogram?
By matching and comparing their vertical migration position and travel profiles directly side-by-side with known reference standard spots.
16. How can you determine if a substance is pure or impure using a chromatogram?
A completely pure substance resolves to yield a single isolated spot, whereas an impure substance resolves into multiple vertical spots representing different components.
17. How are mixtures of soluble colourless substances separated using chromatography?
By running the chromatogram in a suitable solvent, followed by applying or spraying a chemical locating agent (or using UV light irradiation) to make the invisible spots visible.
18. State the equation for calculating the Rf value.
Rf =
distance travelled by targeted substance
distance travelled by solvent front