Which technique separates substances based on movement through a medium and interactions with stationary and mobile phases?

Which technique separates substances based on movement through a medium and interactions with stationary and mobile phases?

• A. Filtration
• B. Chromatography
• C. Distillation
• D. Evaporation

Answer: (B)

Chromatography separates substances by letting a solvent move through a medium while the components interact differently with the solid phase versus the liquid phase. As the mobile phase (the solvent) travels, each component has a specific affinity for the stationary phase (the solid on the medium, like paper or a thin layer). Components that stick more to the stationary phase move more slowly, while those that prefer the solvent travel faster. This varying pace causes the mixture to split into separate spots along the medium, giving distinct bands that reflect each component. For example, on paper a dye that is highly polar may cling to the paper and lag behind, while a less polar dye dissolves in the solvent and moves farther. The distance each component travels relative to the solvent front can be quantified with an Rf value, but the essential idea is the differential movement due to partitioning between stationary and mobile phases. Filtration, distillation, and evaporation separate mainly by particle size, boiling point, or phase changes, not by movement through a medium with differing affinities to a stationary phase.

Chromatography separates substances by letting a solvent move through a medium while the components interact differently with the solid phase versus the liquid phase. As the mobile phase (the solvent) travels, each component has a specific affinity for the stationary phase (the solid on the medium, like paper or a thin layer). Components that stick more to the stationary phase move more slowly, while those that prefer the solvent travel faster. This varying pace causes the mixture to split into separate spots along the medium, giving distinct bands that reflect each component.

For example, on paper a dye that is highly polar may cling to the paper and lag behind, while a less polar dye dissolves in the solvent and moves farther. The distance each component travels relative to the solvent front can be quantified with an Rf value, but the essential idea is the differential movement due to partitioning between stationary and mobile phases.

Filtration, distillation, and evaporation separate mainly by particle size, boiling point, or phase changes, not by movement through a medium with differing affinities to a stationary phase.