Which separation technique is used to separate coloured substances dissolved in a solvent?

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

Answer: (C)

Chromatography works because different substances interact differently with the stationary phase (like paper) and dissolve to different extents in the moving solvent. When a mixture of coloured substances is placed on the stationary phase and the solvent (mobile phase) moves through it, each component travels at its own rate. Substances that dissolve well in the solvent and interact less with the paper move farther, while those that stick more to the paper stay behind. This separation creates distinct coloured spots or bands, allowing each component to be seen individually.

That’s why it’s the method used for separating coloured substances dissolved in a solvent—filtration can’t separate dissolved components, distillation and evaporation rely on boiling points to remove solvent, while chromatography specifically exploits differences in solubility and adhesion to achieve separation.