Question

The principle of column chromatography is :

• A. Capillary action.
• B. Gravitational force.
• C. Differential adsorption of the substances on the solid phase.
• D. Differential absorption of the substances on the solid phase.

Answer 1

The Correct Option is C

Column chromatography is a widely used method for purifying individual chemical compounds from mixtures of compounds. The principle of column chromatography lies in the differential adsorption of substances on the solid phase.

1. In column chromatography, the mixture to be separated is dissolved in a fluid called the mobile phase. This solution is passed through a column packed with a porous solid material known as the stationary phase.
2. The substances in the mixture interact with the stationary phase by adsorbing onto the surface of the solid particles. Different substances have different strengths of adsorption due to their varying affinities for the stationary phase material.
3. The key principle here is adsorption: As the mobile phase travels through the column, it carries along the different substances in the mixture at various rates because of their varying adsorption to the stationary phase.
4. Substances with stronger adsorption to the stationary phase move more slowly through the column, while those with weaker adsorption move faster. This differential rate of movement across the stationary phase results in the separation of the substances in the mixture.
5. After the separation is complete, individual compounds can be collected separately as they elute (or drip) out of the column at different times.

Given this explanation, option "Differential adsorption of the substances on the solid phase" accurately describes the principle of column chromatography.

Let's briefly rule out the other options:

• Capillary action: This is not relevant to the separation principle in column chromatography, as it refers to the movement of liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension.
• Gravitational force: While gravity assists in the movement of the mobile phase through the column, it is not the principle by which substances are separated.
• Differential absorption of the substances on the solid phase: Absorption involves the volume of the substances rather than the surface interactions (as in adsorption). In chromatography, the separation is due to the surface interaction of substances (adsorption) rather than volume interactions.

Therefore, the correct answer is "Differential adsorption of the substances on the solid phase."