The principle of column chromatography is based on th ability of the constituents to

Analysis

This question tests your understanding of Separation Techniques, specifically Chromatography, which is a core topic in the Chemistry syllabus for JAMB and WASSCE. You are asked to identify the fundamental principle that allows column chromatography to separate a mixture.

Concept Explanation

Column Chromatography is a technique used to separate components of a mixture based on the differences in their adsorption or partition between two phases:

1. The Stationary Phase: A solid material (usually silica gel or alumina) packed inside a glass column.
2. The Mobile Phase: A solvent (eluent) that flows through the column.

As the mixture travels through the column with the solvent, the different components interact with the stationary phase to varying degrees. Some components "stick" (adsorb) more strongly to the stationary phase, while others remain more soluble in the mobile phase. Because of these differences in affinity, the components travel through the column at different rates.

Step-by-Step Solution

1. Analyze the movement: As the solvent flows down the column, the components of the mixture are carried along.
2. Differential rates: Because each component has a different affinity for the stationary phase versus the mobile phase, they do not move at the same speed.
3. Separation: The component that has the least affinity for the stationary phase moves faster and exits the column first, while the component with the highest affinity moves the slowest.
4. Conclusion: The entire process relies on the fact that these constituents move at different speeds through the stationary phase, allowing them to be collected separately at different times.

• Option A & B: Chromatography is generally a physical separation technique; it does not rely on chemical reactions between the constituents or the solvent.
• Option C: Dissolving in each other is not the mechanism of separation; the components are already dissolved in the mobile phase.
• Option D: This accurately describes the physical basis of the separation.

Final Answer

The correct option is D.

Exam Tip

Think of chromatography like a race on a track with obstacles. The "runners" (constituents) have different levels of energy and agility (affinity). Those who are less hindered by the obstacles (stationary phase) finish the race (exit the column) faster than those who get stuck or slowed down by them. This difference in speed is exactly how you separate them!