Problem 27 - A Complete Resource Book in Chemistry for JEE Main

Question

In paper chromatography, (a) mobile phase is liquid and stationary phase is solid (b) mobile phase is solid and stationary phase in solid (c) mobile phase is liquid and stationary phase is liquid (d) mobile phase is solid and stationary phase is liquid.

Step-by-Step Solution

Answer

(a) mobile phase is liquid and stationary phase is solid.

Step 1: Understand the Concept of Paper Chromatography

Paper chromatography is a laboratory technique used to separate mixtures into their individual components. In this method, the stationary phase is typically a solid, namely the paper, while the mobile phase is usually a liquid that moves through the stationary phase.

Step 2: Interpret the Options

Option (a) states that the mobile phase is liquid and the stationary phase is solid. Option (b) mentions both phases as solid. Option (c) suggests both phases are liquid. Option (d) describes the mobile phase as solid and the stationary phase as liquid.

Step 3: Match the Concept to the Options

Given that in paper chromatography, the mobile phase is indeed a liquid (solvent) that moves through the stationary phase, which is solid (paper), option (a) accurately describes this setup.

Key Concepts

Mobile Phase

In paper chromatography, the mobile phase is an essential component that facilitates separation. It is typically a liquid.
This liquid can be a mixture of solvents or a single pure solvent. The choice of solvent depends on the chemical properties of the substances being separated. The mobile phase flows through the stationary phase, carrying substances with it. Here are some key points about the mobile phase:

• The liquid nature of the mobile phase allows the sample to dissolve and move.
• The interaction between the mobile phase and the substances determines the speed and extent of movement.
• Solubility in the mobile phase influences how far each component travels.

As the mobile phase travels up the paper, it separates the mixture into individual components based on solubility and interaction.

Stationary Phase

In paper chromatography, the stationary phase is the medium through which the mobile phase travels. It is typically a solid, most often a strip or sheet of filter paper. This is referred to as the "stationary" because it does not move during the experiment.
It plays a crucial role in separating the substances based on their affinities. Here are some important aspects about the stationary phase:

• The stationary phase retains some components more than others, influencing their movement.
• The properties of the paper, such as porosity, contribute to the separation process.
• Stronger interactions with the stationary phase slow down the movement of components.

The combination of the stationary phase interacting with the mobile phase helps to achieve the separation of complex mixtures into pure parts.

Laboratory Technique

Paper chromatography is a simple yet effective laboratory technique used widely for separating mixtures. It is especially useful for identifying unknown components in a mixture, as well as for purifying compounds.
To perform paper chromatography:

• First, a spot of the mixture is placed on a piece of chromatography paper.
• The paper is then suspended in a container with the mobile phase.
• As the mobile phase travels up the paper, it takes the components of the mixture with it.

This technique is based on the partitioning behavior between the mobile phase and the stationary phase. A crucial feature of paper chromatography is its simplicity and low cost, making it accessible for educational purposes and small labs. Plus, it requires only small amounts of materials and can effectively separate and analyze complex mixtures.