Problem 48 - A Complete Resource Book in Chemistry for JEE Main

Question

The solution of rubber is an example of (a) lyophobic colloid (b) multimolecular colloid (c) associated colloid (d) macromolecular colloid

Step-by-Step Solution

Answer

Rubber is an example of a macromolecular colloid.

Step 1: Identify the Components

In colloidal systems, the components can be a dispersed phase and a dispersion medium. First, identify rubber's nature as a material.

Step 2: Understand Colloid Categories

Learn that lyophobic colloids have little attraction between particles and the medium, multimolecular colloids form from aggregates of small molecules, associated colloids form micelles at certain concentrations, and macromolecular colloids consist of large molecules dispersed in a medium.

Step 3: Examine Rubber

Rubber is made of large polymeric chains and is a high molecular weight compound. This fits the description of a macromolecular colloid because the large molecules form the dispersed phase.

Step 4: Compare with Colloid Types

Lyophobic, multimolecular, and associated colloids do not align with rubber's characteristics. Rubber's nature as a polymer fits with the macromolecular colloid category.

Key Concepts

Lyophobic Colloid

Lyophobic colloids, or "solvent-hating" colloids, are a type of colloidal system where there is very little affinity between the dispersed particles and the dispersion medium. This weak interaction can cause the colloid to be unstable, which means that it can easily separate out into its components if disturbed by changes in temperature, pressure, or the addition of other substances. These are typically not self-sustaining.

Here are some characteristics of lyophobic colloids:

• They require stabilizing agents to maintain their dispersion.
• They have little natural affinity for the medium, hence are harder to form.
• Metals like silver and gold, when finely divided, can form lyophobic colloids in water.

Because of the need for stabilizers, lyophobic colloids are important in various industrial applications, where their separation or coagulation properties can be leveraged.

Multimolecular Colloid

Multimolecular colloids are formed by the aggregation or grouping of a large number of atoms or molecules where each particle consists of an aggregate rather than a single large molecule. These aggregates then form the dispersed phase in a colloid.

Some key points about multimolecular colloids:

• Typically consist of small molecules or ions grouped together.
• Common examples include sulfur sols formed by mixing hydrogen sulfide and sulfur dioxide, where molecules of sulfur aggregate.
• They often depend on the nature of the intermolecular forces and stabilization agents to remain dispersed.

Unlike macromolecular colloids, multimolecular colloids include smaller, bonded structures. They can be stabilized by additional substances to prevent coagulation or precipitation.

Associated Colloid

Associated colloids are unique because they can act as true solutions at low concentrations and turn into colloidal solutions at higher concentrations. This transition is thanks to the formation of micelles when a certain concentration is exceeded, known as the critical micelle concentration (CMC).

Important aspects of associated colloids include:

• These are often made of soap or detergent molecules that align in such a way to shield their hydrophobic parts from the dispersion medium.
• Upon reaching the CMC, the molecules rearrange to form micelles, which trap hydrophobic tails at the center.
• They are useful in cleaning and detergent actions where they help remove dirt and grease.

An understanding of associated colloids is essential in industries like cleaning supplies and pharmaceuticals, which utilize their ability to manage both hydrophilic and hydrophobic interactions.