Problem 3 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

A sample of red ink (a colloidal suspension) is prepared by mixing eosin dye, egg white, HCHO and water. The component which ensures stabilitiy of the ink sample is :(a) Egg white (b) Water (c) \(\mathrm{HCHO}\) (d) Eosin dye

Step-by-Step Solution

Answer

The egg white ensures the stability of the ink sample.

Step 1: Evaluate the Role of Each Component

Examine the roles each component plays in the colloidal suspension. Egg white is known to be a protein that can act as an emulsifying agent or stabilizer. Water is the medium. HCHO stands for formaldehyde, which acts as a preservative. Eosin dye provides color.

Step 2: Identify the Stabilizing Agent

Considering the nature of colloidal suspensions, they often require a stabilizer to prevent the particles from aggregating. In this context, the stabilizer is the component that facilitates the stability of the colloidal system.

Step 3: Determine the Answer Based on Component Roles

Knowing that egg white is a protein and proteins are often used as stabilizers in colloidal mixtures, conclude that the stability of the ink is ensured by the egg white due to its ability to prevent aggregation.

Key Concepts

Emulsifying Agents

Emulsifying agents are substances that help two immiscible liquids, like oil and water, to mix into a stable colloid. These agents work by lowering the surface tension between the different phases and forming a protective layer around dispersed particles. This action prevents the particles from coming together and causing the colloid to separate.
In the case of the red ink colloidal suspension presented in the problem, egg white acts as the emulsifying agent.
Egg white contains proteins which are excellent at forming films around particles, promoting uniform dispersion of the eosin dye within the water. The surface-active properties of protein enable them to interact with both water and dye, facilitating stable distribution and preventing aggregation over time.

Role of Proteins in Colloids

Proteins play a critical role in stabilizing colloidal systems. They are multi-functional macromolecules that can act as emulsifiers due to their amphiphilic nature.
This means they have both hydrophobic (water-repelling) and hydrophilic (water-attracting) parts, allowing them to interact with and stabilize different phases in a colloid.

• Their amphiphilic structure enables them to bind at interfaces between water and other molecules, like dyes or oils.
• They form a film around droplets or particles, which acts as a barrier to coalescence or aggregation, keeping the mixture stable.
• They're capable of altering the viscosity of solutions, affecting how particles move and are stabilized in the suspension.

In the exercise scenario, egg white, rich in proteins, serves as the stabilizer by forming a protective layer around the dye particles, ensuring the red ink remains consistently mixed.

Colloidal Suspension Components

In any colloidal suspension, different components serve distinct purposes to maintain stability and function. Understanding these roles can help identify how each contributes to the system.
Let's break down the components in the red ink example:

• Egg White: Acts as the main stabilizer, thanks to its protein content.
• Water: Serves as the solvent or dispersing medium, providing the liquid base in which other components are distributed.
• Formaldehyde (HCHO): Functions as a preservative, ensuring the longevity of the colloid by preventing microbial growth.
• Eosin Dye: Provides the rich color characteristic of red ink, evenly dispersed throughout the water due to the stabilizing action of the egg white.

Each component plays a unique and essential role in creating a stable and functional colloidal suspension. Egg white stands out by ensuring the other constituents remain uniformly distributed, highlighting the intricacies of constructing effective colloidal systems.