Problem 35 - A Complete Resource Book in Chemistry for JEE Main

Question

The diameter of colloidal particle ranges from (a) \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\) (b) \(10^{-6} \mathrm{~m}\) to \(10^{-3} \mathrm{~m}\) (c) \(10^{-12} \mathrm{~m}\) to \(10^{-9} \mathrm{~m}\) (d) \(10^{-3} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\)

Step-by-Step Solution

Answer

The diameter of a colloidal particle ranges from (a) \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\).

Step 1: Understand Colloidal Particle Range

Colloidal particles are very small, typically larger than molecules but smaller than what the naked eye can see. Their size generally ranges from \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\). This range is defined by their ability to stay suspended and not settle out under the influence of gravity.

Step 2: Analyze the Given Options

Review the provided options for the range of colloidal particle diameters:- Option (a): \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\)- Option (b): \(10^{-6} \mathrm{~m}\) to \(10^{-3} \mathrm{~m}\)- Option (c): \(10^{-12} \mathrm{~m}\) to \(10^{-9} \mathrm{~m}\)- Option (d): \(10^{-3} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\)

Step 3: Match the Defined Range with Options

Compare each option to the standard colloidal size range. Option (a), at \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\), matches precisely with the typical size range of colloidal particles.

Step 4: Validate the Correct Option

Confirm that no other option matches the colloidal range specified in step 1. Options (b), (c), and (d) provide ranges that are outside the typical colloidal size range, either by being too large or too small.

Key Concepts

Particle Size Range

Colloidal particles have a very specific size range. They are larger than individual molecules but small enough that they can't be seen with the naked eye. The typical size range for these particles is from \(10^{-9} \mathrm{~m}\) to \(10^{-6} \mathrm{~m}\). This size allows them to remain suspended in a medium, not easily settling out due to gravitational pull.
This precise range distinguishes colloidal particles from either true solutions or suspensions, which have distinctly different size ranges. Recognizing the size of colloidal particles is crucial as it influences their behavior and interaction properties. For students, understanding this range is key to identifying colloidal systems in various scientific applications.

Colloidal Stability

Colloidal stability refers to the ability of colloidal particles to remain evenly distributed throughout the medium without settling or clumping together over time. This stability is essential because it affects the shelf life and effectiveness of colloidal systems like medicines, foods, and paints.
Factors influencing colloidal stability include:

• Electrostatic Repulsion: Like charges on the particle surfaces repel each other, preventing agglomeration.
• Steric Stabilization: Polymer layers or surfactants on the particle surface provide a physical barrier to prevent particles from coming too close.
• pH and Ionic Strength: Changes in pH and ionic strength can affect the charge on particle surfaces, altering stability.

Understanding these factors is critical for industries that rely on stable colloidal systems. For students, grasping these concepts helps in recognizing how collodials maintain their dispersed state.

Colloid Definition

A colloid is a type of mixture where one substance is dispersed evenly throughout another. Unlike a solution, where solutes dissolve completely, colloidal particles remain suspended because they are large enough to scatter light but too small to settle by gravity. This gives colloids their unique properties, like the Tyndall effect, where dispersed particles scatter light, making a beam visible in the colloid.
Colloids can be found in various forms depending on the state of the dispersed substance and the medium. Common types include:

• Sol: Solid particles in a liquid. Example: Paint.
• Emulsion: Liquid droplets in another liquid. Example: Milk.
• Aerosol: Solid or liquid particles in a gas. Example: Mist.

Understanding what makes a colloid helps in recognizing them in everyday life and in evaluating their applications in different scientific and industrial processes. For students, this clarifies the distinction between colloids and other mixtures, enhancing their comprehension of this important chemistry topic.