Problem 139 - A Complete Resource Book in Chemistry for JEE Main

Question

A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as (a) Solid sol (b) Emulsion (c) Sol (d) Gel

Step-by-Step Solution

Answer

The colloidal system is classified as (c) Sol.

Step 1: Understand the components of the colloidal system

In the given exercise, we are considering a colloidal system where the dispersed phase is solid, and the dispersion medium is liquid. The job is to identify the classification of such a system.

Step 2: Review the options

Look at the options given: (a) Solid sol, (b) Emulsion, (c) Sol, and (d) Gel. Note that a "Solid sol" has a solid phase dispersed in another solid, an "Emulsion" consists of liquid dispersed in liquid, a "Sol" has a solid dispersed in a liquid, and "Gel" has a liquid dispersed in a solid.

Step 3: Match characteristics with given options

Since the system has a solid as the dispersed phase and a liquid as the dispersion medium, it matches with the definition of a "Sol" where solid particles are dispersed in a liquid medium.

Key Concepts

Dispersed Phase

In colloidal systems, **the dispersed phase** refers to the tiny particles that are distributed throughout another substance, known as the dispersion medium. These particles are microscopic, ranging approximately from 1 nanometer to 1 micrometer in size. This minuscule size allows them to remain suspended and evenly distributed rather than settling out.

• They can be in different states such as solid, liquid, or gas.
• The state of the dispersed phase directly influences the classification of the colloidal system.
• In a sol, for instance, the dispersed phase is solid.

Understanding the nature of the dispersed phase is crucial in identifying the type of colloidal system. In this exercise, we're focusing on a colloidal system where the dispersed phase is solid, playing a key role in classifying the solution as a sol.

Dispersion Medium

The **dispersion medium** is the substance in which the dispersed phase is spread. It acts as the host or continuous phase. Much like the dispersed phase, the dispersion medium can also exist in solid, liquid, or gaseous states.

• A liquid dispersion medium, like water or alcohol, is common in sols and emulsions.
• The state of the dispersion medium helps determine the specific type of colloidal system, as different combinations produce different classifications.
• For instance, a liquid dispersion medium with a solid dispersed phase characterizes a sol.

In the context of the given exercise, the dispersion medium is a liquid. This means that it provides the environment in which solid particles are dispersed, confirming the nature of the colloid as a sol.

Sol

**Sol** is a type of colloidal system where solid particles are dispersed in a liquid medium. This gives sols a characteristic cloudy appearance due to the scattering of light, known as the Tyndall effect.

• Common examples include paints, inks, and blood.
• Sols can be stable or require stabilizers to prevent particles from settling out.
• They can be further categorized into lyophobic or lyophilic sols based on the interaction between the particles and the liquid medium.

In the exercise, recognizing the solid as the dispersed phase within a liquid medium led to classifying the system as a sol. Understanding concepts like sol is essential for identifying and working with colloidal systems, highlighting their versatile and widespread nature in both natural and industrial applications.