Problem 26 - A Complete Resource Book in Chemistry for JEE Main

Question

Solid aerosol in an example of colloidal system of (a) liquid dispersed in gas (b) liquid dispersed in gas (c) solid dispersed in gas (d) solid dispersed in liquid

Step-by-Step Solution

Answer

Solid aerosol is a colloidal system of solid dispersed in gas, option (c).

Step 1: Understanding the Definitions

First, we need to understand what a colloidal system is. A colloidal system, or colloid, consists of two phases: the dispersed phase and the dispersion medium. In the given problem, 'solid aerosol' is the term that requires classification based on the dispersed phase and the medium.

Step 2: Identifying the Dispersion Medium

The term 'aerosol' refers to colloidal systems where the dispersion medium is gas. Therefore, in a solid aerosol, the dispersion medium is gas.

Step 3: Identifying the Dispersed Phase

In a solid aerosol, the dispersed phase is a solid. Examples include smoke and dust, where solid particles are suspended in a gas (air).

Step 4: Matching with Options

Now, we compare our findings to the given options. Since solid aerosol involves solid dispersed in gas, we focus on the options: (a) liquid dispersed in gas (b) liquid dispersed in gas (c) solid dispersed in gas (d) solid dispersed in liquid. The correct match is option (c): solid dispersed in gas.

Key Concepts

Dispersed Phase

In a colloidal system, the dispersed phase is made up of tiny particles that are distributed, or dispersed, throughout another substance. These particles are not dissolved; instead, they are suspended. This suspension consists of very fine particles, generally ranging from 1 to 1000 nanometers in size.
In a solid aerosol, the dispersed phase is solid. For example, imagine smoke from a fire. The smoke particles are small bits of solid material that are dispersed in the surrounding air. Dust clouds formed in the atmosphere also serve as examples where solid particles are dispersed in the air. Seeing how these solid particles do not settle quickly, they create a stable colloidal system, maintaining suspension due to their small size.

Dispersion Medium

The dispersion medium is the continuous phase in which the dispersed particles are distributed evenly. Just as water can be the medium for dissolved salt, the medium in colloidal systems can vary between different types, such as liquid, solid, or gas.
In the case of aerosols, the dispersion medium is a gas. Consider the air in the atmosphere; it acts as the dispersion medium for many colloids, like smoke and mist. In the specific example of solid aerosols, the surrounding air, or gas, allows the solid particles to remain suspended, serving as a vehicle for the particles to disperse through. The nature of this medium prevents the dispersed phase particles from settling quickly, ensuring a stable system over time.

• Key point: Remember that the dispersion medium is what the dispersed phase is distributed in.
• In solid aerosols, the gas is the dispersion medium.

Solid Aerosol

A solid aerosol is a classic example of a colloidal system where solid particles are dispersed in a gaseous medium. This term often brings to mind phenomena like smoke from a fire or urban dust and pollution.
In these systems, the invisible gas framework (usually air) supports tiny solid particles. The interaction between the dispersed solids and the gas medium creates stability in the system, allowing these particles to remain as suspended "clouds" in the air.

• Characteristics: Solid aerosols are visible in the form of smoke, dust storms, or volcanic ash clouds.
• Behavior: They remain suspended in the air for long periods due to the size of the particulate matter coupled with the dispersal within the gas.

Understanding solid aerosols helps in studying environmental science, particularly air quality and pollution impacts, as these can carry various materials through the air over distances.