Problem 49 - A Complete Resource Book in Chemistry for JEE Main

Question

Smoke is a colloidal dispersion of a (a) solid in a gas (b) liquid in a gas (c) gas in a solid (d) gas in a gas

Step-by-Step Solution

Answer

Smoke is a colloidal dispersion of a solid in a gas (option (a)).

Step 1: Define Terminology

First, understand what a colloidal dispersion is. A colloidal dispersion consists of small particles of one substance (the dispersed phase) distributed throughout another substance (the continuous phase). These particles are larger than molecules but too small to be seen with the naked eye.

Step 2: Identify Components in Smoke

Smoke primarily consists of tiny solid particles suspended in a gas. These solid particles can include carbon, tar, and other combustion by-products from burning materials.

Step 3: Match to Given Options

Compare your identification of smoke's composition to the given multiple-choice options. Smoke corresponds to a solid dispersed in a gas.

Step 4: Verification

Double-check your identification: smoke is indeed a solid (combustion by-products) in a gas (air). This confirms that the correct answer aligns with the option ‘a’.

Key Concepts

Colloidal Dispersion

A colloidal dispersion is a type of mixture where tiny particles of one substance are evenly distributed throughout another substance. These particles, known as the dispersed phase, are not dissolved, but float around in the surrounding medium called the continuous phase.

Colloidal dispersions are distinct from solutions because the particles are larger than individual molecules, often in the range of 1 nanometer to 1 micrometer.

• Examples of colloidal dispersions include milk, which is a liquid dispersed in another liquid, or paint, a solid dispersed in a liquid.
• The particles in a colloid are small enough that they do not settle out quickly, remaining suspended.
• Due to the unique size of the dispersed particles, colloidal systems can scatter light, a property known as the Tyndall effect.

Understanding colloidal dispersions helps to explain various natural and industrial processes where different phases need to be uniformly distributed for functionality, such as in smoke, food products, and pharmaceuticals.

Solid in Gas

A solid in gas colloidal dispersion is a type of mixture where solid particles are dispersed in a gaseous medium. Smoke is a classic example of this phenomenon. When a material burns, not all of it combusts completely. The resulting tiny solid particles, often composed of carbon and other by-products, become dispersed in the air.

This dispersion creates smoke, which, while visible, consists of particles so small they remain suspended in the gas instead of settling immediately. Such dispersions are common in nature and human activities.

• Another everyday example of a solid in gas colloidal system is air pollution from industrial activities, where tiny solid pollutants are spread throughout the air.
• Solid in gas dispersions are significant in understanding how pollutants travel and disperse in the atmosphere.
• Managing solid in gas colloidal dispersions is crucial in environmental science to control air quality and protect health.

By studying these systems, scientists can create more efficient air filtration and pollution control technologies.

Dispersed Phase

The dispersed phase is a core component of any colloidal system. It refers to the fine particles or droplets that are spread out within another substance, known as the continuous phase. In the context of smoke, the dispersed phase consists of microscopic solid particles that result from incomplete combustion of materials.

The characteristics of the dispersed phase, such as size and charge, heavily influence the properties and stability of the colloidal system.

• The size of the particles in the dispersed phase determines whether the mixture will remain stable or if the particles will eventually settle.
• In a stable dispersion, the particles are small and evenly spread, with interactions preventing them from clumping together or settling.
• The charge of the particles can also play a role in stability, as like-charged particles repel each other, helping maintain dispersion.

Understanding the nature of the dispersed phase is essential for manipulating and using colloidal dispersions effectively in various applications, from food production to pharmaceuticals.