Problem 6 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is correct for lyophilic sol? (a) irreversible sol (b) formed from inorganic substances (c) readily coagulated by addition of electrolyte (d) self stabilized

Step-by-Step Solution

Answer

The correct option is (d) self stabilized.

Step 1: Understanding Lyophilic Sols

Lyophilic sols are colloidal solutions where the dispersed particles have a strong affinity for the dispersion medium (usually water). This makes them stable and not easily coagulated.

Step 2: Characteristics of Lyophilic Sols

Lyophilic sols are considered to be reversible; they can be reformed by simply adding the dispersion medium without any specific treatment needed.

Step 3: Identifying the Correct Option

Given the options, the characteristic that best describes lyophilic sols is that they are often self-stabilized due to the strong interaction between the particles and the solvent.

Key Concepts

Colloidal Solutions

Colloidal solutions, or colloids, are mixtures where one substance is dispersed evenly throughout another. In such a system, the dispersed substance is finely divided, with particles typically ranging between 1 nanometer and 1000 nanometers in diameter.
These particles do not settle out over time and cannot be separated by ordinary filtration methods because they are too small to be captured by regular filters.
Colloids can appear cloudy or translucent, depending on the size and concentration of the dispersed particles.

• The dispersion medium acts as a continuous phase that surrounds the dispersed particles.
• Colloids exist in various forms such as sols, gels, and aerosols, based on the states of the dispersed phase and the dispersion medium.

Understanding the stability and properties of colloidal solutions is crucial in many industrial and research applications.

Dispersion Medium

In colloidal solutions, the dispersion medium is the substance in which colloidal particles are dispersed. It forms the continuous phase of the colloid.
The choice of dispersion medium strongly influences the stability and behavior of the colloid.

• Typically, the dispersion medium is a liquid, with water being the most common choice because of its capacity to dissolve many substances.
• However, gases and solids can also serve as dispersion mediums, depending on the type of colloidal system being formed.

The interaction between the colloidal particles and the dispersion medium is key to determining whether a colloid is lyophilic or lyophobic.
In lyophilic sols, the dispersed particles have a natural affinity for the dispersion medium, leading to enhanced stability.

Coagulation

Coagulation refers to the process where colloidal particles aggregate to form larger particles, ultimately leading to their precipitation out of the dispersion medium.
This process can lead to the breakdown of the colloidal system.
Here are some key points about coagulation:

• The addition of electrolytes can induce coagulation by neutralizing the surface charge on the colloidal particles, leading to their agglomeration.
• Environmental changes like altering the pH or temperature can also affect coagulation.
• Lyophilic sols are inherently resistant to coagulation due to strong interactions between the particles and the dispersion medium. This unique feature makes lyophilic sols stable against coagulation, unlike lyophobic sols.

Coagulation is an important consideration in the application and formulation of colloidal solutions across different industries.

Reversible Colloids

Reversible colloids are special types of colloidal solutions where the original system can be restored if the dispersion medium evaporates or if the colloid is disturbed in some way.
Lyophilic sols exhibit this reversible behavior due to their inherent properties.

• Adding the dispersion medium back to a reversibly coagulated lyophilic sol can return it to its original dispersed state without any intricate steps.
• This characteristic contrasts with irreversible colloids, where the colloid, once disturbed, cannot easily revert to its original state.
• The reversibility aids in industrial applications where control over the colloid's state is crucial in processing and product formulation.

The ability to be reversible underscores the utility of lyophilic sols in practical and commercial uses, such as in food products, pharmaceuticals, and cosmetic formulations.