Question

Method by which lyophobic sol can be protected. (a) By addition of an electrolyte (b) By addition of oppositely charged sol. (c) By addition of lyophilic sol. (d) By bhoiling

Short answer

Lyophobic sols are protected by adding a lyophilic sol (Option c).

Step-by-step solution

Understanding Lyophobic Sols

Lyophobic sols are colloidal solutions where the dispersed phase has little to no affinity for the dispersion medium. As a result, they are unstable and can be easily precipitated by electrolytes.

Role of Stabilizing Agents

To protect a lyophobic sol from coagulation, stabilizing agents are added. These agents prevent the particles from clumping together and precipitating out.

Analyzing the Options

Let's evaluate each option: (a) Addition of an electrolyte could actually destabilize the sol, not protect it. (b) Addition of an oppositely charged sol can lead to coagulation because the opposites attract. (c) Addition of a lyophilic sol can protect by forming a protective layer around lyophobic particles, preventing them from clumping. (d) Boiling could destabilize the sol by increasing particle movement and collision.

Conclusion

The option that effectively prevents coagulation in lyophobic sols is (c) By addition of a lyophilic sol. Lyophilic sols increase stability by forming a protective sheath around lyophobic particles.

Key concepts

Colloidal Stability

Colloidal stability refers to the ability of a colloidal system to remain uniformly dispersed without particles clumping together and settling out. In colloids, especially lyophobic sols, this stability is crucial as it prevents the particles from aggregating and thus maintains the solution's even distribution. Lyophobic sols are inherently unstable due to the weak affinity between the dispersed particles and the dispersion medium.

For a colloid to be stable, several factors can come into play:

• Electrostatic Stabilization: The presence of charged particles creates an electrostatic repulsion, preventing the particles from coming too close and clumping.
• Steric Stabilization: Large molecules or polymers can create a physical barrier around particles, thereby preventing them from coming in contact with each other.
• Hydration: Water molecules surrounding the particles can create a shell of hydration that keeps the particles dispersed.

Enhancing colloidal stability is essential for various applications, including cosmetics, medicine, and food production, where a uniform texture and distribution are critical.

Protective Colloids

Protective colloids are substances added to a lyophobic sol to enhance its stability and prevent coagulation. These agents function by enveloping the particles of the lyophobic sol in a layer, thus reducing their tendency to aggregate.

These colloids work through the mechanism of steric stabilization, effectively forming a protective barrier around the dispersed particles. This barrier minimizes the interactions that can cause particles to clump together. Consider the following attributes:

• Chemical Affinity: Protective colloids demonstrate a strong chemical affinity towards the dispersion medium, ensuring the stability of the otherwise unstable lyophobic sol.
• Interfacial Activity: They reduce surface tension between the dispersed phase and dispersion medium, contributing to overall colloidal stability.
• Example Substances: Common protective colloids include gelatin, gum arabic, and starch, known for their ability to interact with lyophobic particles.

This addition is vital in processes where the stability and longevity of the colloid are paramount.

Coagulation Prevention

Preventing coagulation is crucial for maintaining the functionality and integrity of lyophobic sols. Coagulation occurs when the dispersed particles cluster together, leading to the formation of larger aggregates that eventually settle out of the dispersion medium.

Several strategies can be employed to prevent coagulation:

• Use of Lyophilic Sols: Adding a lyophilic sol serves as an effective protective measure. These sol particles interact favorably with the dispersion medium, lending stability to the lyophobic sol by creating a coating that prevents aggregation.
• Controlling Electrolyte Concentration: Avoiding or carefully controlling the addition of electrolytes is important since excess electrolytes can promote coagulation by neutralizing surface charges.
• Avoiding High Temperatures: High temperatures increase kinetic energy and collisions between particles, which can lead to coagulation. Thus, maintaining moderate temperatures can help in maintaining stability.

Understanding and implementing these methods effectively allows for the use of lyophobic sols across various industrial and scientific applications, ensuring their effectiveness and reliable storage over time.