Question

Which method is used to destroy a sol? (a) Condensation (b) Dialysis (c) Diffusion (d) Addition of electrolyte

Short answer

The method used to destroy a sol is (d) Addition of electrolyte.

Step-by-step solution

Understanding the Methods

Consider each method and understand whether it can destabilize a sol or not. Condensation is a phase change from gas to liquid, does not particularly impact colloidal stability. Dialysis is a separation method used to remove small, dissolved ions from colloids, but it does not necessarily destabilize the sol. Diffusion refers to the movement of particles from an area of high concentration to an area of low concentration, and has no direct implication on sol stability.

Identify the correct method

Finally, consider the addition of electrolyte. The addition of an electrolyte engine can disrupt the balance, leading to aggregation of particles, which means destroying the sol. As electrolytes are charged particles, they can effectively neutralize the charge on the colloidal particles that gives them stability and stops them from aggregating.

Key concepts

Addition of Electrolyte

When we talk about the addition of an electrolyte to a colloid, we are referring to introducing charged particles into the colloidal system. This process is crucial because these charged particles can interact with the surface charges of the colloidal particles.
These surface charges, often at the same polarity, keep the colloidal particles from coming together—a phenomenon known as electrostatic stabilization. However, when electrolytes are added, they can

• neutralize the charge on the colloidal particles,
• reduce the repulsive forces among them, and
• allow the particles to come together or coalesce.

This coalescing or aggregation leads to the destabilization, and eventually to the precipitation or destruction, of the colloidal system. Thus, addition of electrolyte is a highly effective method to destroy or destabilize a sol, by counteracting the very forces that keep it stable.

Dialysis

Dialysis is a gentle yet scientifically powerful method used to purify colloidal solutions. It employs a semipermeable membrane to separate small, unwanted ions or molecules from larger colloidal particles. During the process:

• The colloidal solution is placed inside a dialysis bag or tube made of a semipermeable material.
• The surrounding medium, often water, facilitates the diffusion of smaller particles across the membrane.
• The semipermeable nature of the membrane prevents larger colloidal particles from leaking out.

This results in the removal of small impurities or ions, which might otherwise affect the properties of the colloid.
Interestingly, dialysis itself does not destabilize the colloid; instead, it purifies it. This can be beneficial for maintaining the desired stability of the colloid by removing unwanted small ions or impurities.

Colloid Destabilization

Colloid destabilization refers to the process by which the stable state of a colloidal system is disrupted, leading to the aggregation of its particles. Stability in a colloid is primarily maintained by:

• Electrical charges on the surface of the colloidal particles, and
• The solvation layer surrounding the particles.

When these factors are altered or removed, colloid destabilization occurs.
A few common methods that can lead to destabilization include:

• Adding electrolytes which neutralize the particles' charges.
• Changing the pH or temperature of the solution, which can affect the solvation layer.
• Introducing substances that physically or chemically interact with the sol, encouraging particles to aggregate.

Once destabilization initiates, particles begin to aggregate, leading to forms like flocs or precipitates. This highlights the importance of controlled conditions to maintain desired colloidal stability.