Answer:

Sol destruction refers to the process of converting a sol into a solid precipitate. This can be achieved through various methods, including dialysis, diffusion through semi-permeable membranes, addition of an electrolyte, and condensation. Among these methods, the correct answer is option 'C' - addition of an electrolyte.

Explanation:

Addition of an electrolyte:
When an electrolyte is added to a sol, it disrupts the stability of the colloidal particles and causes them to stick together. This phenomenon is known as coagulation or flocculation. The added electrolyte neutralizes the charge on the colloidal particles, resulting in the formation of larger aggregates that eventually settle down as a precipitate.

The process of sol destruction by addition of an electrolyte can be explained by the following steps:

1. Neutralization of charge:
The colloidal particles in a sol carry a net charge, either positive or negative, due to the adsorption of ions on their surface. When an electrolyte is added, the ions from the electrolyte interact with the charged particles, neutralizing their charge. This reduces the electrostatic repulsion between the particles, allowing them to come closer.

2. Formation of aggregates:
As the particles come closer, the attractive forces between them become stronger than the repulsive forces. This leads to the formation of aggregates or clusters of particles. The aggregates continue to grow in size as more and more particles join them.

3. Precipitation:
The aggregates eventually become heavy enough to settle down under the influence of gravity, forming a solid precipitate. The precipitate separates from the liquid medium, resulting in the destruction of the sol.

Other methods:

- Dialysis: Dialysis is a process in which a sol is placed in a dialyzing bag or membrane and immersed in a suitable solvent. The smaller particles or ions can pass through the membrane, while the larger colloidal particles are retained. This method is used for the purification of sols but not for their destruction.

- Diffusion through semi-permeable membrane: Diffusion through a semi-permeable membrane is a process in which solute particles move from an area of higher concentration to an area of lower concentration through a membrane that allows only certain particles to pass. This method is not specifically used for sol destruction but for separation or purification purposes.

- Condensation: Condensation is a phase transition from a gas or vapor to a liquid or solid state. It involves the conversion of individual particles into a larger aggregate or droplet. While condensation can occur in the formation of sols, it is not a method specifically used for sol destruction.

In conclusion, the addition of an electrolyte is the method used for sol destruction by causing coagulation or flocculation of the colloidal particles, leading to the formation of larger aggregates that settle down as a precipitate.