Problem 150 - A Complete Resource Book in Chemistry for JEE Main

Question

Emulsion can be destroyed by (a) The addition of an emulsifier which tends to form an emulsion of the same type. (b) Freezing (c) Electrophoresis with a high potential (d) All of these

Step-by-Step Solution

Answer

The emulsion can be destroyed by all of these methods.

Step 1: Explanation of Emulsifier Addition

Emulsions are mixtures of two immiscible liquids, where one is dispersed in the other. Adding an emulsifier that promotes the formation of an emulsion of the same type typically stabilizes the emulsion rather than destroying it.

Step 2: Freezing Effect on Emulsions

Freezing can cause the water in an emulsion to crystallize, thereby causing separation of the two phases and destruction of the emulsion. This process can lead to the breaking of emulsions as the structure is disrupted.

Step 3: Electrophoresis with High Potential

Emulsions often carry an electric charge, and applying a high potential through electrophoresis can cause coalescence of the charged particles, thus breaking the emulsion. This is due to the migration and combination of charged droplets.

Step 4: Conclusion of Options

Considering all options, each choice listed can contribute to the destruction of an emulsion. Freezing changes physical state, while electrophoresis causes electrical disruptions, both leading to breakdown. Therefore, the correct answer is choice (d), "All of these."

Key Concepts

Emulsifier

In the world of chemistry, an emulsifier acts like a bridge between two competing sides: oil and water. Oils and water naturally repel each other and do not mix. An emulsifier is a special type of molecule that helps keep these immiscible liquids mixed together, forming a stable emulsion. It works by having one end that is attracted to oil (lipophilic) and the other end attracted to water (hydrophilic). Emulsifiers are commonly found in food and cosmetics. For example, in mayonnaise, an emulsifier such as lecithin from egg yolks helps to keep the vinegar and oil mixed without separating. Instead of breaking up an emulsion, an appropriate emulsifier makes it more durable. Conversely, selecting an incorrect emulsifier for the type of emulsion can actually destabilize it, but under typical circumstances, emulsifiers stabilize rather than destroy.

Freezing Effect on Emulsions

The freezing effect on emulsions refers to how cold temperatures can lead to the breaking of these mixtures. When an emulsion is exposed to freezing temperatures, the water component may crystallize. Ice crystals can grow and disrupt the finely balanced structure of the emulsion. This leads to the separation of the oil and water phases, causing a breakdown. The crystallization process changes the physical arrangement, and once thawed, the emulsion may not return to its original state. This is because the delicate balance between the two immiscible liquids has been disrupted irreversibly. For example, freezing a salad dressing may lead to a grainy texture once it is thawed, as the emulsion breaks.

Electrophoresis

Electrophoresis is a fascinating process used to move particles through a solution by applying an electric field. In the context of emulsions, this technique can be used to disrupt them. Many emulsion droplets carry an electrical charge. When a high potential is applied through electrophoresis, the charged droplets begin to move and migrate.

• This movement can cause droplets to come into contact and coalesce, leading to the breakdown of the emulsion.
• The high electric field essentially pushes these charged particles to a point where they merge and form larger droplets, ultimately causing separation.

Using electrophoresis to break emulsions is a method employed in various industrial processes where separating the components of an emulsion is necessary. It showcases the power of electrical influence on chemical mixtures.