Problem 65 - A Complete Resource Book in Chemistry for JEE Main

Question

An emulsifier is a substance which (a) stabilizes the emulsion (b) coagulates the emulsion (c) retards the dispersion of liquid in liquid (d) causes homogenesis of emulsion

Step-by-Step Solution

Answer

(a) stabilizes the emulsion

Step 1: Understand the Role of an Emulsifier

An emulsifier is a substance that helps stabilize an emulsion, which is a mixture of two immiscible liquids (usually oil and water). Emulsifiers work by reducing surface tension at the interface between the liquids, allowing them to mix more effectively.

Step 2: Analyze the Options

Consider each option given in the problem: (a) Stabilizes the emulsion (b) Coagulates the emulsion (c) Retards the dispersion of liquid in liquid (d) Causes homogenesis of emulsion. Emulsifiers do not cause coagulation (b), as that would separate the mixture, nor do they retard dispersion (c). Homogenesis (option d) is not a recognized process related to emulsifiers.

Step 3: Choose the Correct Option

The correct role of an emulsifier is to stabilize emulsions, preventing the separation of the mixed liquids. Thus, option (a) stabilizes the emulsion, aligns with the function of an emulsifier.

Key Concepts

Emulsion

An emulsion is a type of mixture where two liquids, typically oil and water, are combined. However, these two liquids naturally do not mix well. Imagine trying to mix oil and vinegar in a salad dressing. The two liquids may blend temporarily, but soon they start to separate. An emulsion allows these two immiscible liquids to stay mixed together in a stable form.
Emulsions are found in common items like mayonnaise, lotions, and even some medications. To create an effective emulsion, one needs to stabilize the mixture, which can be achieved through the use of an emulsifier.

Immiscible Liquids

Immiscible liquids are liquids that do not naturally mix or dissolve in each other. Water and oil are classic examples. When you pour oil into water, the oil fl oats on top of the water, forming distinct layers.
Each liquid has different properties that prevent them from forming a solution. Immiscibility often comes from the lack of attraction between the molecules of the different liquids.

• Oil is hydrophobic (water-fearing), meaning it repels water.
• Water, on the other hand, is polar and only mixes well with other polar substances.

This natural resistance to mixing is what creates the challenge in making stable emulsions, which is where emulsifiers come into play.

Surface Tension

Surface tension refers to the force that acts on the particles at the surface of a liquid. It's like an invisible film that makes it difficult for the liquid to spread out. This property can keep liquids separated and is critical when mixing immiscible liquids.
In the context of emulsions, reducing surface tension between two immiscible liquids is necessary for them to mix. The way to achieve this is by adding an emulsifier. Emulsifiers lower this surface tension at the interface, allowing the two liquids to blend more easily and stay mixed for longer periods of time.

Emulsion Stabilization

Stabilizing an emulsion is crucial to maintaining its uniformity. Without stabilization, the two immiscible liquids would separate over time, reverting to their natural state. An emulsifier aids in this process by firmly positioning itself between the oil and water molecules.

• Emulsifiers have a hydrophilic (water-loving) head and a hydrophobic (oil-loving) tail.
• This dual nature allows them to bridge the gap between the water and oil, effectively keeping them together.
• The result is a stable blend, preventing the emulsion from breaking apart into separate layers.

By understanding the role of emulsifiers and surface tension, we obtain a clearer picture of how various everyday products maintain their consistency and effectiveness.