Practicing Success

Target Exam

CUET

Subject

Chemistry

Chapter

Physical: Surface Chemistry

Question:

Emulsion: These are liquid-liquid colloidal systems, i.e., the dispersion of finely divided droplets in another liquid. If a mixture of two immiscible or partially miscible liquids is shaken, a coarse dispersion of one liquid in the other is obtained which is called emulsion. Generally, one of the two liquids is water. There are two types of emulsions. (i) Oil dispersed in water (O/W type) and (ii) Water dispersed in oil (W/O type).

In the first system, water acts as dispersion medium. Examples of this type of emulsion are milk and vanishing cream. In milk, liquid fat is dispersed in water. In the second system, oil acts as dispersion medium. Common examples of this type are butter and cream.

Emulsions of oil in water are unstable and sometimes they separate into two layers on standing. For stabilisation of an emulsion, a third component called emulsifying agent is usually added. The emulsifying agent forms an interfacial film between suspended particles and the medium. The principal emulsifying agents for O/W emulsions are proteins, gums, natural and synthetic soaps, etc., and for W/O, heavy metal salts of fatty acids, long chain alcohols, lampblack, etc.

What is the difference between vanishing cream and cold cream?

Options:

Both are examples of oil-in-water emulsions

Vanishing cream is an oil-in-water emulsion whereas cold cream is a water-in-oil emulsion

Vanishing cream is a water-in-oil emulsion whereas cold cream is anoil-in-water emulsion

Both are examples of water-in-oil emulsions

Correct Answer:

Vanishing cream is an oil-in-water emulsion whereas cold cream is a water-in-oil emulsion

Explanation:

Vanishing cream is an oil-in-water emulsion, implying that the dispersion medium is water and the dispersed phase is oil. Cold cream is a water-in-oil emulsion, implying that the dispersion medium is oil and the dispersed phase is water.