Surface Chemistry Test - 19

The correct answer is Option C.

Lyophobic colloid is a colloidal dispersion whereby the dispersed phase is solvent hating .i.e little interaction between the dispersed phase and the continuous phase. Lyophobic colloidal particles are not readily solvated because the continuous phase prefers to interact with one another rather than be involved in solvating the dispersed particles. 
Casein (a milk protein), a lyophobic colloid present in milk acts as an emulsifying agent as it forms a protective layer around fat molecules dispersed in water. It is found in milk as a suspension of particles called "casein micelles" which show only limited resemblance with surfactant-type micelle in a sense that the hydrophilic parts reside at the surface and they are spherical.
 

The correct answer is option B.
Water in oil (w/o) type : In these emulsions, water is in the dispersed phase and oil is in the dispersion medium. For example: butter, cold cream etc. They are also called oil emulsions.

The correct answer is option  C
Emulsifying agent
Emulsification is the process which involves the preparation of emulsion.Generally, an emulsion is prepared by subjecting a mixture of the immiscible liquid to a distinct layer upon standing. To prevent the separation of layers and to get the stable emulsion, a small quantity of the third substance is added. This substance which stabilizes the emulsion is called an emulsifier.
 

The correct answer is Option B.
An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. 
Examples: Oil and water mixtures are emulsions when shaken together. The oil will form drops and disperse throughout the water. So, curd is not an emulsion.
 
Foam is a substance where air or gas bubbles are trapped inside a solid or liquid. 
Examples: Styrofoam, whipped cream, soap bubbles. So, mist is not a foam.
 
An aerosol is a colloid of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or not. An Example of natural aerosol is fog. Examples of artificial aerosols are dust, particulates, air pollutants and smoke.
 
Solid sol is a type of colloid of the form of one solid dispersed in another continuous solid. So, cake is not solid sol.

The colloidal dispersion of a liquid in a liquid is called emulsion.
In these systems, one liquid is dispersed in another  liquid immiscible with it.
For example, milk is an emulsion of oil in water. The particles of liquid fat are dispersed in water.
Cod Liver oil is an emulsion of water in oil. consists of particles of water dispersed in oil.

The correct answer is Option B
Milk is an emulsified colloid of Liquid is dispersed in liquid where liquid butterfat globules dispersed within a water-based solution.

The correct answer is option  D.
Milk is an emulsion with fat particles (globules) dispersed in an aqueous (watery) environment. The fat globules do not coalesce and form a separate layer (oil off or churn) because they are protected by a membrane layer which keeps the fat particles separate from the water phase.

The correct answer is Option B.
 Lecithin works as an emulsifier which stabilises the emulsion.

The correct answer is Option C.

'Vanishing cream' is a cream or ointment that leaves no visible trace when rubbed into the skin.
It is an  "oil in water" type emulsion. It contains potassium, ammonium, or sodium stearate with water and  free stearic acid, a hygroscopic ingredient such as glycerol, and a small amount of a fatty ingredient.
 

The correct answer is option C
Demulsification is the breaking of a crude oil emulsion into oil and water phases. 
Demulsification is used to separate various mixtures like water in oil and oil in water etc.
It completely separates the constituent liquids and hence is the reverse of emulsification.