Surface Chemistry Viva Questions and Answers

Surface chemistry deals with every kind of surface phenomenon. Surface chemistry studies the phenomenon occurring on the surfaces of substances. This is often very applicable in industries and everyday lives. The vital topics in surface chemistry are adsorption, catalysis, colloids, and emulsions. Surface chemistry prepares photocatalysts, batteries, fuel cells, etc. In this article, we will discuss the chemistry viva questions with answers.

Table of Content

• Aim

• Articles Required

• Theory

• Procedure

• Observations

• Result

• Precautions

• Viva Questions

• Summary

Aim

• Project on surface chemistry class 12.

• Elucidate the concepts of adsorption and absorption in surface chemistry.

• Explain the different types of adsorption.

Articles Required

• Beakers

• Glass rod

• Funnel

• Filter paper

• Burner

• Pestle mortar

• Tripod stand

Theory

Depending upon the interaction between the disperse phase and the dispersion medium, the colloidal solutions are classified into 2 types:

• Lyophilic sols

• Lyophobic sols.

1. Lyophilic Sols

The dispersed part features a great affinity for the dispersion medium in this colloidal solution. In such colloids, the dispersed phase isn't simply precipitated, and the sols are pretty stable. The solids obtained when evaporation could also be reconverted to the sol state by simply agitating them with the dispersion medium. Examples of lyophilic sols include sols of gum, gelatine, starch, proteins, and certain polymers in organic solvents. Such sols are known as reversible sols. Any solution with a higher viscosity ends up with a decrease in surface tension than the dispersion medium.

2. Lyophobic Sols

In this form of sols, disperse phase has very little affinity for the dispersion medium. These sols are comparatively less stable than lyophilic sols. These sols are simply precipitated (or coagulated) with the addition of small amounts of electrolytes, by heating or shaking. These are irreversible as their precipitated mass can not be brought back into the colloidal state by simply shaking them up with the dispersion media.

Examples of lyophobic sols include sols of metals and their insoluble compounds like sulfides and oxides. They have stabilising substances for preservation. If water is the dispersion medium, these are referred to as hydrophobic sols.

Procedure

• Take the sample in a mortar and add a few ml of DI (Distilled Water).

• Make a thin paste of sample and transfer it to a beaker.

• Add DI to the beaker and start heating the beaker until the water starts boiling.

• Continue the boiling for about 10 minutes and allow the beaker to cool at room temperature.

• Place the filter paper in the funnel.

• Filter the sample through filter paper and label the filtrate.

Result 

The colloidal solution of the sample is prepared. 

Precautions 

Following precautions must be taken while carrying out the experiment

• The apparatus used for preparing sol should be clean.

• For preparing sol, DI should be used.

• Continuous stirring of the content should be done properly.

Viva Questions 

Q1. What is a colloidal solution? Give an example.

Ans. A colloidal solution may be a “two-phase heterogeneous system during which a substance is distributed within the colloidal state (particles having a diameter between one to 1000 nm) in a medium”. The particles of the dispersed substance (of colloidal size) are known as the dispersed phase’, whereas the medium within which they're dispersed is termed the dispersion medium. For example, milk, butter, smoke, etc.

Q2. What is the size of colloidal particles?

Ans.  Between 1—100 nm.

Q3. Give two examples of positively charged sols.

Ans. Ferric hydroxide sol and aluminium hydroxide sol.

Q4. What is meant by the term dialysis?

Ans. The method of separating electrolytes from a colloid by means of diffusion of the former through an animal or vegetable membrane is termed dialysis.

Q5. What is the use of dialysis?

Ans. Dialysis is used for purifying colloidal solution. In the presence of excess electrolytes, the colloidal solutions get coagulated. When a colloidal sol containing impurities is kept in a parchment bag, the electrolytes pass through the membrane, while a parchment bag retains colloidal particles.

Q6. How can we make dialysis fast?

Ans. By circulating hot water, instead of cold water, in the container or applying an electric field across the dialyser.

Q8. What is coagulation?

Ans. Coagulation is a process of changing the colloidal state into an insoluble precipitate by inducing aggregation of colloidal particles.

Summary 

In this article, we have mentioned surface chemistry, the surface tension of lyophilic sols and lyophobic sols, and the surface tension of lyophilic sols. There are 2 forms of colloidal solutions. The viva questions and answers for surface chemistry practical class 12 are also discussed. The surface chemistry viva questions with answers are explained in this article.