Surface Chemistry VVI Questions

 

 

Surface Chemistry Subjective Question 

“Q.1. What are Enzymes ?

Ans – Enzymes are complex organic nitrogenous compounds with high molecular masses. Enzymes are found in living cells of plants and animals. They form colloidal solutions in water. Enzymes are vital for biological processes. Without them, the life processes would be very slow and sluggish. for example, if there were no enzymes in our digestive system it would take us so years to digest a single meal.

 

Q.2. Define ‘Peptization’.

Ans – This is the process of converting freshly prepared precipitate into colloidal sol by shaking it with the dispersion medium in the presence of small ammount of electrolyte. The electrolyte added is called peptising agent.

 

Q.3. What is Tyndall effect ? Discuss.

Ans – Tyndall effect: On placing a homogenous solution (placed in dark) in the direction of light, it appears clear and if it is observed from a direction at right angles to the direction of light beam, it seems perfectly dark.

Colloidal solutions viewed in the same way may also appear reasonably clear or translucent by the transmitted light but they show a mild to strong opalescence, when viewed at right angles to the passage of light, i.e., the path of the beam is illuminated by bluish light. Or say when light falls on sol, sol absorbs the light and scatter it. This scattering of light is called Tyndall effect. 

Tyndall effect is observed only when the following two conditions are satisfied.

(1) The size of colloidal particles should not be much smaller than wavelength of incident light.

(2) The refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude.

 

Q.4. Give two methods for the preparation of colloids.

Ans – Two methods for the preparation of colloids;

(1) Condensation method – In these method, small particles of dispersed phase are condensed suitably to be of colloidal size.

(2) Dispersion method – In this method, larger particles of a substance are broken into smaller particles of colloidal size.

 

Q.5. Write in short : Brownian movement

Ans – Brownian movement – The zig-zag movement of colloidal particles in the dispersion medium is called brownian movement.”

Surface Chemistry Objective Question

“Q.1. Which gas is absorbed strongly by charcoal ?

(a) CO

(b)  NH3  

(c) NCl3

(d) H2

Ans – (b) NH3

 

Q.2. A catalyst is a substance which ;

(a) Increases the equilibrium concentration of the product

(b) Changes the equilibrium constant of the reaction 

(c) Shortens the time to reach equilibrium

(d) Supplies energy to the reaction 

Ans – (c) Shortens the time to reach equilibrium.

 

Q.3. Which one of the following is lyophilic colloid ?

(a) Milk

(b) Gum

(c) Fog

(d) Blood

Ans – (b) Gum

 

Q.4. Statement 1 ;- Physical adsorption is reversible.

Statement 2 ;- Chemical adsorption is also reversible

(a) Both the statements are true and statement 2 is correct explanation of statement 1

(b) Both the statements are true, but statement 2 is not the correct explanation of statement 1

(c) Statement 1 is true, but statement 2 is false

(d) Statement 1 is false, but statement 2 is true.

Ans – (c) statement 1 is true, but statement 2 is false