M.Sc. (Semester IV) (CBCS) Examination Mar/Apr-2018
Physical Chemistry
SURFACE CHEMISTRY
Time: 2½ Hours
Max. Marks: 70
Instructions: Attempt in all five questions. All question carry equal marks. Section I is compulsory. Attempt any two questions from section II and two from section III Answer to all questions (from section II, III) should be written in the one answer book. Figures to the right indicate full marks.
Section-I
Q.1
Solve the following:
14
For a adsorption of gas on solid surface, the plot of logxm versus log P is linear with a slope equal to
Define specific surface area of solid.
"Negative adsorption is the phenomenon in which surface tension of liquid decreases with concentration of surfactant", state whether statement is true or false.
Name the catalyst used in hydrogenation of oil.
Indicate meaning heterogeneous catalysis.
What is Kraft temperature?
State the relation between the adhesion between two solid particles and surface free energy during sintering process.
If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is
Acute angle
Obtuse angle
900
00
A square frame of side 1 is dipped in a liquid soap when it is taken out of the liquid, a film is formed on it. If surface tension is then force acting on it is
"Mercury on flat solid surface takes spherical shape", why?
What is expanding pressure?
The angle of contact between a glass capillary tube of length 10 cm and a liquid is 900. If the capillary tube is dipped vertically in the liquid, then the liquid
Will rise in the tube
Will get depressed in the tube
Will rise up to 10 cm in the tube and will over flow
Will neither rise nor fall in the tube
"Sintering of metallic powers is carried out at melting point of metal". State whether this statement is true or false.
"A drop of water mixes homogeneously with the emulsion".
State whether emulsion is oil in water or water in oil.
Page 2 of 2
SLR-UF-221
Section-II
Q.2
What is critical micelle concentration Discuss conductivity method of determination of cmc of a surfactant.
For sodium dedocyl sulphate the free energy of micellization is -5.3 kcal mole-1 at 25 °C. The calorimetric heat of micellization is 0.5 kcal mole-1. Calculate entropy change of micellization.
07
Derive an equation for spreading coefficient on thermodynamic consideration. How spreading coefficient is determined? Comments on the spreading of a liquid on the surface of other liquid using spreading coefficient.
07
Q.3
Derive Kelvin equation which relates the vapour pressure inside and outside droplet of liquid with its surface tension.
07
Describe Langmuir-Adam Surface pressure balance and its application in studying physical states of monomolecular films of surfactant prepared on surface of water.
07
Q.4
Derive Langmuir adsorption isotherm and explain its advantages and disadvantages.
07
What is point B method? Discuss determination surface area of the solids by using this method.
The adsorption experiment was carried at 77K by using 7.85 gm of iron oxide. The values of intercept and slope of the BET plot are 5X10-4 mL/S and 3.85X10-2 mL/s/bar. Calculate the specific surface area of catalyst. (The cross sectional area of nitrogen is 16.2 A0)
07
Section-III
Q.5
Discuss the property surface tension of liquid. Calculate the surface tension of alcohol which has risen to a height of 0.028 metre in a capillary of 0.2 mm diameter at 200C. The density of alcohol is 0.789 kgm-3.
05
Write Young and Laplace's equation with usual notations. Show that for the spherical interface the difference in pressure is given by the equation,
05
State and explain Trube's rule of lowering of surface tension of water by the fatty acids or alcohols.
04
Q.6
What is surface excess? Derive Gibb's adsorption equation.
05
Discuss theories of emulsification.
05
Explain the terms cohesion and adhesion energy of the liquids in terms of the surface tension.
04
Q.7
Write a note on any Three of the following.
14
Characteristics of satisfactory detergent
Preparation of organic nanoparticles
Herkins-Jura equation
Sintering of metallic powders