Mass Transfer II - Semester Exam Question

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Mass Transfer II - October 1998

Part A(20 X 2 = 40)

1. What is meant by differential distillation?
2. Draw a equilibrium diagram and boiling point diagram for an azeotropic binary system.
3. Raoult's law applies to the __________ and Henry's law applies to the _________.
4. What is relative volatility?
5. What is Murphree tray efficiency?
6. What is meant by constant molal overflow?
7. Define the term ''minimum reflux ratio''.
8. Panchan-Savarit method analyses the fractionating equipment based on _____________.
9. What is stripping factor?
10. Draw a neat sketch of packed absorption tower.
11. Write down the properties of a good packing for an absorption tower.
12. Write few industrial application of absorption.
13. What is a plait point?
14. What is selectivity? Selectivity of solvent used in extraction should be ____________.
15. What are the factors which affect a leaching operation?
16. Explain the terms extraction and leaching.
17. What are the desirable properties of an industrial adsorption?
18. What is meant by a break through curve for adsorption?
19. What are the various types of dialysis?
20. Write the principle of Ion-exchange.

Part B(5 X 12 = 60)

21. (a) (i) Differentiate between flash distillation, differential distillation and rectification. (4)

    (ii) Describe with a neat sketch the working of a batch distillation unit and state its fields of application. (8)

    Or

    (b) (i) Derive Rayleigh's equation. (3)

    (ii) A feed of 50 mole % hexane and 50 mole % octane is fed into a pipe still through a pressure reducing valve and then into a flash disengaging chamber. The vapor and liquid leaving the chamber are assumed to be in equilibrium. If the fraction of the feed converted to the vapor is 0.5, find the compositions of the top and bottom products. The following table gives the equilibrium data for this system. (9)

Mole fractions of hexane in liquid X	1.00	0.69	0.40	0.192	0.045	0.00
Mole fractions of hexane in vapour Y	1.00	0.932	0.78	0.538	0.1775	0.00

 

22. (i) Describe the method of estimation of the number of theoretical plates using Panchan-Savarit method (9)

(ii) Explain the effect of quality of feed in distillation calculation. (3)

Or

(b) A continuous fractionating column operating at atmospheric pressure is to separate a feed containing 30% CS₂ and 70% CC1₄ into an overhead product of 95 % CS₂ and a bottom product of 95 mole % CC1₄. The feed enters as a liquid at its boiling point. Assuming an overall plate efficiency of 70% and a reflux ratio of 3:1 estimate the number of plates needed. All the compositions are in mole %.

Equilibrium data:

x	0.0296	0.0615	0.258	0.39	0.532	0.663	0.758	0.86
y	0.0823	0.1555	0.494	0.634	0.747	0.830	0.880	0.932

 

23. (i) In a graph, show the relative positions of equilibrium and operating times for absorption and stripping.

(ii) What are the types of packing? Explain them with suitable examples.

Or

(b) If an air- ammonia mixture containing 5% ammonia by volume is absorbed in water using a packed tower at 20^oC and 1 atm pressure to recover 98% ammonia and the inert gas flow rate is 1200 kg/hr.m2, Determine

(i) minimum mass velocity of liquid and

(ii) number of transfer units using 1.25 times the minimum liquid flow rate. The equilibrium relationship for the system is given by y =1.154 x where x and y are expressed in mole fraction units.

24. (a) 1000 kg/hr of a water-dioxane solution containing 20% dioxane is to be continuously and counter currently extracted with benzene at 25^oC to recover 80% dioxane. Water and benzene are essentially insoluble and the equilibrium distribution of dioxane between them are as follows:

wt % of dioxane in water (100 x)	5.1	18.9	25.2
wt % of dioxane in benzene (100 y)	5.2	22.5	32.0

Determine the number of stages required if the solvent rate is 1.5 times the minimum benzene is used Benzene is free from dioxane.

Or

(b) (i) Describe the Bollmann extractor used in leaching operation.

(ii) Write briefly about selection of solvent liquid -liquid extraction.

25. (a) Explain the following processes and state their Industrial applications

    (i) dialysis and

    (ii) Reverse osmosis.

    Or

    (b) (i) Distinguish between the two types of adsorption phenomena out their essential features. (6)

    (ii) Explain briefly the following: adsorption isotherm and adsorption hysterisis. (6)

Last Modified on: 04-Feb-2022

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