Register Number: _________________Answer all the QuestionsPART A (10 x 1 = 10 Marks)Objective Types & Fill in the Blanks1.A naphthalene hemisphere is placed on a glass plate and a naphthalene ball of identical diameter is kept suspended in the stagnant air in two large rooms of same volume. The respective shapes of the balls are maintained while they sublime and reduce in size. Which of the following statements are true? (K3)

a)They take the same time for complete sublimationb)The sphere disappears first

c)The hemisphere disappears firstd)No sublimation occurs

2.The unit of diffusivity in SI system is __________ (K1)

3.Which of the following diffusion phenomenon can be explained by a hopping mechanism? (K3)

a)Knudsen diffusionb)Surface diffusion

c)Multicomponent diffusiond)No diffusion

4.The ratio between mass flux and molar flux is __________ (K2)

5.Which of the following mechanism is observed in breathing process? (K2)

a)Knudsen diffusionb)Surface diffusion

c)Multicomponent diffusiond)No diffusion

6.__________ (mass transfer operation) is an example for equimolar counter diffusion. (K2)

7.If the mass transfer is expressed in terms of mass transfer coefficient, the driving force should be (K3)

a)Concentration gradient at the interfaceb)Concentration gradient at the interface and the bulk

c)Interfacial concentrationd)Bulk concentration

8.The driving force of momentum transfer is __________ (K1)

9.For gas absorption from a bubble in steady rise through a stagnant liquid, which of the following theories is more appropriate? (K2)

a)Surface renewal theoryb)Film theory

c)Penetration theoryd)Film penetration theory

10.__________ = Driving force/Resistance (K1)

PART B - [Answers not more than 40 words] (5 x 2 = 10 Marks)Short Answer Questions

11.The species A diffuses through gas mixture A-B from point x=0, y=yo to x=l, y=y at temperature T and pressure P. The total pressure is now doubled, but the mole fractions, T and P remains same as before. What would be the fractional increase in the flux of A? (K2)

12.Equimolar counter diffusion occurs in binary mixture A-B through a spherical film of ineer diameter r and thickness t. The flux of A is NA at r. The flux through a flat film of same thickness is NB. What is the fractional increase in thickness if NA is greater than NB by 5%? (K3)

13.Classify mass transfer operations with suitable examples. (K1)

14.Define interphase mass transfer. (K1)

15.Write short notes on individual mass transfer coefficient. (K2)

PART C [Answers not more than 300 words] (3 x 10 = 30 Marks)[Question No. 16 is compulsory]

Q.no.Mark

16.Through the accidental opening of a valve, water has been spilled on the floor of an industrial plant in a remote, difficult to reach area. Estimate the time required to evaporate the water into surrounding quiescent air. The water layer is 1 mm thick and may be assumed to remain at constant temperature of 24C. The air is also at 24C and 1 atm pressure with an absolute humidity of 0.002 kg water vapour / kg dry air. The evaporation is assumed to take place by molecular diffusion through a gas film of 5 mm thickness. Diffusivity of water vapour in air is 0.259 sq. cm/s. (K3)10

17.a)Ethanol is diffusing through a water layer of 3 mm thickness at 20C. Diffusivity of alcohol in water is 520 m2/s. The concentrations on opposite sides of water film are 4% and 10% (w/w) alcohol respectively are 0.99 and 0.98 g/cc. Assume that water film is stagnant, estimate: (K3)(i) The flux of alcohol(ii) Concentration of alcohol in the middle of water film.10

(OR)

b)In O2-N2 mixture at 1 atm and 20C, the concentrations of O2 at two planes 2 mm apart are 20% and 10% (v/v) respectively. Calculate the rate of diffusion of O2 in kg/m2.s for the case N2 is non-diffusing. Diffusivity is 0.181 cm2/s. Calculate the rate of diffusion of O2 assuming equimolal counter diffusion. (K3)10

18.a) In an experimental study of absorption of ammonia by water in a wetted wall column, the overall gas phase mass transfer coefficient was 0.000272 kmol/m2.s.atm. At one point in the column, the gas contained 10% (v/v) ammonia and the liquid phase concentration was 0.0642 kmol NH3/m3 of solution. Process occurs at 20C and 1 atm. 85% of resistance to mass transfer lies in gas phase. If Henrys law constant is 0.00953 atm.m3/kmol, calculate the individual film coefficients and the interfacial composition. (K3)10

(OR)

b)At 20C, the solubility of ammonia in water is given by Henrys law p = 0.3672 C where p is in atm and C is in kmol/m3. A mixture of 15% ammonia-85% air by volume at 1 atm is in contact with an aqueous solution containing 0.147 M. Air velocity such that kg/kL = 0.9. Find the concentration of ammonia and partial pressure at interface. (K3)10

******************** All the Best *********************2