In the previous question if the floor has micro pores and water penetrates the floor at a constant rate of 0.1kg/m^2h, what will be the time required for the water layer to disappear?

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In an accident a container containing ethanol(s.g 0.789) falls down in a room of dimension 1*1*2(all in m). Ethanol forms a layer of 2mm. Ethanol vaporizes and diffuses through a stagnant film of air of thickness 2.5mm. What will be the time required for the water layer to disappear completely. The diffusivity of ethanol in air is 2.567*10^-5 m^2/s. the total pressure is 1.013 bar and the pressure of ethanol in bulk air is 0.02244 bar and at the ethanol-air interface is 0.02718bar. The temperature is 25.2°C.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Oxygen diffuses through a stagnant layer of air, 1mm thick, ambient temperature 28°C and 1atm total pressure. The partial pressure of oxygen on two sides of layer is P1=0.9atm and P2=0.1atm respectively. Calculate the value of Molar flux (in mol/m^2.s) with respect to an observer moving with molar average velocity. Calculate this value at the end of the path where P2=0.1atm. Use R=8.205*10^-5m^3atmK^-1mol^-1.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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A cylinder of sulfur is kept in a large volume of stagnant air for sublimation. How much time will be required for its complete sublimation?

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In order to prepare Lithium nitride, air is passed gently over a reactor. Suppose that Nitrogen diffuse to a length 5cm before getting reacted with Lithium. Nitrogen reacts with lithium quickly so that partial pressure of Nitrogen at that point is 0. Reactor is a cylinder of length 10cm and diameter 2cm. Assume air to be a mixture of Nitrogen and Oxygen only. The temperature is 298K and total pressure 1atm. Diffusivity of N2 in O2 is 2*10^-5m^2/s. Calculate the Molar flux (mol/m^2.s) of N2 at a distance of 2.5cm from the top with respect to an observer moving with twice the mass average velocity a direction towards the liquid surface. (R=8.205*10^-5m^3atmK^-1mol^-1). Assume z=0 at the top of the reactor.

asked Sep 20, 2022 in Mass Transfer by Julian (38.2k points)

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A tapered tube of length 8cm and end diameters 2cm and 4cm connects two vessels containing mixtures of A and B. if the tapered tube is replaced with a cylindrical tube of diameter 6cm, what will be the required length of the cylindrical tube to maintain the same flow rate as in the previous case?

asked Sep 20, 2022 in Mass Transfer by Julian (38.2k points)

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A binary liquid mixture is separated by distillation process. The more volatile A vaporizes while less volatile B gets transported in opposite direction. Latent heat of vaporization of A and B is 0.5unit and 1unit respectively. What will be the relation between molar flux of A and B

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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For a gas mixture (A+B) equimolar counterdiffusion takes place. Which among the following statements are correct for molar flux?

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The molar average velocity of the components in a binary mixture in which they are in equimolar counter diffusion is

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In the previous question what will be the value of flux (mol/m2.s) with respect to a stationary observer?

asked Sep 20, 2022 in Mass Transfer by Julian (38.2k points)

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In a binary gas mixture containing A and B, If NA=-2NB, what will be the expression for NA?

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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In sulphuric acid plants dry air is used for burning of sulphur. Air is dried in contact with concentrated Sulphuric acid. Moisture diffuses through a layer of air, reaches the surface and gets absorbed in it. Here air is said to be non-diffusing were as moisture is diffusing. Which of the following statements are correct?

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Two large vessels containing gaseous mixture of A and B at different concentrations but at the same total pressure are connected by a tapered tube of length 15cm and end diameters 1cm and 4 cm. what should be the diameter of a cylindrical tube of the same length that allows the same rate of transport of A?

asked Sep 20, 2022 in Mass Transfer by Julian (38.2k points)

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Find the flux of A ( xA= 0.2) if Total flux is 5 mol/sq.m sec and J flux of A is 2 mol/sq.m sec.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find J flux of A ( xA = 0.5) if the total N flux is 6 mol/sq.m sec and N flux of A is 3 mol/sq.m sec.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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If all the components except 1 of the multicomponent diffusing mixture are inert, then what will be the expression for Diffusivity of component 1 in the mixture?

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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At which point of the following locations in the tapered tube of the previous problem is the magnitude of the flux maximum?

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Sublimation of a long cylinder made of napthelene occurs in a large volume of stagnant air. The time required for its complete sublimation is

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find the time taken to dry 50% to 40% of moisture (dry basis) if critical moisture content is 30%. If the weight of the wet solid is 5 kg and the product of area and the constant rate is 0.5 kg/min.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find the activated diffusivity of carbon if energy of activation is 6 kJ; the value of constant diffusivity is 2.5 sq.m/sec. (Hint: the value of exponential of (-6/RT) is 2.55)

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find the change in concentration for a steady state equimolar counter diffusion if D(AB)= 6 sq.m/sec, the change in distance is 2 m and the N flux of A is 5 mol/sq.m sec.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find the total flux for a particle A and B in a steady state if flux of A and B is 2.44 and 4.44 mol/sq.m sec.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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What will be the values of the diffusivities (in cm^2/s) at the mean gas-film temperature?

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Consider steady-state equimolar counterdiffusion through the converging-diverging tube. Given: r1=1cm; r2=2cm; NA=10^-6 kmol/m^2.s at the vessel 1 end of the tube. The rate of transport of B at the vessel 2 end of the tube is

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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For two particles at steady state collision of A and B, J flux of A is 2 mol/sq.m sec find the J flux of B.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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Find the diffusivity of AB in sq.m/sec if N flux of A 5 mol/sq.m sec, concentration difference is 2mol/cu.m and distance is 3 m.

asked Sep 21, 2022 in Mass Transfer by Julian (38.2k points)

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