In an accident a container containing ethanol(s.g 0.789) falls down in a room of dimension 112(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.

Question

In an accident a container containing ethanol(s.g 0.789) falls down in a room of dimension 112(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 (37.1k points)

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.

(a) 4.73h

(b) 14.6h

(c) 5.87h

(d) 16.2h

The question was asked in exam.

My enquiry is from Diffusion in a Binary Gas Mixture topic in portion Diffusion in Solids and Molecular Diffusion in Fluids of Mass Transfer

1 Answer

Related questions

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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?

asked Sep 21, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

What is the value of the flux (kmol/m^3.s) of water vapor through a stagnant film of estimated thickness 1.5mm on the water surface?

asked Sep 21, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

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?

asked Sep 21, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

A sheet of Fe 1.0 mm thick is exposed to an oxidizing gas on one side and a deoxidizing gas on the other at 725°C. After reaching steady state, the Fe membrane is exposed to room temperature, and the C concentrations at each side of the membrane are 0.012 and 0.075 wt%. Calculate the diffusion coefficient (m^2/sec) if the diffusion flux is 1.4×10^-8kg/m^2-sec.

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 1 * 10 ^5 N/m^2, find molar concentration of oxygen

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 1 * 10 ^5 N/m^2, find overall mass density

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 1 * 10 ^5 N/m^2, find molar fraction of nitrogen

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 1 * 10 ^5 N/m^2, find the average molecular weight of the mixture

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 1 * 10 ^5 N/m^2, find mass fraction of oxygen

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

A water flows through a pipe at a velocity 2 m/s. The pressure gauge reading is 2 bar. The datum head is given to be 2 m. Find the piezometric head. (Assume all Bernoulli’s assumptions, Density of water = 1000 kg/m^3, g = 9.8 m/s^2).

asked Jan 30, 2022 in Fluid Mechanics by Charlotte (118k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

The gas A diffuses through non-diffusing B from point 1 to point 2. The total pressure is 2atm and yA1=0.1 and yA2=0.Then the ratio (dPA/dz)1/(dPA/dz)2 is

asked Sep 20, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

For a saddle siphon, the maximum operative head is 4.53 m. The width and height of the throat of the siphon are 5 m and 2.25 m respectively. The coefficient of discharge is 0.90. How many units are required to pass a flood of 350 cumecs? (Assume g = 10 m/s^2)

asked Sep 25, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

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 (37.1k points)

+1 vote

1 answer

Two horizontal steam mains with diameters 5 cm and 15 cm are to be laid in a boiler house that any mutual heat effect is precluded. The mains are at the same surface temperature of 500 degree Celsius whilst the ambient air is at 50 degree Celsius. Workout the ratios of the heat transfer coefficients

asked Sep 21, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

Find the permeability if diffusivity is 2 units and solubility coefficient is 5 units assume all are in SI units.

asked Sep 21, 2022 in Mass Transfer by Julian (37.1k points)

+1 vote

1 answer

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 (37.1k points)

Chris · Answer 1 · 2022-10-12T23:28:35+0000

The correct answer is (a) 4.73h

Explanation: This is the case of diffusion of through non diffusing B.

                NA=DP/RTZ*ln⁡[(P-P1)/(P-P2)]

                                     NA=(2.567*10-5*1.013)/(0.08317*298.2*2.5*10-3)*ln⁡[(1.013-0.02244)/(1.013-0.02718)] = 2.01*10^-6 kmol/m^2.s=9.259*10^-5kg/m^2.s

                                 Amount of ethanol = 2*10^-3*1=0.002m^3=1.578kg

                               Time for evaporation= 1.578/9.259*10^-5=17042.87s=4.73h.

Please log in or register to answer this question.

1 Answer

Please log in or register to add a comment.

Related questions

Categories