Fick’s law is given by the formula
Explanation: Experimental evidences shows that molecular diffusion is goverened by the empirical relation suggested by Fick.
Figure shows equimolal diffusion between species B and C. Identify the correct molar diffusion rate
Explanation: Equimolal diffusion between species B and C of a binary gas system implies that each molecule of component B is replaced by each molecule of constituent C.
What is the unit of diffusion coefficient?
Explanation: D = – N/ (d C/ d x).
What is the molecular weight of Sulphur-dioxide?
Formula of Sulphur-dioxide is SO 2.
What is the molecular volume of air at normal boiling point?
Explanation: Air contains some dust particles due to which its molecular volume decreases by a small factor.
What is the value of Schmidt number for hydrogen?
Explanation: Schmidt number = v/D.
Estimate the diffusion coefficient for ammonia in air t 25 degree Celsius temperature and one atmospheric pressure.
For ammonia,
Molecular weight = 17
Molecular volume = 25.81 cm3/gm mole
For air,
Molecular weight = 29
Explanation: D = 0.0043 T 3/2/p t (V b1/3 + V c1/3) 2 [1/M b + M c] ½.
Estimate the diffusion coefficient of carbon monoxide through air in which the mole fractions of each constituents are
O 2 = 0.18
N 2 = 0.72
CO = 0.10
The gas mixture is at 300 K and 2 atmosphere total pressure. The diffusivity values are
D CO = 18.5 * 10 -6 m2/s at 273 K, 1 atm
D CN = 19.2 * 10 -6 m2/s at 288 K, 1 atm
The subscripts C is carbon monoxide, O is oxygen and N is nitrogen
Explanation: (T 1/T 2) 3/2 (p 2/p 1) = D 1/D 2.
What is the molecular weight of Sulphur-dioxide?
Explanation: Formula of Sulphur-dioxide is SO 2.
The dimension of diffusion coefficient is given by
Explanation: Unit is m2/s
For what kind of mixtures DAB=DBA holds?
Explanation: None.
In the expression for molar flux NA=(NA+NB)CA/C – DABdCA/dz, the terms representing bulk flow and molecular diffusion are, respectively
Explanation: None.
Consider loss of ethanol vapor by diffusion from a half-filled open test tube. At what point in the diffusion path will the contribution of the bulk flow term to the molar flux be maximum?
Explanation: At the liquid-gas interface concentration will be maximum.
Bulk liquid is not a part of the diffusion path.
A reaction 3A+2B+C=1.5D+E occurs in a reactor at steady state. What will be the value of the flux ratio NA/ND
Explanation: NA/ND= (rate of disappearance of A)/(rate of appearance of D)
= -3/1.5
= -2.
For a component A of a mixture, concentration as a function of x is given:
CA=5e-10x (x is in cm and CA in mol/liter)
Calculate the value of diffusion velocity (m/s)of the component A at the point x=0, if diffusivity of A in the mixture is 2.567*10-5m2/s.
Explanation: By Fick’s law, JA=(-)DAB*dC/dx
CA(uA-U)= (-)DABdC/dx…………1
Diffusion velocity= (uA-U)=(-DABdC/dx)/CA
dC/dx = -50e-10x
CA= 5 mol/lit
Put all the values in equation 1.
A sheet of Fe 1.0 mm thick is exposed to a 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 (m2/sec) if the diffusion flux is 1.4×10-8kg/m2-sec.
Explanation: Convert from wt% to kg/m3 .
Concentration in kg/m3=[C1/(C1/ρ1+C2/ρ2)]*1000
0.012% and 0.075% in kg/m3 are 0.270 and 1.688 respectively.
Putting all the values in the equation JA=(-)DABdC/dx.
At which condition molar flux with respect to a stationary observer and with respect to a observer moving with molar average velocity?
Explanation: In a very dilute solution, the contribution of the bulk flow term becomes negligible.
NA= (NA+NB)CA/C – DABdCA/dz (general equation)
(NA+NB)CA/C =0 (in dilute solution)
NA= -DABdCA/dz = JA.
Which among the following is the statement of the ‘Fick’s Law’?
Explanation: None.
Fick’s law is given by the formula
Experimental evidences shows that molecular diffusion is goverened by the empirical relation suggested by Fick.
In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1mm into the surface of the titanium slab is 0.25kg/m3 and at 3mm the concentration is 0.68kg/m3. The rate at which the carbon is entering into its surface is 1.27*10-9kg/m2.s. calculate the value of diffusion coefficient of carbon.
Explanation: J=-D(∂C/∂x)
∂C/∂x= Δc/Δx=(0.25-0.68)/(0.003-0.001)=-215kg/m4
1.27*10-19kg/m2.s= -D*(-215kg/m4)
D=5.91*10-12m2/s.
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Test | 20 questions | 10 min
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Test | 10 questions | 10 min
Test | 10 questions | 10 min
Test | 20 questions | 20 min