This set of Bioseparation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Mass Transfer – Molecular Diffusion in Liquid Medium”.
1. Which separation process involves transport phenomenon?
a) Heat transfer, mass transfer
b) Fluid flow, mass transfer
c) Heat transfer, fluid flow
d) Heat transfer, mass transfer, fluid flow
View Answer
Explanation: The bioseparation processes are either isothermal or nearly isothermal in which the fluid flow is one of the significant process of bioseparation which involves transport phenomenon. The mass transfer is the most important transfer process in bioseparation. The heat transfer has significance in chemical separations.
2. Is movement of scent from one end of the room to other, an example of fluid flow?
a) True
b) False
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Explanation: The movement of scent from one end of the room to other is an example of mass transfer. Although fluid flow also deals with transfer of material but mass transfer mainly deals with transport of species within a medium or from one medium to another medium.
3. What are the types of mass transfer depending on the stationary and mobile phase?
a) Molecular diffusion, connective mass transfer
b) Molecular diffusion, purely diffusive mass transfer
c) Molecular diffusion
d) Connective mass transfer
View Answer
Explanation: The mass transfer is of two types depending on the stationary and mobile phase of the system and they are molecular diffusion also known as purely diffusive mass transfer and connective mass transfer. Molecular diffusion involves transport of molecules from region of higher concentration to the region of lower concentration. Connective mass transfer takes place in flowing fluid, when the flow of fluid is turbulent.
4. Which law will express molecular diffusion?
a) Fick’s second law
b) Mass conservation law
c) Fick’s first law
d) Energy conservation law
View Answer
Explanation: Molecular diffusion is the process which leads to distribution of chemical species for to attain uniformity with time. It can be expressed by Fick’s first law of diffusion which states that the diffusion of molecules occur in the response to the concentration gradient which is expressed as change in the concentration of the solution with change in position of molecule.
5. What is the equation of Fick’s first law of diffusion?
a) JA = -DAB(\(\frac{dCA}{dx}\))
b) JA = DAB(\(\frac{dCA}{dx}\))
c) JA = -(\(\frac{dCA}{dx}\))
d) JA = (\(\frac{dCA}{dx}\))
View Answer
Explanation: The equation for Fick’s law is JA = -DAB(\(\frac{dCA}{dx}\)) where, JA is the flux of A in B (Kg-moles/m2.s), DAB is the diffusivity of A in B (m2/s), CA is the concentration of A (Kg-moles/m2.s), x is length along direction of diffusion (m).
6. Which equation represents the steady state connective mass transfer in a transfer zone within a flowing fluid?
a) NA = kA – ΔCA
b) NA = kA ΔCA
c) NA = -kA ΔCA
d) -NA = kA ΔCA
View Answer
Explanation: The equation for connective mass transfer is NA = kA ΔCA where, NA is the flux of A, kA is the mass transfer coefficient of A within the transfer zone, ΔCA is the concentration difference across transfer zone. The flux of the solute is due to combination of molecular diffusion and the eddy diffusion.
7. The transport of an antibiotic from a solution to the surface of an ion-exchange resin is an example of ____________
a) fluid flow
b) heat transfer
c) molecular diffusion
d) connective mass transfer
View Answer
Explanation: Molecular diffusion in liquid occurs due to movement of molecule from one position to other; the movement takes place when the high energy of molecule breaks the bonds between other molecules which lead to movement of molecules.
8. The molecular diffusion in liquid medium is significantly slower than that in a gaseous medium.
a) True
b) False
View Answer
Explanation: The molecular diffusion takes place because of the thermal motion of the molecules. The thermal motion proceeds maximum in gases and lower in liquid and these differences are accounted by the nature of the thermal motion in the mediums. Hence, diffusion in liquid medium is slower than gaseous medium.
9. What is referred as equimolar counter–diffusion, when the molecular diffusion in amino acid and water gives certain flux value?
a) Jamino acid = Jwater
b) Jamino acid = -Jwater
c) Jamino acid = Jamino acid – Jwater
d) Jamino acid = Jamino acid
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Explanation: The equimolar counter-diffusion means that the direction of molar flux of the amino acid is same in the opposite direction of the flux of water. The diffusion coefficient of amino acid and the water becomes same and the molar concentration becomes constant.
10. The diffusion which occurs due to the thermal motion in the medium is called ___________
a) Molecular
b) Brownian
c) Turbulent
d) Connective
View Answer
Explanation: Molecular diffusion occurs due to thermal motion. Brownian diffusion occurs due to random movement of particle in bulk, the movement is independent of the medium. Turbulent diffusion occurs due to external stirred media in which the mass transfer occurs at huge level when the medium volume is displaced.
Sanfoundry Global Education & Learning Series – Bioseparation Technology.
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