This set of Bioseparation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Mass Transfer – Measurement and Estimation of Diffusivity”.
1. Which is the commonly used technique for experimental measurement of the diffusivity of a solute in a liquid medium?
a) Diffusion cell
b) Filtration chamber
c) Dryer
d) Crystallizer
View Answer
Explanation: The commonly used technique for experimental measurement of the diffusivity of a solute in a liquid medium is diffusion cell. The diffusion cell consists of two well mixed chambers which have same volume and are separated by a porous membrane. The chambers are filled with the liquid and the pores of the membrane are filled with that liquid and it helps in measurement of diffusivity.
2. How to obtain the diffusivity when the concentration of solute in the chambers of diffusion cell is based on the change in solute concentration with time?
a) DAB (\(\frac{\delta^2 C_A}{\delta x^2} + \frac{\delta^2 C_A}{\delta y^2} + \frac{\delta^2 C_A}{\delta z^2}\)) = \(\frac{\sigma C_A}{\delta t}\)
b) DAB = \(\frac{V\delta \tau}{2\varepsilon at}\) ln(\(\frac{{C_1} ^0 – {C^0}_2}{C_1 – C_2}\))
c) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
d) DAB = –\(\frac{V\delta \tau}{2\varepsilon at}\) ln(\(\frac{{C_1} ^0 – {C^0}_2}{C_1 – C_2}\))
View Answer
Explanation: The diffusivity of the solutes, when the concentration of solute in the chambers of diffusion cell is based on the change in solute concentration with time can be estimated using DAB = \(\frac{V\delta \tau}{2\varepsilon at}\) ln(\(\frac{{C_1} ^0 – {C^0}_2}{C_1 – C_2}\)) where, V is the volume of the chamber, δ is the thickness of the chamber, τ is the tortuosity of the membrane, ε is the porosity of the membrane, a is the area of the membrane, t is the time required by the solute to travel through the chambers, C1 is the solute concentration in chamber 1 and C2 is the solute concentration in chamber 2. “0” represents the initial value of time.
3. How to estimate the diffusivity of a solute in a liquid medium at a particular temperature?
a) Steady state experiments based on NA = kA ΔcA
b) Molecular diffusion
c) Mathematical correlation
d) Connective mass transfer
View Answer
Explanation: The diffusivity of a solute in a liquid medium at a particular temperature is estimated using mathematical correlation. The mathematical correlations link the estimated diffusivity with the solute and the properties of the liquid. Molecular diffusion and connective mass transfer is used to understand the transfer of material from one region to another. Steady state experiments are used to determine the mass transfer coefficient.
4. Which liquid properties correlate the diffusivity of solute in the liquid medium?
a) Pressure, surface area, viscosity
b) Diffusivity, viscosity, surface tension
c) Molecular weight, pressure, surface tension
d) Molar volume, molecular weight, viscosity
View Answer
Explanation: Molar volume, molecular weight, viscosity are the properties of liquid which correlate the diffusivity of solute in the liquid medium at a specific temperature. The flow of solute is dependent on the molecular weight of the solute, volume of solute and the viscosity of the liquid so that the flow of solutes in the liquid medium is maintained through the equilibrium.
5. State the correlation equation which is used to correlate the diffusivity.
a) Stokes-Einstein correlation, Wilke-Chang correlation, Polson correlation
b) Correlation coefficient, Wilke-Chang correlation
c) Diffusion coefficient, Polson correlation
d) Regression coefficient, Stokes-Einstein correlation
View Answer
Explanation: The Stokes-Einstein correlation, Wilke-Chang correlation, Polson correlation is used to estimate the correlation in diffusivity. The diffusion coefficient or diffusivity of particles which undergoes Brownian motion in a liquid is at uniform temperature when undergoes diffusion.
6. What is the equation for Stokes-Einstein correlation?
a) DAB (\(\frac{\delta^2 C_A}{\delta x^2} + \frac{\delta^2 C_A}{\delta y^2} + \frac{\delta^2 C_A}{\delta z^2}\)) = \(\frac{\sigma C_A}{\delta t}\)
b) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
c) DAB = –\(\frac{V\delta \tau}{2\varepsilon at}\) ln(\(\frac{{C_1} ^0 – {C^0}_2}{C_1 – C_2}\))
d) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
View Answer
Explanation: DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\)) is the equation which represents Stokes-Einstein correlation, where T is the absolute temperature, μ is the viscosity, VA is the solute molar volume at its normal boiling point.
7. What is the equation for Wilke-Chang correlation?
a) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
b) DAB = (\(\frac{9.40 × 10^{-15}T}{\mu V_A^{1/3}}\))
c) DAB = \(\frac{1.173 × 10^{-16}(\varphi M_B)^{1/2}T}{\mu V_A^{0.6}}\)
d) DAB = \(\frac{8.928 × 10^{-10}T (\frac{1}{n_+} + \frac{1}{n_-})}{(\frac{1}{λ_+} + \frac{1}{λ_-})}\)
View Answer
Explanation: DAB = \(\frac{1.173 × 10^{-16}(\varphi M_B)^{1/2}T}{\mu V_A^{0.6}}\) is the equation for Wilke-Chang correlation, where φ is the association parameter and has a value of 2.6 for water, MB is the molecular weight of the the liquid medium, DAB is the diffusivity, T is the absolute temperature, μ is the viscosity, VA is the solute molar volume at its normal boiling point.
8. What is the equation for Polson correlation?
a) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
b) DAB = \(\frac{1.173 × 10^{-16}(\varphi M_B)^{1/2}T}{\mu V_A^{0.6}}\)
c) DAB = \(\frac{8.928 × 10^{-10}T (\frac{1}{n_+} + \frac{1}{n_-})}{(\frac{1}{λ_+} + \frac{1}{λ_-})}\)
d) DAB = (\(\frac{9.40 × 10^{-15}T}{\mu V_A^{1/3}}\))
View Answer
Explanation: DAB = (\(\frac{9.40 × 10^{-15}T}{\mu V_A^{1/3}}\)) is the equation for Polson correlation where, MA is the molecular weight of the the liquid medium, DAB is the diffusivity, T is the absolute temperature, μ is the viscosity, VA is the solute molar volume at its normal boiling point.
9. Which equation will estimate the diffusivity of electrolytes?
a) Nernst-Haskell correlation
b) Stokes-Einstein correlation
c) Wilke-Chang correlation
d) Polson correlation
View Answer
Explanation: Nernst-Haskell correlation equation is used to estimate the diffusivity of electrolytes. In order to observe the diffusion of salts at low concentration, the diffusivity is estimated using empirical correlations which encounter the concentrations of the solute in the solution.
10. What is the equation for Nernst-Haskell correlation?
a) DAB = (\(\frac{9.96 × 10^{-16}T}{\mu V_A^{1/3}}\))
b) DAB = \(\frac{8.928 × 10^{-10}T (\frac{1}{n_+} + \frac{1}{n_-})}{(\frac{1}{λ_+} + \frac{1}{λ_-})}\)
c) DAB = \(\frac{1.173 × 10^{-16}(\varphi M_B)^{1/2}T}{\mu V_A^{0.6}}\)
d) DAB = (\(\frac{9.40 × 10^{-15}T}{\mu V_A^{1/3}}\))
View Answer
Explanation: DAB = \(\frac{8.928 × 10^{-10}T (\frac{1}{n_+} + \frac{1}{n_-})}{(\frac{1}{λ_+} + \frac{1}{λ_-})}\) is used to determine the diffusivity of electrolytes where, n+ is the valency of cation, n– is the valency of anion, λ+ is the ionic conductance of cation, λ– is the ionic conductance of anion, DAB is the diffusivity, T is the absolute temperature.
11. Calculate the diffusivity of lysozyme in water when the temperature is maintained is 25°C.
a) 2.16 × 10-12 m2/s
b) 2.16 × 10-10 m2/s
c) 1.16 × 10-10 m2/s
d) 1.16 × 10-12 m2/s
View Answer
Explanation: The diffusivity of the solute can be calculated using equation DAB = (\(\frac{9.40 × 10^{-15}T}{\mu V_A^{1/3}}\)) so the molecular weight of lysozyme is 14100 kg/kg-mole and the viscosity of water at 25°C is 0.001 Kg/m s. ∴ DAB = (\(\frac{9.40 × 10^{-15} × 298}{0.001 × 14100^{\frac{1}{3}}}\)) = 1.16 × 10-10 m2/s.
Sanfoundry Global Education & Learning Series – Bioseparation Technology.
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