This set of Bioseparation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Precipitate Formation – Set 2”.

1. Which is the limiting factor for the growth of precipitate particles?

a) Diffusion

b) Mixing

c) Nucleation

d) Convention

View Answer

Explanation: The growth of precipitate particles is limited by diffusion just after nucleation and the particles grow to a size defined by the fluid motion and it ranges from 0.1 μm to 10 μm for low as well as high shear fields.

2. Which rate order reaction was used for kinetics of uniform size particle in dispersion that is growing as dissolved solute diffuses to the particles?

a) First order reaction

b) Zero order reaction

c) Second order reaction

d) Pseudo first order reaction

View Answer

Explanation: The second order rate reaction describes the dispersion of particles of uniform size of growing particles dissolved solute and the initial rate of particle concentration decreases with time.

3. Who derived the second order rate reaction which described the initial rate of decrease of particle number concentration?

a) Juckes

b) Camp and Stein

c) Kolmogroff

d) Smoluchowski

View Answer

Explanation: The second order rate reaction was derived by Smoluchowski. Camp and stein derived equation for turbulent flow of solvents. Kolmogroff derived the model for micro-mixing. Juckes developed model for protein purification.

4. What is the equation derived by Smoluchowski?

a) \(\frac{dN}{dt}\) = K_{A}N^{2}

b) –\(\frac{dN}{dt}\) = K_{A}N^{2}

c) –\(\frac{dN}{dt}\) = K_{A}N

d) \(\frac{dN}{dt}\) = K_{A}N

View Answer

Explanation: The equation derived by Smoluchowski is –\(\frac{dN}{dt}\) = K

_{A}N

^{2}where, N is the number of mono-sized particles at a given time t and K

_{A}is the constant determined by the diffusivity where K

_{A}= 8πDL

_{mol}and L

_{mol}is the diameter of molecules.

5. Which equation has been verified experimentally by measuring the molecular weight of the precipitated protein?

a) M = M_{0}(1 + K_{A}N_{0}t)

b) M = M_{0}(1 – K_{A}N_{0}t)

c) M = M_{0}(K_{A}N_{0}t)

d) M = (1 + K_{A}N_{0}t)

View Answer

Explanation: The equation M = M

_{0}(1 + K

_{A}N

_{0}t) is used for measurement of molecular weight of the precipitated protein. M is the molecular weight, M

_{0}is the initial weight, K

_{A}is the constant determined by the diffusivity, N

_{0}is the initial number of mono-sized particles at a given time t.

6. Which factor governs the rate of precipitation breakage?

a) Shear rate

b) Particle concentration

c) Shear rate and particle concentration

d) Size of the particle

View Answer

Explanation: The rate of precipitation depends on the shear rate and the particle concentration, when the precipitate particles grow in size and it reaches the size which is enough for the collision among the particles and sticks together, these particles are susceptible to breakage during collision of the particles.

7. Which equation describes the breakage of the protein precipitates?

a) \(\frac{dL}{dt}\) = k(L_{e} + L)^{n}

b) \(\frac{dL}{dt}\) = k(L_{e} – L)^{n}

c) \(\frac{dL}{dt}\) = k(L_{e} × L)^{n}

d) \(\frac{dL}{dt}\) = k(L_{e} ÷ L)^{n}

View Answer

Explanation: The equation \(\frac{dL}{dt}\) = k(L

_{e}– L)

^{n}is a model to describe the breakup of protein precipitates and it is a displacement model to depict the change in the rate of size of aggregates as a function of displacement from the equilibrium diameter. K is the rate constant that depends on the volume fraction of the particle and the shear rate, n = 1 which shows first order reaction.

8. Determine the dependence of population density distribution on the diameter of a particle and its residence time, for the precipitation of protein in a continuous stirred tank reactor.

a) \(\frac{n}{n_0}\) = \((\frac{L_0}{L})^{K_0}\)τ

b) \(\frac{n}{n_0}\) = \((\frac{L_0}{L})^{1/K_0}\)τ

c) \(\frac{n}{n_0}\) = –\((\frac{L_0}{L})^{1+1/K_0}\)τ

d) \(\frac{n}{n_0}\) = \((\frac{L_0}{L})^{1 + \frac{1}{K_0}}\)τ exp[\(\frac{-K_1}{3K_0}\) (L^{3} – \({L_0^3})\)]

View Answer

Explanation: The linear growth rate and particle breakup in population is given by \(\frac{d(K_0 Ln)}{dL} + \frac{n}{\tau}\) + K

_{1}nL

^{3}= 0 after rearrangement the equation becomes, \(\frac{dn}{n}\) = -dL(\(\frac{1 + \frac{1}{K_0 \tau}}{L} + \frac{K_1 L^2}{K_0}\)). With the lower limits of integration of n

_{0}i.e. L = L

_{0}and the critical diameter is L

_{0}, the equation obtained is \(\frac{n}{n_0}\) = \((\frac{L_0}{L})^{1 + \frac{1}{K_0}}\)τ exp[\(\frac{-K_1}{3K_0}\) (L

^{3}– \({L_0^3})\)].

9. When isoelectric precipitation is used as a convenient method for bioseparation?

a) Fractionating a protein mixture

b) Mixing of protein

c) Saturation of protein

d) Dissociation of protein structure

View Answer

Explanation: The Isoelectric precipitation is based on the solubility of the protein and the solubility of the protein is minimum at the isoelectric point of the protein. It is a most convenient method of bioseparation for the fractioning a protein mixture.

10. What is hofmeister series in precipitation process?

a) NH^{+}_{4} < K^{+} < Na^{+}

b) NH^{+}_{4} = K^{+} = Na^{+}

c) NH^{+}_{4} > K^{+} > Na^{+}

d) NH^{+}_{4} < K^{+} > Na^{+}

View Answer

Explanation: Hofmeister series also known as lyotropic series shows the salting out ability of the multiply charged anions and monovalent cations in the order NH

^{+}

_{4}> K

^{+}> Na

^{+}. The salts having multiply charged anions such as sulphate, phosphate and citrate are the effective anions which follow the salting out mechanism and ultimately follow the hofmeister series.

11. What is the assumption of turbulent flow when the impeller speed determines the maximum shear rate?

a) P = 1/\(N_i^3 d_i^5\)

b) P = –\(N_i^3 d_i^5\)

c) P + \(N_i^3 d_i^5\) = 0

d) P = \(N_i^3 d_i^5\)

View Answer

Explanation: The impeller tip speed determines the maximum shear rates and rises when P/V is held constant upon scale-up of the volume of the reactor and these assumes to be turbulent flow, where the power number is constant which shows that P = \(N_i^3 d_i^5\).

12. Calculate the power number for the turbulent flow of particles in the centrifuge tube when the number of impeller is 5 and diameter of the impeller is 5cm.

a) 39 × 10^{3}

b) 39 × 10^{4}

c) 39 × 10^{5}

d) 39 × 10^{6}

View Answer

Explanation: Power number P = \(N_i^3 d_i^5\) = 5

^{3}× 5

^{5}= 39 × 10

^{4}.

13. Calculate the sedimentation velocity of the particle when the centrifuge speed is 2000rpm distance of sample from the centre of rotation to the top of packed solids is 15cm and the distance from the centre of rotation to the top of the liquid in the centrifuge tube is 10cm and the minimum time taken to centrifuge the sample is 150sec.

a) 6.62E – 7 \(\frac{cm}{s}\)

b) 6.62E – 8 \(\frac{cm}{s}\)

c) 6.62E – 9 \(\frac{cm}{s}\)

d) 6.62E – 10 \(\frac{cm}{s}\)

View Answer

Explanation: The sediementation velcoity v

_{g}= \(\frac{g\, ln(\frac{R}{R_o})}{ω^2 t}\) = \(\frac{9.8\, ln(\frac{15}{10})}{2000^2 × 150}\) = \(\frac{3.974}{6 × 10^8}\) = 6.62E – 9 cm/s.

**Sanfoundry Global Education & Learning Series – Bioseparation Processes**.

To practice all areas of Bioseparation Processes, __ here is complete set of 1000+ Multiple Choice Questions and Answers__.