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Interview MCQ Set 1

1. Which of the following separation techniques is dependent on difference in volatility?
a) Distillation
b) Crystallization
c) Magnetic separation
d) Fractional crystallization

View Answer

Answer: a [Reason:] Distillation process is dependent on difference in volatility. Example:- Vapor pressure, Boiling point.

2. Crystallization exploits difference in which factors?
a) Specific heat
b) Boiling point
c) Melting point
d) Bubble point

View Answer

Answer: c [Reason:] The difference in melting point in case of crystallization leads to the separation of the mixture.

3. What is the separation by polymer membrane?
a) Exploits the difference in volatility
b) Exploits the difference in diffusivity
c) Exploits the difference in flowability
d) Exploits the difference in permeability

View Answer

Answer: d [Reason:] In a polymer membrane, only the substances which are suitable to the membrane are passed and the rest do not pass.It can be based on the pore size of the membrane.

4. Which of the following separation techniques exploits differences in electric charge and diffusivity?
a) Chromatography
b) Electrophoresis
c) Distillation
d) Liquid Chromatography

View Answer

Answer: b [Reason:] Electrophoresis is based on the difference in the electrical charges and their diffusivity. Based on the difference in diffusivity of electrical charges, the components are separated.

5. What is the size of equipment determined by?
a) Rate of mass transfer from one phase to another
b) Rate of heat transfer from one phase to another
c) The number of reactions taking place
d) The amount of byproduct formed

View Answer

Answer: a [Reason:] The amount of the feed i.e. the amount of mass transferred from one part of the separation process to another will determine the equipment size. More the mass transfer, larger shall be the equipment.

6. Which of the following is not an important property that governs the extent of separation?
a) Polarizability
b) Vapor pressure
c) Temperature
d) Radius of gyration

View Answer

Answer: c [Reason:] The temperature of the feed will decide the state of the feed and in turn will decide the separation technique to be used. However it will have no effect on extent of separation.

7. Which of the following methods are to be applied to separate Oxygen rich components and Nitrogen rich components?
a) Crystallization
b) Zone melting
c) Magnetic separation
d) Distillation

View Answer

Answer: d [Reason:] The difference between the boiling point of oxygen (-183oC) and Nitrogen (-195.8oC) is frequently large to be separated by distillation.

8. How will you separate o-Xylene and m-Xylene products of the same compounds?
a) Crystallization
b) Distillation
c) Polymer membrane
d) Electrophoresis

View Answer

Answer: a [Reason:] The above mentioned components have same boiling points. So distillation cannot be used. Since they have a difference in melting point, crystallization is used.

9. How is Oil and Hexane separated?
a) Distillation
b) Separating funnel
c) Crystallization
d) Electrophoresis

View Answer

Answer: b [Reason:] Oil and Hexane will have huge differences in the molecular weights. Hence they will form two phases in a separating funnel. Thus the layer that settles down can be removed. Distillation cannot be used here because oil might get damaged.

10. How a mixture of isopropyl alcohol and water is be separated?
a) One step distillation
b) Two step distillation
c) Two step crystallization
d) Separating funnel

View Answer

Answer: b [Reason:] A two-step distillation is employed where there is an addition of benzene which is soluble in IPA and thus forms a layer. Now IPA and benzene mixture can be separated from water using a separating funnel. Further distilling, we get benzene and IPA.

11. How a mixture of iron and copper fillings is be separated?
a) Magnetic separation
b) Crystallization
c) Evaporation
d) Distillation

View Answer

Answer: a [Reason:] Magnetic separation is employed since the components have difference in magnetic properties.

12. How can the DNA fragments be separated from DNA?
a) Crystallization
b) Electrophoresis
c) Distillation
d) Zone melting

View Answer

Answer: b [Reason:] DNA fragments migrate to positive electrode in the electric field.

Interview MCQ Set 2

1. What type of size distribution occurs in batch crystallization?
a) Trimodal
b) Monomodal
c) Bimodal
d) No distribution occurs

View Answer

Answer: c [Reason:] Formation of tiny crystals by a secondary nucleation occurs simultaneously with growth of added seeds. The nuclei formed also grow alongside. This ultimately leads to a bimodal or even multimodal size distribution of the final product.

2. Which of the following is not a common method in reducing the rate of nucleation?
a) To control supersaturation
b) To keep low level of turbulence of mixing
c) To keep the slurry density low
d) To keep high level of turbulence of mixing

View Answer

Answer: b [Reason:] A narrow crystal size distribution can be achieved if there is little or no nucleation, so that the final product is the result of growth of the seeds only. The common methods of reducing the rate of nucleation (a) to control the supersaturation level, (b) to keep a low level of turbulence or mixing, (c) to keep the slurry density low.

3. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 400 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.06lit/min
c) 0.07lit/min
d) 0.08lit/min

View Answer

Answer: a [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.05lit/min.

4. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 800 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.06lit/min
c) 0.07lit/min
d) 0.1lit/min

View Answer

Answer: d [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.1lit/min.

5. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 600 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.0625lit/min
c) 0.07lit/min
d) 0.08lit/min

View Answer

Answer: a [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.0625lit/min.

6. Find the initial rate of evaporation if
Mass of seed=Ms= 0.924 kg,
Solubility C = 400 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.10lit/min
c) 0.15lit/min
d) 0.08lit/min

View Answer

Answer: c [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.15lit/min.

7. Find the initial rate of evaporation if
Mass of seed=Ms= 3.08 kg,
Solubility C = 400 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.5lit/min
c) 0.7lit/min
d) 0.8lit/min

View Answer

Answer: b [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.5lit/min.

8. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 200 kg/m3, G/Ls= 3.75 x 10-4
a) 0.0225lit/min
b) 0.06566lit/min
c) 0.0527lit/min
d) 0.5408lit/min

View Answer

Answer: a [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.0225lit/min.

9. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 80 kg/m3, G/Ls= 3.75 x 10-4
a) 0.01lit/min
b) 0.02lit/min
c) 0.03lit/min
d) 0.04lit/min

View Answer

Answer: a [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.01lit/min.

10. Find the initial rate of evaporation if
Mass of seed=Ms= 0.308 kg,
Solubility C = 1600 kg/m3, G/Ls= 3.75 x 10-4
a) 0.05lit/min
b) 0.15lit/min
c) 0.20lit/min
d) 0.25lit/min

View Answer

Answer: c [Reason:] Since -dV/dt=3MsGc/Ls for initial rate of evaporaton, initial rate=0.20lit/min.

Interview MCQ Set 3

1. What is the definition of azeotropic mixture?
a) A liquid mixture of two or more substances that boils at a constant characteristic temperature lower or higher than anyof its components and that retains the same composition in the vapor state as in the liquid state.
b) A liquid mixture of two or more substances that boils at a different characteristic temperature
c) A liquid mixture of two or more substances that boils at a constant characteristic pressure
d) A liquid mixture of two or more substances that boils at a constant characteristic temperature and pressure

View Answer

Answer: a [Reason:] A liquid mixture of two or more substances that boils at a constant characteristic temperature lower or higher than anyof its components and that retains the same composition in the vapor state as in the liquid state.

2. What is the value of K for azeotropic mixtures?
a) 0
b) 1
c) 2
d) 3

View Answer

Answer: b [Reason:] The vapor and liquid compositions are identical for azeotropic mixture; hence the K value is 1.

3. Isopropyl ether-isopropyl alcohol is which type of azeotropic mixture?
a) Minimum boiling heterogeneous mixture
b) Maximum boiling heterogeneous mixture
c) Minimum boiling homogeneous mixture
d) Minimum boiling heterogeneous mixture

View Answer

Answer: c [Reason:] Isopropyl ether-isopropyl alcohol is minimum boiling homogeneous mixture.

4. Which of the following is true?
a) Heterogeneous mixtures are minimum boiling point mixture
b) Homogeneous mixtures are minimum boiling point mixture
c) Heterogeneous mixtures are maximum boiling point mixture
d) Homogeneous mixtures are maximum boiling point mixture

View Answer

Answer: a [Reason:] Heterogeneous mixtures are minimum boiling point mixtures because activity coefficients should be significantly greater than 1.

5. Which of the following is not true?
a) If more than one liquid phase exists,it is heterogenous azeotrope
b) A vapor can coexist with no more than two liquid phases
c) If the solution is layered then it is heterogeneous azeotrope
d) If one liquid phase exists it’s a homogeneous azeotrope

View Answer

Answer: c [Reason:] If the solution is layered then it is heterogeneous azeotrope is wrong and all other options are correct.

6. Which of the following is most common azeotrope?
a) Minimum boiling heterogeneous
b) Maximum boiling heterogeneous
c) Maximum boiling homogeneous
d) Minimum boiling homogeneous

View Answer

Answer: d [Reason:] Minimum boiling homogeneous azeotropes are most common. E.g.:- isopropyl ether-isopropyl alcohol.

7. What happens when activity coefficients are greater than 1?
a) The maximum total pressure is smaller than vapor pressure of either component
b) The maximum total pressure is greater than vapor pressure of either components
c) The maximum total pressure is greater than one component only
d) The minimum total pressure is greater than vapor pressure of either components

View Answer

Answer: The maximum total pressure is greater than vapor pressure of either component when the activity coefficients are greater than 1.

8. Where are maximum boiling homogeneous azeotropes approached in distillation?
a) Bottom product
b) Top product
c) Vapors
d) Separate channel required

View Answer

Answer: a [Reason:] The maximum boiling homogeneous azeotropes approached in distillation at the bottom product.

9. How is it possible to shift the equilibrium to advantage in azeotropic mixture?
a) Changing the volume
b) Adding more mixture
c) Adding one of the component more
d) Changing the pressure.

View Answer

Answer: d [Reason:] By changing the pressure it is possible to shift the equilibrium and “break” the azeotrope.

10. Which of the following could be an azeotropic mixture?
a) Components belonging to same functional group
b) Geometrical isomers
c) Functional isomers
d) Chain isomers

View Answer

Answer: c [Reason:] The functional isomers could have nearly same boiling points hence they could form an azeotropic mixture.

Interview MCQ Set 4

1. Which of the following is the correct formula for gibb’s phase rule?
a) F=c+p
b) F=c+p-2
c) F=c-p-2
d) F=c*p -2

View Answer

Answer: b [Reason:] The correct formula for gibb’s phase rule is F=c+p-2.

2. What are the degrees of freedom if there are two components in two phases?
a) 0
b) 2
c) 4
d) 6

View Answer

Answer: b [Reason:] Since F=c+p-2, when c=2 and p=2, F= 2+2-2=2.

3. Which of the following is not true?
a) yB= 1- yA
b) xB = 1-xA
c) yA= 1- yB
d) xB= 1- yB

View Answer

Answer: d [Reason:] xB= 1- yB is incorrect since xb+yb is not equal to 1.

4. Which of the following techniques is not used when the boiling point difference is too small?
a) Crystallization
b) Adsorption
c) Distillation
d) Zone melting

View Answer

Answer: c [Reason:] Distillation is impractical when the boiling point difference is too small since large amount of trays are required for obtaining pure products.

5. Which of the following is correct definition of bubble point?
a) Boiling point
b) Temperature at which bubbles start
c) Temperature at which pressure of bubbles is highest
d) Temperature at which first bubble comes

View Answer

Answer: d [Reason:] The temperature at which the first bubble is seen is called the bubble point.

6. What is the definition of critical point?
a) The temperature or pressure beyond which the liquid-vapor cannot co-exist
b) The temperature or pressure beyond which the liquid-liquid mixture cannot co-exist
c) The temperature or pressure beyond which the vapor vanishes
d) The temperature or pressure beyond which the bubbles start coming

View Answer

Answer: a [Reason:] The temperature or pressure beyond which the liquid-vapor cannot co-exist and yA=xA.

7. What is the correct definition of dew point?
a) The point at which first drop of gas boils
b) The point at which the first drop of liquid boils
c) The point at which the first drop of gas condenses
d) The point at which the bubble comes

View Answer

Answer: c [Reason:] Dew point is the point at which the first drop of gas condenses.

8. When does the relative volatility vary little with pressure?
a) For broad boiling point mixture showing non-ideal behavior
b) For narrow boiling point mixtures showing non-ideal behavior
c) For narrow boiling point mixtures showing ideal behavior
d) For broad boiling point mixtures showing idal behavior

View Answer

Answer: c [Reason:] The relative volatility varies little with pressure for narrow boiling point mixtures showing ideal behavior.

9. From the knowledge of vapor pressures of components, a y=x equilibrium can be approximated using how many values of αA,B?
a) Zero
b) One
c) Two
d) Three

View Answer

Answer: b [Reason:] From the knowledge of vapor pressures of components, a y=x equilibrium can be approximated using only one value of αA,B.

10. Which of the following is untrue about Roult’s law?
a) P=PAsxA + PBsxB
b) P=PAsxA + PBs(1-xA)
c) P= PAsxA + PAs(1-xA)
d) P=PsB + xA(PsA-PsB)

View Answer

Answer: c [Reason:] All other forms are correct except P= PAsxA + PAs(1-xA).

Interview MCQ Set 5

1. What does the Attrition mean?
a) Coalescence of molecules
b) Collision of solid crystals with each other
c) Breakup of existing crystals in new particles
d) Mechanism that gives different crystal size distributions

View Answer

Answer: c [Reason:] The term attrition refers to breakup of existing crystals in new particles.

2. What does the term contact nucleation?
a) Coalescence of molecules
b) Collision of solid crystals with each other
c) Breakup of existing crystals in new particles
d) Mechanism that gives different crystal size distributions

View Answer

Answer: b [Reason:] The term contact nucleation refers to collision of solid crystals with one another.

3. What does the term chronomals refer to?
a) Coalescence of molecules
b) Collision of solid crystals with each other
c) Breakup of existing crystals in new particles
d) Mechanism that gives different crystal size distributions

View Answer

Answer: d [Reason:] Chronomals refer to the mechanism that gives different crystal size distribution.

4. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 5g/m3
Area of crystal A= 10m2
a) 1.2m
b) 1.4
c) 1m
d) 2m

View Answer

Answer: a [Reason:] Since L= 6m/dA, L= 1.2m.

5. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 6g/m3
Area of crystal A= 10m2
a) 1.2m
b) 1.4
c) 1m
d) 2m

View Answer

Answer: c [Reason:] Since L= 6m/dA, L= 1m.

6. Find out the characteristic crystal length if
Mass of the crystal m= 16.67g
Density of crystal is d= 5g/m3
Area of crystal A= 10m2
a) 1.2m
b) 1.4
c) 1m
d) 2m

View Answer

Answer: d [Reason:] Since L= 6m/dA, L= 2m.

7. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 2g/m3
Area of crystal A= 10m2
a) 1.2m
b) 3m
c) 1m
d) 2m

View Answer

Answer: b [Reason:] Since L= 6m/dA, L= 3m.

8. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 1g/m3
Area of crystal A= 10m2
a) 1.2m
b) 1.4
c) 1m
d) 6m

View Answer

Answer: d [Reason:] Since L= 6m/dA, L= 6m.

9. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 4g/m3
Area of crystal A= 10m2
a) 1.2m
b) 1.5m
c) 1m
d) 2m

View Answer

Answer: b [Reason:] Since L= 6m/dA, L= 1.5m.

10. Find out the characteristic crystal length if
Mass of the crystal m= 10g
Density of crystal is d= 9g/m3
Area of crystal A= 10m2
a) 0.33m
b) 0.66m
c) 0.69m
d) 0.56m

View Answer

Answer: b [Reason:] Since L= 6m/dA, L= 0.66m.