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Interview MCQ Set 1

1. Which of the following is not an indirect heat batch dryer?
a) Jacketed-shelf dryer
b) Agitated pan dryer
c) Conical vacuum dryer
d) Drum dryer

View Answer

Answer: d [Reason:] Drum dryer is a continuous type of dryer.

2. Which of the following is not a continuous heat dryer?
a) Indirect hear rotary dryer
b) Drum dryer
c) Freeze dryer
d) Conical vacuum dryer

View Answer

Answer: d [Reason:] Conical vacuum dryer is a type of batch dryer.

3. The type of agitator and the RPM depend on what in agitated pan dryer?
a) Surrounding conditions
b) Surrounding temperature
c) Material to be dried
d) Volume of material desired

View Answer

Answer: c [Reason:] The RPM depend on the material to be dried.

4. What is the vacuum dryer suitable for?
a) Heat sensitive materials
b) High molecular weight material
c) Low molecular weight materials
d) Highly viscous materials

View Answer

Answer: a [Reason:] Since the operation is carried out in vacuum it is suitable for heat sensitive materials.

5. What is the use of the conical shape in the conical vacuum dryer?
a) It allows high area to be exposed for drying
b) Allows faster discharge of material through bottom
c) It doesn’t allow the material to stick
d) It helps slow transfer if material

View Answer

Answer: b [Reason:] The conical shape of vacuum dryer allows faster discharge of product through bottom.

6. What is the efficiency of Indirect heat rotary dryer?
a) 70%
b) 80%
c) 95%
d) 100%

View Answer

Answer: c [Reason:] The loss of heat through the heating gas is much less and indirect heat dryer has efficiency of 95%.

7. What is drum dryer suitable for?
a) Materials which are too thin for rotary dryer and too thick for spray dryer
b) Materials which are too thin for spray dryer and too thick for rotary dryer
c) Very thin materials
d) Very thick slurries

View Answer

Answer: a [Reason:] Drum dryer is suitable for materials which are too thin for rotary dryer and too thick for spray dryer.

8. Which dryer is used for drying food products?
a) Drum dryer
b) Freeze dryer
c) Rotary dryer
d) Agitated pan dryer

View Answer

Answer: b [Reason:] Freeze dryer is used for drying food products.

9. What is screw dryer suitable for?
a) Very thick slurries
b) Materials which are heat sensitive
c) Free flowing granular materials
d) Free flowing slurries

View Answer

Answer: c [Reason:] Screw dryer is suitable for free flowing granular materials.

10. At what temperature is the vapor condensed is freeze dryer?
a) -20oc
b) -30oc
c) -40oc
d) -60oc

View Answer

Answer: d [Reason:] The vapor is condensed to about -60 degree in freeze dryer.

Interview MCQ Set 2

1. What are cascades?
a) They are the one step separation processes
b) They are the last part of separation processes
c) They are an aggregation of stages
d) They are the starting part of every separation process

View Answer

Answer: c [Reason:] Cascades are the aggregates of stages needed to accomplish separation that cannot be attained in one step.

2. What is NOT the need of cascades?
a) To accomplish separation that cannot be attained in one step
b) To increase the purity of products
c) To reduce the amount of mass or energy separating agents required
d) To make the efficient use of raw materials

View Answer

Answer: b [Reason:] Cascades can promise efficiency but not purity.

3. Countercurrent cascades are not prevalent in which process?
a) Crystallization
b) Distillation
c) Stripping
d) Liquid-liquid extraction

View Answer

Answer: a [Reason:] Cascades are not required in crystallization.

4. What is used when the extent of separation is limited by a single step separation?
a) Distillation and pervaporation
b) Cascades
c) Multistage process
d) Hybrid systems

View Answer

Answer: d [Reason:] When the extent of separation is limited by a single step separation hybrid systems are used.

5. Which is a widely used cascade?
a) Cross-current cascade
b) Linear Counter current cascade
c) Linear concurrent cascade
d) Single section cascade

View Answer

Answer: b [Reason:] Linear Counter current cascade are most widely used.

6. Batch crystallization uses which type of cascades?
a) Cross-current cascade
b) Linear Counter current cascade
c) Linear concurrent cascade
d) Two dimensional diamond configuration

View Answer

Answer: d [Reason:] Batch crystallization uses two dimensional diamond configurations.

7. Which cascades are not useful in separating key components?
a) Single section cascades
b) Two section countercurrent cascades
c) Interlinked system of countercurrent cascades
d) Three section cascades

View Answer

Answer: a [Reason:] Single section cascades are useful to remove the feed but not to separate the keycomponents.

8. Which cascade is used in fractional liquid-liquid extraction?
a) Two section countercurrent cascade
b) Cross current cascade
c) Two-dimensional diamond configuration
d) Interlinked system of countercurrent cascades

View Answer

Answer: a [Reason:] Two section countercurrent cascades are used in fractional liquid-liquid extraction.

9. Leaching uses which cascade configuration?
a) Single section countercurrent
b) Cross current cascade
c) Two dimensional diamond configuration
d) Interlinked system of countercurrent cascades

View Answer

Answer: a [Reason:] A single section countercurrent cascade is used in leaching or washing process.

10. Which cascade does not consist of single section?
a) Single section countercurrent cascades
b) Crosscurrent cascades
c) Interlinked system of countercurrent cascades
d) Two dimensional diamond configuration

View Answer

Answer: c [Reason:] Interlinked system of countercurrent cascades is a two section process.

Interview MCQ Set 3

1. What are the two general types of centrifuge devices for solid-liquid separations?
a) Sedimentation centrifuges, filtering centrifuges
b) Sedimentation centrifuges, decantation centrifuges
c) Filtering centrifuges, sintering centrifuges
d) Sedimentation centrifuges, two way centrifuges

View Answer

Answer: a [Reason:] The two general types of centrifuge devices for solid-liquid separations are Sedimentation centrifuges, filtering centrifuges.

2. What is the use of tubular-bowl centrifuge?
a) To separate soap from oil
b) To separate waste material
c) To separate cells and viruses from broth
d) To separate salts from mixtures

View Answer

Answer: c [Reason:] The tubular-bowl centrifuge is used to separate cells and viruses from broth.

3. In which industry tubular-bowl centrifuge not used?
a) Food industry
b) Pharma industry
c) Biochemical industry
d) Metallurgical industry

View Answer

Answer: d [Reason:] The tubular-bowl centrifuge is used to separate cells and viruses from broth and hence has no use in the metal industry.

4. When is the basket-filtering centrifuge not used?
a) Solids are main product
b) Low cake moisture content
c) High solid recovery desired
d) High liquid recovery desired

View Answer

Answer: d [Reason:] When high liquid recovery is desired, basket filtering centrifuge is not used.

5. Why are gravity separators not used in bioseparations?
a) Because density differences are very large
b) Because density differences are very small
c) Because gravity separators are too small
d) Because the cultures get damaged

View Answer

Answer: b [Reason:] Gravity separators are not used in bioseparations because density differences are very small.

6. Calculate the sigma factor for the following operating conditions
Bowl length L=0.1m
Rotation rate n=2000/s
R0=0.02m, R1=0.01m
a) 50
b) 55
c) 111
d) 165

View Answer

Answer: b [Reason:] Sigma factor= Lω2(R02-R12)/gln(R0/R1), hence sigma factor= 55m.

7. Calculate the sigma factor for the following operating conditions
Bowl length L=0.2m
Rotation rate n=2000/s
R0=0.02m, R1=0.01m
a) 50
b) 55
c) 111
d) 165

View Answer

Answer: c [Reason:] Sigma factor= Lω2(R02-R12)/gln(R0/R1), hence sigma factor= 111m.

8. Calculate the sigma factor for the following operating conditions
Bowl length L=0.3m
Rotation rate n=2000/s
R0=0.02m, R1=0.01m
a) 50
b) 55
c) 111
d) 165

View Answer

Answer: d [Reason:] Sigma factor= Lω2(R02-R12)/gln(R0/R1), hence sigma factor= 111m.

9. Calculate the sigma factor for the following operating conditions
Bowl length L=0.05m
Rotation rate n=2000/s
R0=0.02m, R1=0.01m
a) 27
b) 55
c) 111
d) 165

View Answer

Answer: a [Reason:] Sigma factor= Lω2(R02-R12)/gln(R0/R1), hence sigma factor= 27m.

10. Calculate the sigma factor for the following operating conditions
Bowl length L=0.1m
Rotation rate n=4000/s
R0=0.02m, R1=0.01m
a) 323
b) 212
c) 234
d) 222

View Answer

Answer: d [Reason:] Sigma factor= Lω2(R02-R12)/gln(R0/R1), hence sigma factor= 222m.

Interview MCQ Set 4

1. Which dryer is also called as pneumatic conveyer?
a) Flash dryer
b) Fluidized bed dryer
c) Spray dryer
d) Drum dryer

View Answer

Answer: a [Reason:] Flash dryer is also called as pneumatic conveyer essentially contains a vertical conveyer pipe.

2. Which of the following is not an air suspended drying system?
a) Rotary dryer
b) Flash dryer
c) Spray dryer
d) Fluidized bed dryer

View Answer

Answer: a [Reason:] Rotary dryer is a continuous dryer but is not air suspended.

3. Which of the following materials is suitable for flash dryer?
a) Heat sensitive materials
b) Heat stable materials
c) Highly viscous materials
d) Granular slurries

View Answer

Answer: a [Reason:] Flash dryer is used to dry heat sensitive like proteins.

4. What is the flash dryer unsuitable for?
a) Heat sensitive materials
b) Heat stable materials
c) Highly viscous materials
d) Large or heavy particles

View Answer

Answer: d [Reason:] The flash dryer is suitable for large or heavy particles.

5. Which materials cannot be dried in fluidized bed dryer?
a) Meat
b) Fish
c) Spices
d) Proteins

View Answer

Answer: d [Reason:] Since proteins are thermo labile the cannot be dried in fluidized bed dryer.

6. Which dryer is used to dry atomized droplets of a feed?
a) Spray dryer
b) Flash dryer
c) Drum dryer
d) Fluidized bed dryer

View Answer

Answer: a [Reason:] Spray dryer is sued to dry atomized droplets of feed.

7. What is the contact time in a spray dryer?
a) Few minutes
b) Few hours
c) Few seconds
d) No direct contact

View Answer

Answer: c [Reason:] The contact time is of few second.

8. What can be the maximum temperature of hot gas in a spray dryer(oc)?
a) 300
b) 400
c) 100
d) 700

View Answer

Answer: d [Reason:] The maximum temperature if hot gas can be as high as 700oc but it is normally 200-300oc.

9. Due to short contact time in spray dryer what is it used to dry?
a) Thermo labile materials
b) Highly viscous materials
c) Heavy materials
d) Not used at all

View Answer

Answer: a [Reason:] Due to short contact time spray dryer is used to dry thermo labile materials.

10. What is the wavelength used in microwave dryer?
a) UV
b) Visible
c) Radio waves
d) Microwaves

View Answer

Answer: c [Reason:] To heat the material the wavelength used is as long as radio waves.

Interview MCQ Set 5

1. What is the crystal size range of forced circulation crystallizer?
a) 10-20mesh
b) 20-30mesh
c) 30-60mesh
d) 100-200mesh

View Answer

Answer: c [Reason:] In the forced circulation crystallizer a crystal of size of 30-60mesh are mesh are produced.

2. Why the axial pump flow speed is preferred in forced circulation crystallizer?
a) To reduce primary nucleation rate
b) To reduce the crystal size
c) To increase the crystal size
d) To keep the secondary nucleation rate small

View Answer

Answer: d [Reason:] An axial flow pump is preferred, the pump speed should be low in order to reduce the energy input so that the secondary nucleation by contact or attrition remains small.

3. What is the crystal size range of draft-tube-baffle crystallizer?
a) 1-2 mesh
b) 30-60mesh
c) 8-30mesh
d) 100-200mesh

View Answer

Answer: c

Explanation: The crystal size range of draft-tube-baffle crystallizer is 8-30mesh.

4. What is the near ambient temperature range for most inorganic solids?
a) 10-20
b) 10-40
c) 40-67
d) 70-80

View Answer

Answer: b [Reason:] The near ambient temperature range for most inorganic solids is 10-40 degrees.

5. Which type of crystallizers does industry employ?
a) Evaporative
b) Cooling
c) Sublimating
d) Boiling

View Answer

Answer: a [Reason:] Mostly, evaporative crystallizers or a combination of evaporative and cooling crystallizers is used.

6. What is not an advantage of using mechanical agitation?
a) High purity
b) Uniform crystal size
c) High purity
d) Low rate of primary nucleation

View Answer

Answer: d [Reason:] A high rate of primary nucleation is required so it cannot be an advantage.

7. What is the result of unagitated batch crystallizers?
a) Undesirably large crystals
b) Impure crystals
c) Entrapment of mother liquor
d) High secondary nucleation rate

View Answer

Answer: d [Reason:] High secondary nucleation rate is the result of high speed of the agitator.

8. What ensures a reasonable heat transfer rate through a small temperature driving force?
a) High agitation speed
b) High magma velocity
c) High nucleation rate
d) Low nucleation rate

View Answer

Answer: b [Reason:] A high magma velocity ensures a small temperature driving force.

9. What is the time for a typical cycle, including charging the feed, crystallization, and removal of the magma?
a) 1 hour
b) 2-8hr
c) 7-15hr
d) 5-14hr

View Answer

Answer: b [Reason:] 2-8hr is the time for a typical cycle, including charging the feed, crystallization, and removal of the magma.

10. What is the specialty of the circulating liquor crystallizer?
a) Supersaturaion is created in separate region
b) Supersaturation is not created
c) Supersaturation is created at every point
d) Crystals are automatically thrown out of crystallizer

View Answer

Answer: a [Reason:] The speciality of circulating liquor crystallizer equipment is that supersaturation is created in a separate region before the liquor flows into the crystal suspension vessel. The “level” of supersaturation drops down as the liquor from the supersaturated zone mixes up with the slurry.