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Interview MCQ Set 1

1. What is the role of Energy-separating agent (ESA)?
a) Involves heat transfer
b) Involves mass transfer
c) Acts as an agitator
d) Is a catalyst

View Answer

Answer: a [Reason:] The role of ESA is to perform heat transfer. Example: Creation of vapor from liquid phase by reducing pressure.

2. Which of the following is NOT a disadvantages of using a mass-separating agent (MSA) ?
a) Need for additional separator to remove MSA
b) Possible MSA contamination
c) Difficult design procedures
d) Need for large quantities of MSA

View Answer

Answer: d [Reason:] There is no need for large quantities of MSA and the quantities are defined by the amount of feed.

3. Which separation process is used when the volatility differences is too small between the species?
a) Flash vaporization
b) Stripping
c) Extractive distillation
d) Liquid-Liquid extraction

View Answer

Answer: c [Reason:] Extractive distillation is used where a miscible MSA increases the volatility difference between the components.

4. What is added when it is difficult to condense vapors leaving the distillation column at top?
a) Adsorbent
b) Absorbent
c) Agitator
d) ESA

View Answer

Answer: b [Reason:] The absorbent help to condense the vapor leaving the distillation column.

5. Which separation technique shall be used to remove ethane and lower molecular weight hydrocarbons for LPG production?
a) Flash vaporization
b) Distillation
c) Reboiled absorption
d) Stripping

View Answer

Answer: c [Reason:] Reboiled absorption shall be used since it is difficult to condense the ethane vapors leaving from the top.

6. Which separation technique shall be employed to separate acetone and methanol?
a) Extractive distillation
b) Stripping
c) Liquid-Liquid extraction
d) Evaporation

View Answer

Answer: a [Reason:] Extractive distillation shall be used here since the volatility difference is very small.

7. In azeotropic distillation, why is an entrainer added?
a) To increase the boiling point of the mixture
b) To decrease the boiling point of the mixture
c) To form a minimum boiling point azeotrope
d) To form two immiscible phases

View Answer

Answer: c [Reason:] In the separation of acetic acid with water, -butyl acetate is added which acts as an entrainer and forms two liquid, minimum boiling point azeotrope with water. It is then overhead and condensed and separated in acetate and water layers.

8. When is the liquid-liquid extraction preferred over distillation?
a) When the distillation apparatus is not available
b) Distillation apparatus is costly
c) When there too very high difference in the boiling points.
d) When the liquid mixture is temperature sensitive

View Answer

Answer: d [Reason:] When the liquid mixture is temperature sensitive, liquid-liquid extraction is used by adding a solvent that selectively dissolves in one of the liquids.

9. Which of the following solvents can be added during separation of Isopropyl alcohol and water?
a) Methanol
b) Ethanol
c) Benzene
d) Alcoholic KOH

View Answer

Answer: c [Reason:] Benzene selectively dissolves in IPA and thus two layers are formed which can be separated using a separating funnel.

10. How is sulphur separated from its impurities?
a) Desublimation
b) Sublimation
c) Crystallization
d) Drying

View Answer

Answer: b [Reason:] Sublimation is the technique used since sulphur can be sublimed and then condensed.

11. Where is the technique of leaching used?
a) Research laboratories
b) Soap industry
c) Pharmaceutical industry
d) Metallurgical industry

View Answer

Answer: d [Reason:] Leaching is used in extraction of metals in metallurgical industry.

Interview MCQ Set 2

1. What is a nomograph?
a) A graph containing relationship between two quantities
b) A graph containing relationship between three quantities
c) A graph containing relationship between three or more quantities
d) A graph containing diagrams

View Answer

Answer: c [Reason:] A nomograph is a a diagram representing the relations between three or more variable quantities by means of a number of scales, so arranged that the value of one variable can be found by a simple geometrical construction, e.g. by drawing a straight line intersecting the other scales at the appropriate values.

2. The convergence pressure depends on what?
a) Densities of the components
b) Amounts of the components
c) Melting points of the components
d) Boiling points of the components

View Answer

Answer: d [Reason:] The convergence pressure from the nomograph depends on the boiling points of the components when the K values collapse to 1.0.

3. What is the convergence pressure for narrow boiling point mixtures?
a) less than 5000psia
b) less than 2500psia
c) less than 1000psia
d) less than 500psia

View Answer

Answer: c [Reason:] For narrow boiling point range like ethane and propoane the convergence pressure is less than 1000psia.

4. Why are there no charts available for liquid-liquid distribution?
a) The values are different every time
b) Because of pronounced effect of composition
c) Because the distribution is tough to find
d) There is no convergence pressure

View Answer

Answer: b [Reason:] No simple charts are available for estimating liquid-liquid distribution because of pronounced effect of composition.

5. What estimation is available for dilute solutions that are ternary and contain almost immiscible solvents?
a) A tabular distribution of partition coefficients by robins
b) A tabular distribution of partition coefficients by keller
c) A tabular distribution of partition coefficients by Haden
d) A tabular distribution of partition coefficients by Grayson

View Answer

Answer: a [Reason:] For estimation is available for dilute solutions that are ternary and contain almost immiscible solvents a tabular distribution of partition coefficients by robins is used.

6. What Is NOT the use of plots of thermodynamic properties?
a) Used to establish correlations.
b) Used to make general observation
c) Used to extrapolate and find unknown quantities
d) Used to know the purity

View Answer

Answer: d [Reason:] Plots of thermodynamic properties don’t tell us about the purity of components.

7. Which equation is fitted in the plot of vapor pressure versus temperature?
a) Roult’s law
b) Newton’s law
c) Antoine Equation
d) Gibb’s equation

View Answer

Answer: c [Reason:] The plots are supposed to fit and follow the Antoine equation.

8. How are Nomographs used?
a) They give the direct reading
b) By joining the lines and extrapolating
c) By finding out points, joining the lines and extrapolating
d) Nomographs are ancient and thus not used

View Answer

Answer: c [Reason:] Nomographs are used by finding out points, joining the lines and extrapolating to the desired quantity wanted.

9. If the partial vapor pressure of the component is 1000pa in the gaseous mixture and the vapor pressure of pure component is 2000pa what is the mole fraction of the solute?
a) 2
b) 1
c) 1.5
d) 0.5

View Answer

Answer: d [Reason:] Psi/P. Hence xi = 1000/2000=0.5.

10. What is the K-value if the partial vapor pressure of the component is 360Pa in gaseous mixture and the vapor pressure of pure component is 500Pa.
a) 0.43
b) 0.55
c) 0.72
d) 0.88

View Answer

Answer: c [Reason:] Ki = Psi/P .Hence K=260/500=0.72.

Interview MCQ Set 3

1. Which of the following is an advantage of using the continuous countercurrent operation?
a) Maximizes the average driving force for transport
b) Maximizes the efficiency
c) Maximizes the cost
d) Minimizes the cost

View Answer

Answer: a [Reason:] Countercurrent flow maximizes the average driving force for transport → increases adsorbent use efficiency.

2. What relationship is true about solute free mass flow rates?
a) F/S less than K less than D/S
b) D/S less than K less than F/S
c) F/S less than D/S less than K
d) D/S less than F/S less than K

View Answer

Answer: a [Reason:] F/S less than K less than D/S is true for solute free mass flow rates.

3. What is untrue for Mcabe thiele method for adsorption at elevated temperatures?
a) F/S cannot be greater than D/S
b) The two operating lines must intersect at the point (qR , cR )
c) Desorption line is placed below adsorption line by elevating temperature
d) Elevated pressure can also be used

View Answer

Answer: a [Reason:] F/S can be greater than D/S for Mcabe thiele method for adsorption at elevated temperatures.

4. If KA= 20, KB=30, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.4
b) 0-0.81
c) 0.81-1
d) 0.9-1

View Answer

Answer: c [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 20/30=0.81.

5. If KA= 40, KB=50, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.4
b) 0-0.81
c) 0.81-1
d) 0.89-1

View Answer

Answer: d [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 40/50=0.89.

6. If KA= 20, KB=80, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.4
b) 1-0.5
c) 0.81-1
d) 0.9-1

View Answer

Answer: b [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 20/80=0.5.

7. If KA= 36, KB=100, what is the permissible values ,what is the safety margin for TMB model is:
a) 1-0.6
b) 0-0.81
c) 0.66-1
d) 0.36-1

View Answer

Answer: a [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 36/100=0.6.

8. If KA= 50, KB=60, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.4
b) 1-0.89
c) 0.91-1
d) 0.97-1

View Answer

Answer: c [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 50/60=0.91.

9. If KA= 40, KB=80, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.5
b) 1-0.5
c) 0.70-1
d) 0.5-1

View Answer

Answer: c [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 40/80=0.70.

10. If KA= 10, KB=60, what is the permissible values ,what is the safety margin for TMB model is:
a) 0-0.40
b) 1-0.167
c) 0.45-1
d) 0.407-1

View Answer

Answer: d [Reason:] Since the permissible range is between 1 and square root of Ka/Kb, the limit is square root of 10/60=0.40z.

Interview MCQ Set 4

1. What does N stand for?
a) Number of processes
b) Number of stages
c) Number of equipment
d) Ratio of feed to product

View Answer

Answer: b [Reason:] N stands for the number of stages corresponding to a cascade.

2. When does the graphical method become tedious?
a) When there are too many solvents
b) When too many stages are involved
c) When more than one solute is adsorbed or stripped
d) When the solute to be stripped is unknown

View Answer

Answer: c [Reason:] The graphical method becomes tedious when more than one solute is adsorbed or stripped.

3. Which method is applied when graphical method is unsuitable?
a) Keller method
b) Newton’s method
c) Distillation method
d) Kremser method

View Answer

Answer: d [Reason:] Kremser method is applied when graphical method is unsuitable.

4. What is the formula for fraction of the solute i absorbed?
a) A i N+1 – 1/ A i N+1 –A i
b) A i N+1 – A i / A i N+1 –1
c) S i N+1 – S i / S i N+1 –1
d) S i N+1 – A i / S i N+1 –1

View Answer

Answer: b [Reason:] The formula for fraction of the solute I absorbed is A i N+1 – A i / A i N+1 –1 where A i = L/K i V.

5. What is the formula for fraction of the solute i stripped?
a) A i N+1 – 1/ A i N+1 –A i
b) A i N+1 – A i / A i N+1 –1
c) S i N+1 – S i / S i N+1 –1
d) S i N+1 – A i / S i N+1 –1

View Answer

Answer: c [Reason:] The formula for fraction of the solute I stripped is S i N+1 – S i / S i N+1 –1 Where S i = K i V/L.

6. Which of the following does not give a correct expression for K i ?
a) Roult’s law
b) Henry’s law
c) Modified Roult’s law
d) Gas law

View Answer

Answer: d [Reason:] The gas law is PV=nRT and it does not give an expression for K i .

7. When is the Roult’s law used?
a) Ideal solutions involving solutes at sub-critical temperatures
b) Non-ideal solutions involving solvents at sub-critical temperatures
c) Ideal solution involving solutes at critical temperatures
d) Non-ideal solutions involving solutes at critical temperatures

View Answer

Answer: a [Reason:] The roullt’s law where K i = P s i /P is applied for Ideal solutions involving solutes at sub-critical temperatures.

8. Which equation is used for solutes at supercritical temperatures?
a) Roult’s law
b) Henry’s law
c) Modified Roult’s law
d) Gas law

View Answer

Answer: b [Reason:] The henry’s law which is K i =H i /P is used for solutes at supercritical temperatures.

9. Which equation is sued for sparingly soluble solutes at sub-critical temperatures?
a) Roult’s law
b) Henry’s law
c) Modified Roult’s law
d) Solubility equation

View Answer

Answer: d [Reason:] The solubility equation K i = P s i /x * i P is used for sparingly soluble solutes at sub-critical temperatures.

10. What is the formula for solute absorption factor?
a) Ai = LV/Ki
b) Si = Ki V/L
c) Ai =L/Ki V
d) Si = Ki /LV

View Answer

Answer: c [Reason:] Ai =L/Ki V is the formula for solute absorption factor where L and V are the feed rates.

Interview MCQ Set 5

1. In crystallization, solvent should dissolve large amount of solute at:
a) Room temperature
b) Boiling point
c) Freezing point
d) Slip melting point

View Answer

Answer: b [Reason:] Solvent should dissolve large amount of solute at boiling point of solvent.

2. Insoluble impurities during crystallization are removed by:
a) Decantation
b) Filtration
c) Distillation
d) Fractional crystallization

View Answer

Answer: b [Reason:] Since the impurities are insoluble they can be easily removed by filtration and no other methods are required.

3. The crystals obtained in crystallization are dried by:
a) Dryer
b) Oven
c) Filter paper
d) Exposing to sun

View Answer

Answer: c [Reason:] The moisture is sucked with the help of a filter paper and the crystals are dried.

4. Which of the following is not an assumption of MSMPR model?
a) Perfect mixing of the magma
b) No crystal breakage
c) Continuous, steady-flow, steady-state operation
d) Crystals are of various sizes.

View Answer

Answer: d [Reason:] The crystals are assumed to be of same size in the MSMPR model.

5. What is the number of crystals per unit mass of crystals if
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 5
a) 0.01
b) 0.7
c) 0.6
d) 0.8

View Answer

Answer: a [Reason:] Number of crystals per unit mass of crystals= 4.5/fvρL3, hence N=0.01.

6. What is the number of crystals per unit mass of crystals if
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.05
a) 0.01
b) 0.7
c) 0.6
d) 100000

View Answer

Answer: d [Reason:] Number of crystals per unit mass of crystals= 4.5/fvρL3, hence N=1000000.

7. What is the number of crystals per unit mass of crystals if
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.78
a) 1.56
b) 2.34
c) 2.56
d) 0.8

View Answer

Answer: c [Reason:] Number of crystals per unit mass of crystals= 4.5/fvρL3, hence N=2.56.

8. What is the number of crystals per unit mass of crystals if
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.56
a) 5.67
b) 6.78
c) 7.11
d) 9.56

View Answer

Answer: c [Reason:] Number of crystals per unit mass of crystals= 4.5/fvρL3, hence N=7.11.

9. What is the number of crystals per unit mass of crystals if
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.67
a) 1.56
b) 7.89
c) 4.22
d) 4.15

View Answer

Answer: d [Reason:] Number of crystals per unit mass of crystals= 4.5/fvρL3, hence N=4.15.

10. What is the nucleation rate if
Mass of production of crystals C=0.5kg
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.5
volume of mother liquor in magma V= 1m3
a) 0.5
b) 1.5
c) 1.8
d) 2.7

View Answer

Answer: c [Reason:] The nucleation rate=4.5C/fvρL3V, hence rate= 1.8.

11. What is the nucleation rate if
Mass of production of crystals C=0.5kg
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.5
volume of mother liquor in magma V= 0.5m3
a) 5.4
b) 3.6
c) 1.8
d) 2.7

View Answer

Answer: b [Reason:] The nucleation rate=4.5C/fvρL3V, hence rate= 3.6.

12. What is the nucleation rate if
Mass of production of crystals C=0.5kg
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.6
volume of mother liquor in magma V= 1m3
a) 1.45
b) 1.5
c) 1.07
d) 1.04

View Answer

Answer: d [Reason:] The nucleation rate=4.5C/fvρL3V, hence rate= 1.04.

13. What is the nucleation rate if
Mass of production of crystals C=0.5kg
Volume shape factor fv= 0.5
Density of particle= 0.5kg/m3
Characteristic size of crystal L= 0.5
volume of mother liquor in magma V= 1m3
a) 0.5
b) 15
c) 1.8
d) 18

View Answer

Answer: d [Reason:] The nucleation rate=4.5C/fvρL3V, hence rate= 18.

14. What is the nucleation rate if
Mass of production of crystals C=10kg
Volume shape factor fv= 0.5
Density of particle= 5kg/m3
Characteristic size of crystal L= 0.5
volume of mother liquor in magma V= 1m3
a) 9
b) 18
c) 180
d) 36

View Answer

Answer: c [Reason:] The nucleation rate=4.5C/fvρL3V, hence rate= 180.