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Interview MCQ Set 1

1. Solvent extraction is more effective when the extraction is repeated with:
a) Extra solvent
b) Large solvent
c) Small solvent
d) No solvent

View Answer

Answer: c [Reason:] Solvent extraction is more effective when the extraction is repeated with small solvent.

2. When the component has a small value of K, it is supposed to have an affinity for:
a) Mobile phase
b) No phase
c) Stationary phase
d) Whole solution

View Answer

Answer: c [Reason:] The component has a small value of K, it is supposed to have an affinity for stationary phase.

3. What is the use of ether layer?
a) To separate organic impurities
b) To separate inorganic impurities
c) To separate fibres
d) TO separate solvent

View Answer

Answer: a [Reason:] Since ether is a non-polar compound, its layer is used to separate organic impurities.

4. A mobile phase cannot be a :
a) Gas
b) Solid
c) Liquid
d) Solid or gas

View Answer

Answer: b [Reason:] A mobile phase has to flow and hence it should not be a solid.

5. What is the representation of distribution coefficient?
a) S
b) H
c) G
d) K

View Answer

Answer: d [Reason:] The distribution coefficient is denoted by K.

6. What is the colour post extraction of iodine?
a) Blue
b) Indigo
c) Purple
d) Red

View Answer

Answer: c [Reason:] The colour after extracting iodine is purple.

7. The dispersed phase is also called as:
a) Non-continuous phase
b) Continuous phase
c) Dis-continuous phase
d) Gas phase

View Answer

Answer: c [Reason:] The dispersed phase is also called as dis-continuous phase, the other phase being continuous phase.

8. What is true about mixer settlers?
a) Two liquid phases mixed with impellers and separated by gravity induced separation.
b) Two liquid phases unmixed, and magnetic separation carried out
c) Two liquid phases are mixed by impellers, and separated using magnetic separation
d) Two liquid phases are heated to mix, and gravity induced separation is carried out

View Answer

Answer: a [Reason:]” In mixer settlers, two liquid phases mixed with impellers and separated by gravity induced separation.

9. The dispersed phase is:
a) Continuous
b) Heavier
c) Lighter
d) May be heavier or lighter

View Answer

Answer: d [Reason:] The dispersed phase formed by mixing maybe a heavier or a lighter phase.

10. What is the major problem in settlers?
a) Colour of the two phases may be same
b) The two phases may not be visible
c) Emulsification in the mixing wheel
d) The size of dispersed particles can be large

View Answer

Answer: c [Reason:] If the agitation is very intense, then the size of particles can reduce to 1 to 1.5 micrometers. Thus there could be emulsification, and it is problematic.

Interview MCQ Set 2

1. Which is the simple and the oldest technique for solvent extraction?
a) Spray column
b) Packed column
c) Plate column
d) Decanter

View Answer

Answer: a [Reason:] Spray column is the simplest and oldest technique for solvent extraction.

2. Why are spray columns rarely used?
a) High cost
b) High efficiency
c) More size of equipment required
d) Due to axial dispersion

View Answer

Answer: d [Reason:] Axial dispersion is so serious that with an increase in diameter-length ratio the continuous phase completely disperses.

3. How does packing the column help?
a) Lessens the mass transfer
b) Increases the mass transfer by not breaking the large drops
c) Decreases the interfacial area
d) Increases the mass transfer by breaking the large droplets thus increasing interfacial area

View Answer

Answer: d [Reason:] The packing columns minimize the axial dispersion and help by increasing the mass transfer by breaking the large droplets thus increasing interfacial area.

4. Why is HETP larger than for staged devices?
a) To avoid overflow
b) To avoid back-mixing
c) To avoid the cost increment
d) To get full efficiency

View Answer

Answer: b [Reason:] To avoid back-mixing, HETP is larger for staged devices thus packed columns are used only when few stages are required.

5. What is the use of plate columns?
a) Increases axial mixing
b) Reduces axial mixing by packing columns
c) Reduces axial mixing and promotes a stage-wise type of contact
d) Reduces the cost

View Answer

Answer: c [Reason:] Since it is a shape of a plate, there is a stage-wise contact and also axial mixing is reduced.

6. Why are the extraction rates in sieve plate columns high?
a) Because the dispersed droplets coalesce and reform on each plate
b) Because the dispersed droplets don’t coalesce and reform on each plate
c) Because the dispersed droplets coalesce and not reform on each plate
d) Because the dispersed droplets neither coalesce nor reform on each plate

View Answer

Answer: a [Reason:] Since the dispersed droplets coalesce and reform on each plate, the extraction rates in sieve plate columns high.

7. How is agitation not induced in columns?
a) Oscillating pulse to liquid
b) Rotating agitators
c) By moving plates back and forth
d) By using mixers

View Answer

Answer: d [Reason:] Mixers are not used in columns.

8. How agitation is achieved in the scheibel column?
a) Liquid phases are contacted in fixed intervals by unbafled, flat bladed, turbine type agitators
b) By moving plates
c) By hands
d) Gravity separation

View Answer

Answer: a [Reason:] Liquid phases are contacted in fixed intervals by unbafled, flat bladed, turbine type agitators in scheibel column.

9. What type of agitator is rotating disk agitator?
a) Rotating agitator
b) By moving plates
c) By hands
d) Gravity separation

View Answer

Answer: a [Reason:] A disk agitator is a rotating agitator.

Interview MCQ Set 3

1. Which of the following is a characteristic of a horizontal tube evaporator?
a) Agitation is provided only by bubbles leaving the evaporator as vapor
b) The tube bundle is arranged vertically, with the solution inside the tubes condensing outside
c) To handle viscous solution a pump is used to force liquid upwards
d) Also called short vertical tube evaporator

View Answer

Answer: a [Reason:] Agitation is provided by the bubbles leaving the evaporator as bubbles in horizontal tube evaporator.

2. Which of the following is not an assumption in the evaporator model?
a) The feed has only one volatile components
b) Only the latent heat of vaporization is available for heating the solution
c) Boiling action in heat exchanger ensures perfect mixing
d) Overall temperature driving force is the temperature that of saturated steam

View Answer

Answer: d [Reason:] Overall temperature driving force is not the temperature of the saturated steam. It is the difference at which the steam enters and the thick liquid concentrate leaves. Hence it is Ts-Tp.

3. What is the mass flow rate of the heating steam is
Internal energy U= 500J
Area= 2m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=1000J
a) 2Kg
b) 3Kg
c) 20Kg
d) 30Kg

View Answer

Answer: c [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 20Kg.

4. What is the mass flow rate of the heating steam is
Internal energy U= 500J
Area= 2m2
Temperature driving force is Ts-Tp 30oC
Latent heat of vaporization is Hvap=1000J
a) 2Kg
b) 3Kg
c) 20Kg
d) 30Kg

View Answer

Answer: d [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 30Kg.

5. What is the mass flow rate of the heating steam is
Internal energy U= 500J
Area= 2m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=10000J
a) 2Kg
b) 3Kg
c) 20Kg
d) 30Kg

View Answer

Answer: a [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 2Kg.

6. What is the mass flow rate of the heating steam is
Internal energy U= 500J
Area= 3m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=10000J
a) 2Kg
b) 3Kg
c) 20Kg
d) 30Kg

View Answer

Answer: b [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 3Kg.

7. What is the mass flow rate of the heating steam is
Internal energy U= 400J
Area= 4m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=1000J
a) 32Kg
b) 36Kg
c) 58Kg
d) 65Kg

View Answer

Answer: a [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 32Kg.

8. What is the mass flow rate of the heating steam is
Internal energy U= 300J
Area= 6m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=1000J
a) 43Kg
b) 36Kg
c) 67Kg
d) 87Kg

View Answer

Answer: b [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 36Kg.

9. What is the mass flow rate of the heating steam is
Internal energy U= 1950J
Area= 2m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=1000J
a) 32Kg
b) 36Kg
c) 58Kg
d) 30Kg

View Answer

Answer: c [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 58Kg.

10. What is the mass flow rate of the heating steam is
Internal energy U= 400J
Area= 2m2
Temperature driving force is Ts-Tp 20oC
Latent heat of vaporization is Hvap=1000J
a) 16Kg
b) 32Kg
c) 260Kg
d) 36Kg

View Answer

Answer: a [Reason:] M= UA(Ts-Tp)/Hvap, hence m= 16Kg.

Interview MCQ Set 4

1. Which of the following is not a commonly used solvent?
a) Acetone
b) Hexane
c) Iso-butyl keton
d) Acetaldehyde

View Answer

Answer: d [Reason:] Acetaldehyde is not a commonly used solvent.

2. The cost of solvent extraction is how many times more than distillation?
a) 20
b) 30
c) 50
d) 60

View Answer

Answer: d [Reason:] The cost of solvent extraction is 60 times more than distillation.

3. How can the partition coefficient be increased?
a) By increasing the feed
b) By decreasing the feed
c) By changing pH
d) By increasing chemical potential

View Answer

Answer: c [Reason:] By changing the pH the chemical potential can be reduced hence the partition coefficient can be increased.

4. Because partition coefficients of some solvents are unfavorably low _______ has received much attention.
a) Extractive reaction
b) Reactive extraction
c) Distillation
d) Fractional distillation

View Answer

Answer: b [Reason:] Because partition coefficients of some solvents are unfavorably low reactive extraction has received much attention.

5. What can be used to enhance the extraction of polar zwitter ions?
a) Hydrogen bonding
b) Acid-base pairing
c) Formation of ion pair
d) Addition of surfactant

View Answer

Answer: a [Reason:] High hydrogen bonding will lead to high extraction of polar zwitter ions.

6. How is the organic partitioning of a cation or an anion enhanced?
a) Hydrogen bonding
b) Acid-base pairing
c) Formation of ion pair
d) Addition of surfactant

View Answer

Answer: c [Reason:] The organic portioning of a cation or anion is dramatically enhanced by formation of ion pair between target species and complementary ion-pair agent.

7. How can competitive water and mineral salts be removed?
a) Hydrogen bonding
b) Acid-base pairing
c) Formation of ion pair
d) Addition of surfactant

View Answer

Answer: b [Reason:] Acid-base pairing permits the removal of competitive water that conatins mineral salts and minerals added to alter pH.

8. What effect does increasing temperature have on KD?
a) Increases
b) Decreases
c) First increases then decreases
d) First decreases then increases

View Answer

Answer: b [Reason:] Increasing temperature decreases the kD value.

9. What happens after critical micelle concentration CMC?
a) Micelles stop forming
b) Micelles cannot form
c) Micelles start forming
d) Solubility is maximum

View Answer

Answer: c [Reason:] Above CMC micelles start forming.

10. How are reverse micelles formed?
a) By adding surfactant
b) By removing surfactant
c) By adding solvent
d) By removing solvent

View Answer

Answer: a [Reason:] By adding solvent above CMC< reverse micelles can be formed.

Interview MCQ Set 5

1. Which of the following is a correct equation of energy balance?
a) ∑out of system nh+Q+Ws – ∑insystem nh+Q+Ws=0
b) ∑out of system nh+Ws- ∑insystem nh+Q+Ws=0
c) ∑out of system nh+Q+Ws – ∑insystem nh+Ws=0
d) ∑out of system nh+Ws – ∑insystem nh+Ws=0

View Answer

Answer: a [Reason:] Heat giver or taken and shaft work also must be taken into account.

2. Which of the following is a correct equation for entropy balance?
a) ∑out of system (nS+Q/Ts) – ∑insystem (nS)=0
b) ∑out of system (nS+Q/Ts) – ∑insystem (nS+Q/Ts)=ΔSr
c) ∑out of system (nS) – ∑insystem (nS+Q/Ts)=ΔSr
d) ∑out of system (nS+Q/Ts) – ∑insystem (nS+Q/Ts)=0

View Answer

Answer: b [Reason:] Initial entropy minus final entropy gives the difference in the entropy.

3. What is the formula for minimum work of separation?
a) ∑out of system (nb) – ∑insystem (nb)=Ws
b) ∑out of system (nb) – ∑insystem (nb)=0
c) ∑out of system (nb) – ∑insystem (nb)= ΔSr
d) ∑out of system (nb) – ∑insystem (nb)=Δnb

View Answer

Answer: a [Reason:] The difference of the molar availabilities gives the minimum work of separation.

4. What is the formula for efficiency?
a) η = Wmin /(LW + Wmax)
b) η = Wmax /(LW + Wmax)
c) η = Wmin /(LW + Wmax)
d) η = Wmin /( Wmax)

View Answer

Answer: c [Reason:] Only Wmin is considered and lost work is considered.

5. What is the maximum of energy converted to shaft work if stream is taken to reference state?
a) Gibbs energy
b) Availability function
c) Entropy
d) Change in entropy

View Answer

Answer: b [Reason:] b = h – tS the availability function which the maximum energy converted to shaft work.

6. What is the formula for lost work?
a) LW = h- TΔS
b) LW = T0 – TΔSirr
c) LW = T0 ΔSirr
d) LW = T0 – Sirr

View Answer

Answer: c [Reason:] The multiplication in the absolute temperature and the change in entropy give the lost work.

7. What is the magnitude of lost work not dependent upon?
a) Process irreversibilities
b) Fluid friction
c) Mass transfer due to finite concentration
d) Mass transfer due to finite temperature driving forces

View Answer

Answer: d [Reason:] Mass transfer is not affected by finite temperature driving forces; hence it is a wrong option.

8. Why does the reduce in lost work have limitation?
a) Equipment size decreases
b) Equipment size increases
c) Flow rate decreases
d) Flow rate increases

View Answer

Answer: b [Reason:] As the driving forces decrease to reduce lost work, the equipment size increases.

9. What is the lost work is absolute temperature is 303K and the change in entropy is 1000KJ/h-k
a) 697KJ/h-k
b) 303000KJ/h
c) 3030KJ/h
d) 30300KJ/h-k

View Answer

Answer: b [Reason:] LW = T0 ΔSirr.

10. If the minimum work of separation is 100KJ and the lost work is 1000KJ, what is the efficiency of separation process?
a) 10%
b) 11%
c) 9.09%
d) 11.11%

View Answer

Answer: c [Reason:] η = Wmin/(LW + Wmax).