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## Interview MCQ Set 1

1. Pervaporation method involves
a) Removal of ions
b) Production of potable water
c) Purification of aqueous streams
d) Separation and concentration of liquid mixture.

Answer: d [Reason:] Pervaporation is process of separation and concentration of liquid mixture.

2. When is the pervaporation preferred?
a) When feed solution is dilute in main permeant
b) When feed solution is rich in main permeant
c) When feed solution is dilute in retentate
d) When feed solution is rich in retentate

Answer: a [Reason:] Pervaporation is preferred when the feed solution is dilute in main permeant. If the solution is rich in permeant then more number of membrane stages may be required.

3) Which type of membrane is required for water permeation?
a) Hydrophobic
b) Hydrophilic
c) Semipermeable
d) Permeable

Answer: b [Reason:] When water is to be permeated, hydrophilic membrane is required making the selection of membranes an important factor.

4. What factor is unaccountable in gas permeation?
a) Temperature
b) Polymer
c) Permeant
d) Concentration of permeants

Answer: d [Reason:] The concentration of permeants is not dependent in gas permeation.

5. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 2
b) 4
c) 5
d) 7

Answer: a [Reason:] Since Permeance= N/(YxV.P-yP), Permeance= 10/(25-20)=2.

6. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.6, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 2
b) 4
c) 5
d) 1

Answer: d [Reason:] Since Permeance= N/(YxV.P-yP), Permeance= 10/(30-20)=1.

7. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=10, x= 0.4
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.5
Total permeant pressure P= 80
a) 20
b) 40
c) 50
d) 0.03

Answer: a [Reason:] Since Permeance= N/(YxV.P-yP), Permeance= 10/(400-40)=0.03.

8. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 60
a) 2
b) 41
c) 1
d) 7

Answer: c [Reason:] Since Permeance= N/(YxV.P-yP), Permeance= 10/(25-15)=1.

9. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 200
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 1.33
b) 2.55
c) 5.44
d) 7

Answer: a [Reason:] Since Permeance= N/(YxV.P-yP), Permeance= 10/(50-20)=1.33.

10. Incorrect statement about pervaporation is
a) Low cost
b) Independent of vapour/liquid equilibrium
c) Suitable for heat sensible product
d) Require high temperature and high pressure.

Answer: d [Reason:] Pervaporation does not require high temperature and high pressure.

## Interview MCQ Set 2

1. How is the distribution among two or more phases at equilibrium determined by?
a) Application of entropy
b) Application of Newton’s laws of motion
c) Application of Gibbs free energy
d) Application of force

Answer: c [Reason:] G (T,P, N1, N2…..) is used to determine the extent of distribution in two or more phases.

2. At equilibrium the total Gibb’s free energy for all phases is
a) Minimum
b) Maximum
c) Infinity
d) Zero

Answer: a [Reason:] At equilibrium the total Gibbs’ free energies are minimum.

3. The chemical potential of a species is:
a) Different in all phases at chemical equilibrium
b) Same in all phases at chemical equilibrium
c) Different in all phases at physical equilibrium
d) Same In all phases at equilibrium

Answer: d [Reason:] µ i = µi (1) + µ i (2) …+ µ i (N) . Thus the chemical potential is same in all phases at physical equilibrium.

4. The formula for partial fugacity is:
a) F i =Cexp(µ i /RT)
b) F i = Cexp(µ i )
c) F i =exp(µ i )
d) F i =C(µ i /RT)

Answer: a [Reason:] The partial fugacity which is like pseudo pressure has a formula of F i =Cexp (µ i /RT).

5. What is the phase equilibrium ratio?
a) Ratio of heat of species in two phases at equilibrium
b) Ratio of temperature of species in two phases at equilibrium
c) Ratio of mole fractions of species in two phases at equilibrium
d) Ratio of equilibrium concentration of species in two phases at equilibrium.

Answer: c [Reason:] Phase equilibrium ratio is the ratio of mole fractions of species in two phases at equilibrium.

6. For a liquid-liquid case, what is phase equilibrium ratio?
a) Ratio of mole fractions of species in two phases at equilibrium
b) Ratio of distribution or partition coefficient
c) Ratio of equilibrium constant
d) Ratio of heat of supply

Answer: b [Reason:] K Di = x i (1) /x i (2).

7. Which equation is to be used for hydrocarbon and light gas mixture from cryogenic temperatures to critical region?
a) K i = ϕ iL / ϕ iV
b) K i = γ iL ϕiL/ ϕ iV
c) K i = P i s /P
d) K iiL P i s /P

Answer: a [Reason:] Here the equation of state is used.

8. Which equation is used for all mixtures from ambient to critical temperature?
a) K i = ϕ iL / ϕ iV
b) K i = γ iL ϕiL/ ϕ iV
c) K i = P i s /P
d) K iiL P i s /P

Answer: b [Reason:] Here the activity coefficient is also multiplied.

9. Which equation is used for ideal solutions at near ambient pressure?
a) K i = ϕ iL / ϕ iV
b) K i = γ iL ϕiL/ ϕ iV
c) K i = P i s /P
d) K iiL P i s /P

Answer: c [Reason:] Here, Roult’s law is used.

## Interview MCQ Set 3

1. Precipitation is opposite of what separation technique?
a) Distillation
b) Solution crystallization
c) Melt crystallization
d) Zone melting

Answer: b [Reason:] In solution crystallization a solution is cooled or partially to make the solution exceed in its solubility sufficiently to make the solute crystallize. So it is the opposite of solution crystallization.

2. Precipitation is applicable for what types of solutes?
a) Insoluble
b) Soluble
c) Sparingly soluble
d) Both insoluble and soluble

Answer: c [Reason:] Precipitation is applicable only for sparingly soluble solutes so that they precipitate out easily.

3. Why does the resulting shapes maybe far away from what corresponds to minimum gibbs free energy?
a) Because they come out of a solution
b) Because they might contain moisture
c) Because they are formed at considerable super saturation
d) Because they contain impurities from solution

Answer: c [Reason:] The resulting shapes maybe far away from what corresponds to minimum gibbs free energy which depends on particle size and interfacial tension b Because they are formed at considerable super saturation.

4. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 30 seconds, what is the number of crystals per unit volume of mother liquor?
a) 6*108
b) 6*109
c) 1.5*109
d) 1.5*108

Answer: b [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 6*109.

5. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 3seconds, what is the number of crystals per unit volume of mother liquor?
a) 6*108
b) 6*109
c) 1.5*109
d) 1.5*108

Answer: a [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 6*108.

6. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 75seconds, what is the number of crystals per unit volume of mother liquor?
a) 6*108
b) 6*109
c) 1.5*109
d) 1.5*108

Answer: c [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 1.5*109.

7. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 40 seconds, what is the number of crystals per unit volume of mother liquor?
a) 8*108
b) 8*109
c) 9*109
d) 9*108

Answer: b [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 8*109.

8. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 45 seconds, what is the number of crystals per unit volume of mother liquor?
a) 8*108
b) 8*109
c) 9*109
d) 9*108

Answer: c [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 9*109.

9. If the nucleation rate is Bo=6.67*108nuclei/Ls and the induction time T= 30 seconds, what is the number of crystals per unit volume of mother liquor?
a) 6*108
b) 6*109
c) 6*1010
d) 6.67*109

Answer: c [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 6*1010.

10. If the nucleation rate is Bo=2*108nuclei/Ls and the induction time T= 12 seconds, what is the number of crystals per unit volume of mother liquor?
a) 23*108
b) 6*109
c) 56*109
d) 24*108

Answer: d [Reason:] Number of crystals per unit volume of mother liquor= Bo*T= 24*108.

## Interview MCQ Set 4

1. What does the term absolute humidity mean?
a) Moisture content of a gas by mass
b) Moisture content of a gas by moles
c) Ratio of humidity to humidity at saturation
d) Temperature at which moisture begins to condense when it is cooled

Answer: a [Reason:] The term absolute humidity or mass humidity means the moisture content of a gas by mass. It is expressed as the ratio of Mass of water multiplies by partial pressure of water to the mass of air multiplied by remaining pressure.

2. What does the term molal humidity mean?
a) Moisture content of a gas by mass
b) Moisture content of a gas by moles
c) Ratio of humidity to humidity at saturation
d) Temperature at which moisture begins to condense when it is cooled

Answer: b [Reason:] The term molal humidity means the moisture content of a gas by mass. It is expressed as the ratio of partial pressure of water to remaining pressure.

3. What does the term percent saturation mean?
a) Moisture content of a gas by mass
b) Moisture content of a gas by moles
c) Ratio of humidity to humidity at saturation
d) Temperature at which moisture begins to condense when it is cooled

Answer: c [Reason:] The term percent saturation refers to ratio of humidity to humidity at saturation.

4. What does the term dew-point temperature mean?
a) Moisture content of a gas by mass
b) Moisture content of a gas by moles
c) Ratio of humidity to humidity at saturation
d) Temperature at which moisture begins to condense when it is cooled

Answer: d [Reason:] The term dew point temperature refers to the temperature at which moisture begins to condense when it is cooled.

5. What does the term humid volume refer to?
a) Specific heat of moisture gas mixture per unit mass of moisture free gas
b) Volume of moisture gas mixture per unit mass of moisture free gas
c) Enthalpy of moisture gas mixture per unit mass of moisture free gas
d) Temperature attained when a gas is saturated with moisture in an adiabatic process

Answer: b [Reason:] The term humid volume means the volume of moisture gas mixture per unit mass of moisture free gas.

6. What does the term humid heat refer to?
a) Specific heat of moisture gas mixture per unit mass of moisture free gas
b) Volume of moisture gas mixture per unit mass of moisture free gas
c) Enthalpy of moisture gas mixture per unit mass of moisture free gas
d) Temperature attained when a gas is saturated with moisture in an adiabatic process

Answer: a [Reason:] The term humid heat means the heat of moisture gas mixture per unit mass of moisture free gas.

7. What does the term total enthalpy refer to?
a) Specific heat of moisture gas mixture per unit mass of moisture free gas
b) Volume of moisture gas mixture per unit mass of moisture free gas
c) Enthalpy of moisture gas mixture per unit mass of moisture free gas
d) Temperature attained when a gas is saturated with moisture in an adiabatic process

Answer: c [Reason:] The term total enthalpy means the enthalpy of moisture gas mixture per unit mass of moisture free gas.

8. What does the term adiabatic saturation temperature refer to?
a) Specific heat of moisture gas mixture per unit mass of moisture free gas
b) Volume of moisture gas mixture per unit mass of moisture free gas
c) Enthalpy of moisture gas mixture per unit mass of moisture free gas
d) Temperature attained when a gas is saturated with moisture in an adiabatic process

Answer: d [Reason:] The term adiabatic saturation temperature means the temperature attained when a gas is saturated with moisture in an adiabatic process.

9. What does dry bulb temperature mean?
a) Temperature of mixture
b) Steady state temperature attained by a wet bulb thermometer
c) Temperature attained when a gas is saturated with moisture in an adiabatic process
d) The temperature of air having no moisture

Answer: a [Reason:] Dry bulb temperature means the temperature of the mixture.

10. What does wet bulb temperature mean?
a) Temperature of mixture
b) Steady state temperature attained by a wet bulb thermometer
c) Temperature attained when a gas is saturated with moisture in an adiabatic process
d) The temperature of air having no moisture

Answer: b [Reason:] Wet bulb temperature means the steady state temperature attained by a wet bulb thermometer.

## Interview MCQ Set 5

1. If the absolute humidity is 0.03
The mass of moisture free air is 50g
The mass of moisture is 25g
What is the molal humidity?
a) 0.03
b) 0.06
c) 0.04
d) 0.1

Answer: b [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.06.

2. If the absolute humidity is 0.02
The mass of moisture free air is 50g
The mass of moisture is 25g
What is the molal humidity?
a) 0.03
b) 0.06
c) 0.04
d) 0.1

Answer: c [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.04.

3. If the absolute humidity is 0.02
The mass of moisture free air is 50g
The mass of moisture is 10g
What is the molal humidity?
a) 0.03
b) 0.06
c) 0.04
d) 0.1

Answer: d [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.1.

4. If the absolute humidity is 0.03
The mass of moisture free air is 75g
The mass of moisture is 25g
What is the molal humidity?
a) 0.08
b) 0.15
c) 0.09
d) 0.21

Answer: c [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.09.

5. If the absolute humidity is 0.07
The mass of moisture free air is 48g
The mass of moisture is 16g
What is the molal humidity?
a) 0.08
b) 0.15
c) 0.09
d) 0.21

Answer: d [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.21.

6. If the absolute humidity is 0.075
The mass of moisture free air is 50g
The mass of moisture is 25g
What is the molal humidity?
a) 0.08
b) 0.15
c) 0.09
d) 0.21

Answer: b [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.15.

7. If the absolute humidity is 0.04
The mass of moisture free air is 50g
The mass of moisture is 25g
What is the molal humidity?
a) 0.08
b) 0.15
c) 0.09
d) 0.21

Answer: a [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.08.

8. If the absolute humidity is 0.03
The mass of moisture free air is 40g
The mass of moisture is 10g
What is the molal humidity?
a) 0.08
b) 0.15
c) 0.12
d) 0.21

Answer: c [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.12.

9. If the absolute humidity is 0.08
The mass of moisture free air is 50g
The mass of moisture is 12.5g
What is the molal humidity?
a) 0.08
b) 0.02
c) 0.32
d) 0.76

Answer: c [Reason:] Combining the formula of absolute humidity H= Mpa/Mb(p-pa) and molal humidity Hm=pa/p=pa, Hm= H*Ma/Mb=0.32.

10. If the absolute humidity is 0.06
The mass of moisture free air is 50g
The mass of moisture is 25g
What is the molal humidity?
a) 0.33
b) 0.12
c) 0.14
d) 0.18