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# Multiple choice question for engineering

## Set 1

1. Which one of the following is a constant reflux process?
a) Flash distillation
b) Simple distillation
c) Multicomponent distillation
d) Final distillation

Answer: b [Reason:] Simple or batch distillation is working on the constant reflux in such a distillation compositions continuously vary with time.

2. Batch distillation under constant reflux can be analyzed?
a) –dw=dD
b) dv=-dx
c) – dy=dZ
d) dX=dy

Answer: a [Reason:] –dw = dD where,W= Still moles and D= moles of distillate.

3. The initial mole Yint fraction of gas, can be obtained by
a) Xd/R+1
b) –dw=dD
c) – dy=dZ
d) R+1

Answer: a [Reason:] Yint fraction of gas can be obtained by Xd/R+1, Where Yint=value of y at x =0.

4. As the distillation proceeds, the L/V ratio
a) Constant
b) Decreases
c) Increases
d) Vanishes

Answer: c [Reason:] The distillation and the L/V ratio are directly proportional and thus as distillation proceeds L/V Increases.

5. Calculate V? If D = 52.2 moles and R is 1.64
a) 138 moles
b) 35 moles
c) 450 moles
d) 46 moles

Answer: a [Reason:] As the V = D(R+1) = 52.2 (1.64+1) = 138 moles.

6. If the area of the column is 3.61 m2 and the initial and final distilled moles are 0.95 and 0.50 with Withdrawal of 100 moles, then V is?
a) 162
b) 456
c) 78
d) 45

Answer: a [Reason:] As V= W0 (Xd – X0) (Area) = 100 (0.95-0.50)3.61 = 162 moles.

7. The Antoine equation is given as
a) ln VP = B –A/CT
b) ln VP =A – B/T
c) ln VP = B – A/T
d) ln VP = B -CA

Answer: b [Reason:] The Antoine equation is ln VP =A – B/T where A, B and C are constants and VP is the vapor pressure.

8. Find R? If Xd = 0.98 and Yi =0.647
a) 0.633
b) 0.589
c) 0.515
d) 0.25

Answer: c [Reason:] As R = Xd/ Yi – 1 = 0.98/0.647 – 1 = 0.515.

9. The Ract can be taken, as
a) 1.3Rmin
b) 1.6 Rmin
c) 2.0 Rmin
d) 3.0 Rmin

Answer: c [Reason:] For a particulate separation the actual reflux ratio is taken as to be twice the actual reflux ratio i.e. Rmin.

10. Calculate feed line q? If HV=31,067, HF=34,601 and Hl= 0
a) -0.114
b) -0.36
c) -0.556
d) 0.885

Answer: a [Reason:] As q = ( HV- HF)/( HV- Hl) = (34,067-34,601)/(34,067-0) = -0.114.

## Set 2

1. More volatile keys are defined as
a) Heavy key (H)
b) Over Key (O)
c) Light Key (L)
d) Down comer Key (D)

Answer: c [Reason:] Keys must differ in volatility more volatile is the Light Key (L), while the less volatile keys are defined as Heavy key (H).

2. Components heavier than the heavy key are finally
a) Recovered in the Condenser
b) Recovered in the bottom stream
c) Recovered in the Upsides stream
d) Not recovered

Answer: b [Reason:] Components heavier than the heavy key are finally separated at bottom stream and light key at the top.

3. For an infinite number of plates required, the desired separation
a) Hardly possible
b) Finely possible
c) Can’t be specified
d) Assumable

Answer: a [Reason:] At infinite plates for reflux ratio, the desired separation is just barely possible, while for fixed number of trays the separation can be assumed.

4. Which of the following model is best for computer simulation?
a) Auto Model
b) HYSYS Model
c) Cremer Model
d) Two parameter model

Answer: b [Reason:] For computer simulation HYSYS Model is widely used, auto model is used to design automobiles, whereas two parameter model is used in reaction operations.

5. For computer simulation, considerations were defined by
a) Richardson and Coulson
b) Robinson and Gilliland
c) Murphree and Fenske
d) Johnson and Morgan

Answer: d [Reason:] Key considerations were defined by Johnson and Morgan and Robinson and Gilliland gave the correlation of stages and Richardson and Coulson are famous chemical engineering authors.

6. For identifying misallocated feed stages, which of the following is used?
a) Key Ratios
b) Molar Ratios
c) Reflux Ratios
d) Feed Ratios

Answer: a [Reason:] Misallocated feed stages are identified using Key Ratios, while separation are identified using the feed ratios.

7. Key ratios and stages are plotted on which scale?
a) Binary scale
b) Exponential Scale
c) Semi log scale
d) Pressure scale

Answer: c [Reason:] Key ratios and stages are plotted on Semi log scale, and equilibrium relation are plotted on binary scale.

8. d/b plots are also called as
a) Key plots
b) Mole plots
c) Reflux plots
d) Non Key plots

Answer: a [Reason:] They are called as key plots always, where d is the higher key representative and b the lower one.

9. d/b plots are used when there is
a) Non key components
b) Total reflux
c) Boil up required
d) Can’t be specified

Answer: a [Reason:] The d/b plots are used when there is tight spacing on non-key components, while full withdrawal of product is called as total reflux.

10. d/b plots are
a) Exponential
b) Logarithmic
c) Linear
d) Non linear

Answer: d [Reason:] The d/b plots are frequently Nonlinear, equilibrium plots are nonlinear and diagonal plots are linear.

## Set 3

1. The allowable vapor pressure velocity, is taken to be
a) 60 to 80%
b) 50 to 60%
c) 10 to 20%
d) 30 to 40%

Answer: a [Reason:] Clearly 60 to 80 % of the flooding velocity is calculated to keep the tray out of the danger of flooding.

2. The hole diameter lies between?
a) 1/8 to 1 inch
b) 1/8 to ½ inch
c) 1/6 to ½ inch
d) ½ to 1 inch

Answer: b [Reason:] The hole diameter of an industrial tray normally lies between the 1/8 to ½ inch but can be less also.

3. Increasing the tray spacing can result in?
a) Less entrainment
b) Larger area
c) Low bubbling
d) All of the above

Answer: d [Reason:] The tray spacing allows the tolerance of more space becomes available for the descent of the liquid droplets.

4. Entrainment, can be reduced by
a) Baffles
b) Vortex
c) Clip
d) Sieve

Answer: a [Reason:] The fitting of a baffle can increase in the vapor space and thus reducing entrainment.

5. Vapor handling can be improved by?
a) Reducing perforations
b) Reducing down comer
c) Increasing Velocity
d) Removing baffles

Answer: a [Reason:] By reducing the size of the perforations the vapor handling capacity of tray is increased as well as weeping is reduced.

6. Changing old accessories with new one, the process is called as?
a) Re-fitting
b) Re-Designing
c) Re-vamping
d) Re-cycling

Answer: c [Reason:] If an existing column is required to work at the higher capacity the column is called revamped.

7. Changing of internals of a column, with more efficient ones are?
a) Retrofitting
b) Refitting
c) Revamping
d) Recycling

Answer: a [Reason:] Retrofitting is generally done to reduce energy consumption of the column, it also increases the operating cost as well.

8. For operations involving chemical reactions ________ vessels are used.
a) Perforated
b) Agitated
c) Bored
d) Plated

Answer: b [Reason:] The Agitated vessels are used when gas overcomes the reaction in fluid, as this acts as an external force to proceed fast reactions.

9. HTU is defined as?
a) Height of transfer unit
b) Height of tray unit
c) Height of tissue plant
d) Height of Plain uncovered

Answer: a [Reason:] HTU is a measure of the difficulty of separation of two components it is an important factor of distillation.

10. NTU is defined as?
a) Number of tray unit
b) Number of tissue plant
c) Number of transfer unit
d) Number of Plain uncovered

Answer: c [Reason:] NTU is a measure of the ease of separation of two components it is an important factor of distillation.

## Set 4

1. The crucial difference compared to homozeotrope distillation is that, a heteroazeotrope can be separated by?
a) Decantation
b) Depurification
c) Dehydration
d) Decansing

Answer: a [Reason:] The crucial difference compared to homoazeotropic distillation is that a heteroazeotrope can be separated easily by decantation, this also makes the process scheme simpler.

2. Which of the following equations are satisfied at azeotropic conditions?
a) Av(v) + Al(v) = 0
b) Av(v) – Al(v) = 0
c) Av(v). Al(v) = 0
d) Av(v) =Al(v)

Answer: b [Reason:] Av(v) and Al(v) are the Helmholtz energy of the vapor and liquid phases respectively, V, V0 and Vl are the total molar volume.

3. The residue curves of an n component homogenous mixture is defined by?
a) n-1 ODE
b) n-2 ODE
c) n-3 ODE
d) n ODE

Answer: a [Reason:] The residue curves of an n component homogenous mixture is defined by n-1 ODE’s, where dxi/dE and E is dimensionless warped time.

4. Permeate fluxes decrease, significantly with decreasing
a) Reflux ratio
b) Feed Concentrations
c) Boiling point
d) Bubble point

Answer: b [Reason:] Permeate fluxes decrease significantly with decreasing feed concentrations, There is a trade-off between the permeate flux and selectivity.

5. Heteroazeotropic (VLLE) distillation, often referred to as?
a) Azeotropic distillation
b) Exractive distilllaton
c) Batch Ditilation
d) Continous Distillation

Answer: a [Reason:] Heteroazeotropic (VLLE) distillation, often referred to as azeotropic distillation, involves the formation of a heteroazeotrope to affect the desired separation.

6. A greater entrainer flowrate generally, yields better
a) Reflux
b) Boil up
c) Hold up
d) Separation

Answer: d [Reason:] A greater entrainer flowrate generally yields better separation, but this increases the energy demand in both columns and increases the reboiler temperature in the extractive column.

7. Separating a maximum-boiling azeotrope using a light entrainer, this process is referred to as?
a) Re-extractive distillation
b) De-extractive distillation
c) Extractive distillation
d) Boil up distillation

Answer: a [Reason:] The same extractive distillation scheme can in principle be applied to the symmetrical system of separating a maximum-boiling azeotrope using a light entrainer and this process is referred to as re-extractive distillation.

8. The vapor-liquid equilibrium (VLE) condition which may be expressed as?
a) y = f (S, H, T)
b) y = f (P, T, x)
c) x = f (T, S)
d) y = f (J, S)

Answer: b [Reason:] Where x and y are the liquid and vapor compositions, and P and T are the system pressure and temperature, respectively T and x are not independent at the equilibrium state.

9. When y = E(x), where E is?
a) Mapping function
b) Entity function
c) Frequency function
d) Phase function

Answer: a [Reason:] E is the equilibrium mapping function that assigns a composition in the liquid phase to the corresponding equilibrium vapor phase composition, and Tbp and Tdp are the mixture boiling temperature.

10. When x = C(y), where C is?
a) Inverse function
b) Mapping function
c) Entrainment function
d) Flooding Function

Answer: a [Reason:] Here, C is the inverse equilibrium mapping function that assigns a composition in the vapor phase to the corresponding equilibrium liquid phase composition.

## Set 5

1. Extractive distillation of ethanol and water is done using?
a) Benzene
b) Ethylene glycol
c) Alcohol
d) Any acid

Answer: b [Reason:] Extractive distillation of ethanol and water using ethylene glycol as an entrainer is a classic example in the distillation literature.

2. Acetone and methanol form a binary minimum-boiling azeotrope, of about?
a) 75.8% acetone
b) 80% acetone
c) 70% acetone
d) 50% acetone

Answer: a [Reason:] Acetone and methanol form a binary minimum-boiling azeotrope of about 78.5 mole % acetone, Water is miscible and zeotropic in the whole composition space.

3. High reflux “weakens”, the effect of the?
a) Stages
b) Trays
c) Entrainer
d) Plates

Answer: c [Reason:] High reflux “weakens” the effect of the entrainer (E), there is a minimum and a maximum reflux ratio in order to achieve acceptable separation between component 1 and E.

4. Liquid reflux (L1), is used to control?
a) 1/E split
b) 1/2E split
c) 1/5E split
d) E split

Answer: a [Reason:] Liquid reflux (L1) is used to control the 1/E split in the rectifying section for the extractive middle vessel batch distillation column.

5. Entrainer feed flowrate (E), is used to control?
a) 5/6 split
b) 7/8 split
c) ½ split
d) ¾ split

Answer: c [Reason:] Entrainer feed flowrate (E) is used to control the 1/2 split in the extractive section for the extractive middle vessel batch distillation column.

6. Liquid flow out of middle vessel (LM) is used to control?
a) 2/E
b) 7/E
c) 8/E
d) 1/E

Answer: a [Reason:] Liquid flow out of middle vessel (LM) is used to control the 2/E split in the stripping section, for the extractive middle vessel batch distillation column.

7. Distillate flowrate (D) is used to control the level in?
a) Rampage
b) Reflux
c) Reboiler
d) Condenser drum

Answer: d [Reason:] Distillate flowrate (D) is used to control the level in condenser drum, for the extractive middle vessel batch distillation column.

8. Bottom flowrate (B) is used to control the level in?
a) Rampage
b) Reflux
c) Reboiler
d) Condenser drum

Answer: c [Reason:] Bottom flowrate (B) is used to control the level in reboiler, for the extractive middle vessel batch distillation column.

9. The locus of compositions that cannot be crossed by the given distillation process, is called?
a) Distillation line
b) Distillation Boundary
c) Distillation Map
d) Distillation region

Answer: b [Reason:] The locus of compositions that cannot be crossed by the given distillation process, the existence and location of such boundaries depend critically on the type of distillation in question.

10. The locus of points in the composition space where the temperature for a given mixture at vapor-liquid equilibrium is constant, is called?
a) Isotherm
b) Paratherm
c) Dual nature
d) Final-therm