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# Multiple choice question for engineering

## Set 1

1. Feed should be located at?
a) Far from optimum
b) Below the optimum
c) Away from optimum
d) At optimum

Answer: d [Reason:] Feed stage location are anywhere according to pinch point where the equilibrium and striping line meets.

2. Reflux ratio should be?
a) Minimum
b) Maximum
c) Optimum
d) Can’t specified

Answer: a [Reason:] Reflux ratio should be Minimum, as the reflux ratio decrease the ease of separation gets increases as they are inversely proportional.

3. Boil Up ratio should be?
a) Minimum
b) Maximum
c) Optimum
d) Can’t specified

Answer: b [Reason:] Boil Up ratio should be Maximum, as the boil up ratio increases the difficulty of separation gets increases as they are directly proportional.

4. Sneaking up is a
a) Homologues Method
b) Homotomy Method
c) Euler’s Method
d) NR Method

Answer: b [Reason:] Sneaking up is a part of Homotomy Method. Sneak is used in the plotting of F(x) And G(x) curves which does not involve Euler’s method.

5. Degree of freedom increases, as
a) Reflux increases
b) Purity decreases
C) Purity increases
D) Reflux decreases

Answer: c [Reason:] Degree of freedom increases as Purity increases, as they are ditrectly proportional also this can be related using phase rule F =C –P+2.

6. Extreme purity is confessed to be?
a) 90.0%
b) 99.8%
c) 99.1%
d) 99.9%

Answer: b [Reason:] Extreme purity is confessed to be 99.8%, this has to be very précised even a point 0.01% error cannot be tolerated for the purity.

7. Energy input and internal flow affect each other.
a) True
b) False

Answer: a [Reason:] Input and internal flow always affect each other, the input feed can certainly vary with varying heat and mass input.

8. The end of an equilibrium curve is called as
a) Critical point
b) Triple point
c) End point
d) Single point

Answer: a [Reason:] A critical point is the end point of a phase equilibrium curve, while the point where all three phases of water coexist is called as triple point and final stages of any curve are called as end point.

9) In the below diagram, A Curve represents?

a) Final cost
b) Operating cost
c) Feed cost
d) Tray cost

Answer: d [Reason:] It represents the Total cost, the tray cost is a nonlinear and exponential relation with reflux and cost outcomes.

10. In the below diagram, B Curve represents?

a) Final cost
b) Operating cost
c) Feed cost
d) Tray cost

Answer: b [Reason:] It represents the Operating cost, the operating cost is a linear and exponential relation with reflux and cost outcomes.

## Set 2

1. The underwood’s equation, implies of using trial and error for finding
a) Θ
b) α
c) β
d) Ω

Answer: a [Reason:] We find θ which must lie between relative volatilities of the keys, while α denotes the relative volatility of components.

2. The ratio of the key components is essentially equal to their ratio in liquid feed, was given by?
a) Underwood
b) Gilliland
c) Brown-Martin
d) Fenske

Answer: c [Reason:] This method was based on the observation that a feed pinch point, Fenske is based on feed compositions of the system.

3. Colburn Method can be used to calculate the _____ in a binary system.
a) Minimum Reflux
b) Maximum Reflux
c) Minimum Trays
d) Maximum Trays

Answer: a [Reason:] Minimum reflux can be calculated by the Colburn method, Fenske’s can be used for Minimum Trays.

4. Colburn method is based on the
a) Constant Molar Overflow and relative volatility
c) Reflux ratio
d) Maximum Trays

Answer: a [Reason:] The Colburn method is an elaborate method based on assumption that Constant Molar Overflow and relative volatility.

5. A non-key component may be distributed, if it has volatility
a) Very far to one from other keys
b) Same as that of non-key
c) Very close to that of one keys
d) Constant Molar Overflow

Answer: c [Reason:] Volatility that very close to that of one keys is not disturbed, as constant molar overflow resides for the column feed assumptions.

6. If the flow rates of liquid and distillate are 150 kmol/h and 100 kmol/h. Find reflux ratio?
a) 90
b) 50
c) 15
d) 30

Answer: c [Reason:] Reflux is given by L/D = 150/100 = 15.

7. If S=8.137 and α =1.956. Then No. of stages are?
a) 13
b) 14
c) 12
d) 16

Answer: c [Reason:] As N=S/ln α = 8.137/ln 1.956 = 12.

8. The ROSE Method involves the plot of
a) 1/R vs 1/N
b) 1/S vs 1/N
c) 1/S vs 1/R
d) 1/T vs 1/P

Answer: a [Reason:] Rose curve is not a straight line given by 1/R vs 1/N, while 1/S vs 1/N is defined as the inverse Rose curve method.

9. The Ratio of optimum feed stages to total number of stages is
a) Dependent on number of stages
b) Independent of number of stages
c) Independent of total stage
d) Inversely proportional.

Answer: b [Reason:] This is mathematically explained as Fenske’s equation, which also involves relative volatility of the components.

10. The K value of Methane at 205oF is?
a) 15
b) 28
c) 16
d) 1.65

Answer: a [Reason:] Using Tabulated data as in Henry Kister (Table 2.8) it is specified, these values are based on experiments and can’t be calculated using any formula they are purely correlations.

## Set 3

1. The number of theoretical stages, depends on the
a) Stepping off the tray
b) Reflux ratio
c) Operating line
d) Flow rates

Answer: b [Reason:] The number of theoretical stages depends on the reflux ratio R = L0/D, while the reflux ratio itself depends upon the operating line.

2. When R is infinite, the slope of this rectifying becomes
a) 0
b) 1
c) 0.5
d) Can’t be specified

Answer: b [Reason:] When R is infinity, the slope of this line becomes 1, while R is zero the slope of this line reaches infinity.

3. If x=0.4 and y =0.6633 and point xD (0.9, 0.9). Then estimate Rmin
a) 0.9
b) 0.4734
c) 0.4
d) 0.66

Answer: a [Reason:] As Rmin/R+1 = (0.9-0.6633)/ (0.9/0.4) = 0.4734 then 0.4734/1-0.4734 = 0.9.

4. If distillate is 95%, and withdrawal is 4 and α=2.5. Estimate total number of tray?
a) 7.7
b) 10
c) 6.7
d) 5.7

Answer: c [Reason:] Using Fenske’s equation and subsuming values we have 2.66/log 2.5= 6.7.

5. For non-ideal cases, to calculate number of stages we use
a) Point efficiency
b) Murphree efficiency
c) Tray efficiency
d) Overall efficiency

Answer: b [Reason:] To calculate the number of stages in a non-ideal case, Murphree efficiency line is used instead of the ideal.

6. Minimum reflux ratio in a distillation column results in
a) Optimum no. of trays
b) Minimum reboiler size
c) Maximum condenser size
d) Minimum number of trays

Answer: c [Reason:] Minimum reflux ratio in a distillation column results in maximum condenser size as inversely proportional.

7. In a tray column, Murphree efficiency
a) Exceed 100%
b) Equal to 100%
c) Can’t be specified
d) Depend upon cases given

Answer: a [Reason:] In a non-ideal case, Murphree efficiency can exceed 100%, also it depends on the cases given and the feed type.

8. For value of m, the change in liquid concentration is independent of tray location if
a) L/V = 1
b) V/L =1
c) L/mV=1
d) Vm/L=1

Answer: c [Reason:] At this condition slope of operating line equals to slope of equilibrium line, i.e. m = 1 this shows the steady state operation.

9. At minimum reflux, No. stages are
a) Unity
b) Infinite
c) Zero
d) Negative

Answer: b [Reason:] Minimum reflux and stages are inversely proportional relation, while at maximum reflux the number of stages are zero.

10. Scaling up from pilot scale to industrial scale only increases
a) Feed rates
b) Reflux ratio
c) No. of stages
d) Composition

Answer: a [Reason:] There will be no effect on internal property only feed rates are increased after scaling, Only dimensionless properties change like Re, Sc and Sh.

## Set 4

1. For the light key component, Equilibrium relation is
a) yK=x
b) Kx=y
c) Depend upon trays
d) Can’t be specified

Answer: a [Reason:] Here Kx=y is the equilibrium relation, which does not depends upon the number of trays or the vice versa relation i.e. Kx=y representing x and y moles of gas and fluid.

2. If the fractional recovery of light key in the distillate is FR, then light key in the feed is
a) DxD= (FRD)+FxLK
b) DxD= (FRD)/FxLK
c) DxD= (FRD)FxLK
d) DxD= (FRD)

Answer: c [Reason:] The definition of the fractional recovery is DxD= (FRD) FxLK, while gives us the material balance on feed and distillate DxD= (FRD).

3. For multi-component systems, Underwood Equations gives
a) Minimum Reflux
b) Minimum Strip
c) Maximum Reflux
d) Minimum Trays

Answer: a [Reason:] Underwood Equations gives Minimum Reflux, Fenske’s equation gives minimum Trays and McCabe gives us minimum Reflux.

4. Gilliland Correlation is arranged to estimate the
a) Numbers of Stages
b) Numbers of Reboiler
c) Numbers of Feed
d) Numbers of Column

Answer: a [Reason:] Gilliland Correlation is arranged to estimate the Numbers of Stages at finite reflux ratio, while reboiler is only a unit piece of set.

5. Gilliland’s y intercept is given as
a) Nmin/N+1
b) N-Nmin/N+1
c) N+Nmin/N+1
d) N/N+1

Answer: b [Reason:] Gilliland represented correlation graphically as, N-Nmin/N+1 on y axis, where N is the number of stages.

6. Gilliland’s x intercept is given as
a) Rmin/R+1
b) R/R+1
c) Nmin/R+1
d) R-Rmin/R+1

Answer: d [Reason:] Gilliland represented correlation graphically as R-Rmin/R+1 on x axis, where R is the reflux ratio of the system.

7. Optimum feed-stage location, can be obtained by using
a) Gilliland correlation
b) Kirk bride correlation
c) Fenske’s correlation
d) Sorel’s correlation

Answer: b [Reason:] An approximate optimum feed-stage location, can be obtained by Equation of Kirk bride correlation while Gilliland correlation is used to plot intercepts.

8. For Multicomponent Mixtures Equilibria depend on ?
a) Pressure
b) Temperature
c) Humidity
d) Enthalpy

Answer: b [Reason:] It depends on T, which changes from stage to stage, Pressure is not the deciding criteria as it can vary from Colum to column.

9. In multicomponent distillation, the separation of components is calculated using
a) Assumed flows of species
b) Assumed flows of reflux
c) Assumed flows of Vapor
d) Assumed flows of liquid

Answer: c [Reason:] The number of plates above and below the feed is assumed, and the separation is calculated using assumed reflux.

10. Once the components are identified, in a multicomponent distillation they are called
a) Key Components
b) Mixed Components
c) Flow Components
d) Gain Components

Answer: a [Reason:] Once the components are identified, they are called Key Components, the components which are hence mixed in a single stage rate called mixed components.

## Set 5

1. Rigorous methods are only applied to
a) Small columns
b) Large columns
c) Dual columns
d) Triple columns

Answer: a [Reason:] Rigorous methods are only applied to Small columns for final design checks, whereas trial and error involves for final calculations.

2. Rigorous methods are used as primary
a) Stage calculation tools
b) Cost calculation tools
c) Control optimization tools
d) Design and optimization tools

Answer: d [Reason:] Rigorous methods are used as primary Design and optimization tools and Procuring methods are used for calculations of cost and stages.

3. An equilibrium stage that contains no feed, side products or heat exchangers is called
a) Final stage
b) Simple stage
c) First stage
d) Exit stage

Answer: b [Reason:] An equilibrium stage that contains no feed, side products or heat exchangers is called Simple stage.

4. A stage that contains more than one feed, side products or heat exchangers is called
a) Simple stage
b) Multi Stage
c) Complex stage
d) Pure stage

Answer: c [Reason:] A stage that contains more than one feed, side products or heat exchangers is called Complex stage.

5. In a multicomponent operation, i and j are
a) Variables of flow
b) Component and stage
c) Reflux and Boil up
d) Feed ratio

Answer: b [Reason:] In a multicomponent operation i and j are Component and stage, where I represents the gas phase and j as the liquid one.

6. MESH stands for?
a) Material, equilibrium, summation and heat
b) Mass, equilibrium, simulation and heat
c) Makeup, equilibrium, subject and heat
d) Material, equilibrium, summation and Height

Answer: a [Reason:] MESH stands for Material, equilibrium, summation and heat, all these components are equally important for the column specifications and design analysis.

7. When a solution is said to be formed?
a) All MESH equation are zero
b) All MESH equation are infinite
c) All MESH equation are satisfied
d) All MESH equation are unity

Answer: c [Reason:] When all MESH equation are satisfied a solution is said to be formed, when MESH are zero this represent the error in calculations.

8. Murphree equation is used for calculating?
a) Stage calculation
b) Equilibrium condition
c) Reflux ratio
d) Tray efficiency

Answer: d [Reason:] Murphree equation is used for calculating Tray efficiency and reflux ratio is calculated as L/D and equilibrium conditions given by y* = x.

9. The term KijVj/Lj is called
a) Stripping factor
b) Absorption Factor
c) Reflux Ratio
d) Boil up