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Machine Design MCQ Set 1

1. At what feed condition the slope of q line is infinity?
a) Saturated vapour
b) Saturated liquid
c) Superheated vapour
d) None of the mentioned

View Answer

Answer: b [Reason:] At saturated liquid the enthalpy of feed and the liquid is same so q=1 and slope = infinity.

2. Find the feed condition from the below distribution curve.
a) Saturated vapour
b) Saturated liquid
c) Superheated vapour
d) None of the mentioned

View Answer

Answer: c [Reason:] Since the slope of the q-line is between 1 and 0 it is a superheated vapour.

3. In an operation the slope of the q-line is found to be 0; then the enthalpy of feed equals enthalpy of _____________
a) Liquid
b) Vapour
c) Mixture
d) None of the mentioned

View Answer

Answer: b [Reason:] Slope of q line = q/q-1 If the enthalpy of feed and vapour are equal then the q becomes zero; q line also becomes zero.

4. Consider a saturated liquid-vapour mixture, if the liquid flow rate inside the enriching and the stripping section of a fractionator is 50 and 40 mol/hr. Also the feed rate is 10 mol/hr. Find the feed condition.
a) Saturated vapour
b) Saturated liquid
c) Superheated vapour
d) None of the mentioned

View Answer

Answer: b [Reason:] q= 50-40/10 = 1; then the feed condition is a saturated liquid.

5. Find the liquid vapour compositions.
mass-transfer-questions-answers-flash-vaporization-line-q5
a) 0.5-Liquid & 0.5-Vapour
b) 0.6-Liquid & 0.4-Vapour
c) 0.4-Liquid & 0.6-Vapour
d) 0.5-Liquid & 0.4-Vapour

View Answer

Answer: c [Reason:] From the feed condition we can estimate that the feed has a mixture of liquid and vapour. From the distribution diagram, the vapour composition is 60% and the liquid composition is 40%.

6. At what feed condition the slope of the flash vaporization line becomes 0?
a) Saturated vapour
b) Saturated liquid
c) Superheated vapour
d) None of the mentioned

View Answer

Answer: a [Reason:] For a saturated vapour, the enthalpy of feed and the enthalpy of vapour is same so the value of q= 0; slope of q-line is 0.

7. The point where the operating line and the equilibrium line meets in distillation methods is known as
a) Plait point
b) Q point
c) Pinch point
d) None of the mentioned

View Answer

Answer: c [Reason:] At the pinch point, separation is not possible since it requires infinite number of trays in the enriching section if operating and equilibrium line meets.

8. Find the exact q line for the saturated liquid from the distribution diagram,
mass-transfer-questions-answers-flash-vaporization-line-q8
a) op
b) oq
c) or
d) pr

View Answer

Answer: a [Reason:] For the saturated liquid, slope of q-line should be infinity.

9. The equilibrium composition of liquid and vapour in a feed can be identified by,
a) intersection of q line with equilibrium line
b) intersection of q line with operating line
c) intersection of operating line with equilibrium line
d) None of the mentioned

View Answer

Answer: a [Reason:] If the value of q is between 0 and 1 then the feed has both vapour and liquid. Then the compositions can be identified by intersecting q-line with operating line.

10. If the feed enters the distillation column at its dew point, then the slope of the Flash vaporization operating line is
a) 0
b) 1
c) Between 0 and 1
d) Infinity

View Answer

Answer: a [Reason:] If the feed at dew point means the feed condition is saturated vapour so the enthalpy of feed is same as the enthalpy of the vapour. Therefore the slope of the Q-line is 0. Since Q-line is the Flash vaporization operating line.

Machine Design MCQ Set 2

1. In a certain process, there is a variation in the driving force between the phases, such process is
a) Batch process
b) Semi-batch process
c) Continuous process
d) Isothermal process

View Answer

Answer: a [Reason:] In a batch process, concentration changes with time results in varying in driving force.

2. Look out the figure below
mass-transfer-questions-answers-freshers-q2
At the position (X), which of the following will be remains same as it enters into the process.
a) Non-diffusing solvent
b) Non-diffusing solute
c) Diffusing solvent
d) Diffusing solute

View Answer

Answer: a [Reason:] Only the solute gets transfer from the respective phases. All the non-diffusing solvent remains same as it in the both entering phases.

3. Find the operating line slope
mass-transfer-questions-answers-freshers-q3
Where, X,Y- concentration in mole ratio of liquid and gas phase
x,y-concentration in mole fraction
Gs,Ls- mole free basis( non-diffusing solvent)
a) Ls/Gs
b) –Ls/Gs
c) Gs/Ls
d) –Gs/Ls

View Answer

Answer: b [Reason:] Gs(Y1)+Ls(X1)= Gs(Y2)+Ls(X2) Gs(Y1-Y2)= Ls(X2-X1) Y2-Y1= -Ls/Gs(X2-X1) Slope of the operating line is –Ls/Gs

4. In a concurrent process, the entering and leaving stream of the liquid phase concentrations in terms mole ratio is 0.25 and 0.45 also the entering and leaving stream concentration of the gas phase in terms mole ratio is 0.4 and 0.6
Find the slope of the operating line.
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: a [Reason:] -Ls/Gs= 0.6-0.4/(0.45-0.25) = 1

5. Assume an ideal solution with pure component A, has an vapour pressure of 300 mmHg and the total pressure of 1atm. The concentration in terms of mole ratio is
a) 0.65
b) 0.28
c) 0.39
d) None of the mentioned

View Answer

Answer: a [Reason:] According to Rauolt’s law, for an ideal solution Total pressure= concentration x vapour pressure Concentration in mole fraction=300/760 =0.39 Concentration in mole ratio = 0.39/(1-0.39)=0.65

6. The figure given below is a single stage ideal co- current process of solute transfer from liquid to gas phases.
mass-transfer-questions-answers-freshers-q6
a) True
b) False

View Answer

Answer: a [Reason:] if the operating line touches the equilibrium line then the stage is an ideal one. Also here only single operating line so it is a single stage.

7. Find the abscissa and ordinates of the graph
mass-transfer-questions-answers-freshers-q7
If X,Y –Concentration in mole ratio
x,y- Concentration in mole fraction
a) X,y
b) X,Y
c) x,y
d) x,Y

View Answer

Answer: c [Reason:] In the diagram, the operating line is a curve, only if the concentration is expressed in mole fraction the operating line is a curve.

8. The operating line will be straight if its concentrations are represented in mole ratio.
a) True
b) False

View Answer

Answer: a [Reason:] The non- diffusing solute remains same throughout the process. So there is a straight operating line.

9. If the whole liquid and gas flow rates are same, we can use the mole fraction for getting straight operating line
a) True
b) False

View Answer

Answer: a [Reason:] If the flow rates are same, the non- diffusing solvent rates also same as the normal flow rate. So it is possible to use mole fraction for the representation of the operating line.

10. Name of the line PR and QT
mass-transfer-questions-answers-freshers-q10
If X, Y – are represented in mole ratio
a) Interface line
b) Driving force line
c) Parallel line
d) Normal line

View Answer

Answer: b [Reason:] The distance from the Interphase is known as Driving force line.

Machine Design MCQ Set 3

1. Gas absorption is the process of transferring solute component from liquid solvent to gas mixture.
a) True
b) False

View Answer

Answer: b [Reason:] Solute transfer from liquid to gas is known as stripping or desorption. The solute transfer of gas to liquid is known as Absorption.

2. The equilibrium characteristics of the solubility of gas in liquid helps to determine the
a) Rate
b) Concentration
c) Time
d) No existence of equilibrium characteristics

View Answer

Answer: a [Reason:] The equilibrium diagram helps to determine the flux with the help of mass transfer co-efficient and concentration gradient.

3. Solubility of a gas increases with increase in temperature.
a) True
b) False

View Answer

Answer: b [Reason:] As per the equilibrium solubility curve, if the temperature increases partial pressure increases resulting in decreasing solubility.

4. Which of the following is not an example of ideal solution?
a) Solution of benzene in toluene
b) Solution of ethyl and propyl alcohol
c) Paraffin hydrocarbon gas in paraffin oil
d) Solution of isobutane and olefins

View Answer

Answer: d [Reason:] Only adjacent homologous series falls in ideal solution category. Here, isobutane is an alkane and olefins are alkenes.

5. According to Raoult’s law, for a pure component solution the partial pressure is equals to
a) Total pressure
b) Vapour pressure
c) Atmospheric pressure
d) Mole fraction of respective phase

View Answer

Answer: b [Reason:] Generally, Raoult’s law states that, equilibrium partial pressure of a component at certain conditions equals to the product of the mole fraction and the vapour pressure. For a pure component (i.e.) mole fraction equals one. Therefore, the partial pressure equals vapour pressure.

6. According to Hendry’s law,
a) Y=(p/P)
b) Y=(p* P)
c) p=(Y/P)
d) p=(Y*P)
Where, Y=equilibrium mole fraction in vapour
pA= partial pressure
P= Total pressure

View Answer

Answer: a [Reason:] For a straight line Y=m*x, the law proved by Hendry. (i.e.) Y=(y/P) =m*x.

7. Match the following
1) Hendry’s law – a)Ideal solution
2) Dalton’s law – b)Non- Ideal solution
3) Raoult’s law -c)Sum of partial pressure

a)1- (b), 2-(c),3-(a)
b) 1-(a),2-(b),3-(c)
c)1-(c),2-(b),3-(a)
d)1-(a),2-(c),3-(b)

View Answer

Answer: a [Reason:] Dalton proved a generalized equation states that total pressure is equals to the sum of the partial pressure of the components. Raoult’s law is applicable for only ideal solution since the partial pressure is equals to the product of mole fraction and the vapour pressure.

8. Find the false statement for the better choice of absorbent.
a) Gas solubility should be high
b) Vapour pressure should be low
c) Viscosity should be high
d) Low freezing point

View Answer

Answer: b [Reason:] For a better choice of absorbent, the viscosity should be low to get the rapid absorption rates, low pressure drops in absorption tower.

9. Find the most common example for absorption.
a) Ammonia and air in solvent water
b) Ammonia and Carbon dioxide in solvent water
c) Methane and air in solvent water
d) Methane and Carbon dioxide in solvent water

View Answer

Answer: a [Reason:] Since air won’t dissolve in water the affinity of nitrogen towards the water will be more which converts ammonia into ammonium solution. But in other options the hydrocarbons easily dissolves in polar solvents.

10. Find the improper characteristic of ideal solution.
a) The average intermolecular force of attraction and repulsion are unchanged on mixing
b) Volume varies linearly with compositions
c) No evolution of heat
d) The total partial pressure varies linearly with compositions

View Answer

Answer: d [Reason:] Because the vapour pressure only varies linearly with compositions.

Machine Design MCQ Set 4

1. For the multistage counter current gas dispersed operation, which of the following equipment is better?
a) Agitated vessel
b) Sparged vessel
c) Tray tower
d) Wetted wall column

View Answer

Answer: b [Reason:] For the increased extent of mass transfer tray tower is the best equipment for gas dispersion.

2. During gas dispersion, if a chemical reaction between gas and liquid phase is needed, then the preferred equipment is
a) Agitated vessel
b) Sparged vessel
c) Tray tower
d) Wetted wall column

View Answer

Answer: a [Reason:] For a reaction to occur we need agitation for a perfect mixing between two phases.

3. The fraction of volume occupied by the gas-liquid mixture in the equipment/vessel to the volume occupied by the gas is
a) Liquid holdup
b) Gas holdup
c) Gas-liquid holdup
d) None of the mentioned

View Answer

Answer: b [Reason:] The gas holdup gives the fraction of gas in the gas-liquid mixture.

4. In a Sparged vessel of area 50 cm, the flow rate of the gas is 2 cubic meters per second then the value of superficial gas velocity in meters per second is
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: d [Reason:] Superficial gas velocity = (Volume flow rate/ cross sectional area) Superficial gas velocity= (2/0.5) =4

5. In sparged vessel of area 50 cm and a gas holdup of 3 cubic meters per cubic meters, the flow rate of the gas is 5 cubic meters per second. The value of true gas velocity in meters per second is
a) 1.11
b) 2.22
c) 3.33
d) 4.44

View Answer

Answer: c [Reason:] Superficial gas velocity= (5/0.5)= 10 True gas velocity = Superficial velocity/ gas hold up =10/3 = 3.33

6. Guess the diameter of the bubble for an air-water system in a sparged vessel with gas holdup of 0.1 and liquid flow rate of 0.15 meters per second.
a) 7.786 x10-3
b) 7.786 x10-4
c) 9.832 x10-3
d) 9.832 x10-4

View Answer

Answer: a [Reason:] For a sparged vessel, the diameter of the bubble = (2.344 x10-3)/(Relative velocity of the liquid upwards)0.67 The relative velocity of the liquid upward= liquid flow rate/ (1- gas holdup) Relative velocity = 0.15/0.9 Diameter = 7.786 x10-3

7. In a Bubble column, if the velocity of gas is low, then the bubble diameter is equals to______
a) Vessel
b) Sparger orifice
c) Volume of vessel/ interfacial area
d) None of the mentioned

View Answer

Answer: b [Reason:] In sparged vessel or bubble column, the gas is dispersed into liquid through orifice. So for a low gas velocity the diameter of the bubble will be similar to orifice diameter.

8. If the relative velocity of the gas and liquid inside bubble column of cross sectional area 0.2 meters with gas holdup of 0.736 is 3.6 meters square per second. The expected slip velocity is
a) 3.6 m/s
b) 4.89 m/s
c) 7.2 m/s
d) 9.78 m/s

View Answer

Answer: a [Reason:] The slip velocity is the relative velocity of both liquid and gas.

9. Guess the interfacial area of a bubble with a gas volume of 2.5 x10^-3 cubic meters and diameter of 0.125 cm.
a) 2 sq.m
b) 4 sq.m
c) 6 sq.m
d) 12 sq.m

View Answer

Answer: d [Reason:] As the bubble is a sphere, the surface area is (6 x volume)/diameter Interfacial area= (6 x 2.5 x10^-3)/ 0.00125= 12 sq.m

10. Find the process where agitated vessel is required.
a) Vegetable oil hydrogenation
b) Production of penicillin
c) Paper stock chlorination
d) All the mentioned

View Answer

Answer: d [Reason:] In the given examples, the chemical reaction is required for the product formation. Therefore, the agitation vessel is needed for all the examples mentioned.

11. For a better stage efficiency, must have large interfacial surface and low mass transfer co-efficient.
a) True
b) False

View Answer

Answer: b [Reason:] The turbulence intensity should be high for a better efficiency. For that the mass transfer co-efficient should be high.

12. The higher difference in pressure inside the tray tower cause
a) Flooding
b) Loading
c) Weeping
d) Dumping

View Answer

Answer: a [Reason:] If more pressure drop, the liquid won’t flow down to the adjacent trays. The liquid gets accumulated in one tray itself.

Machine Design MCQ Set 5

1. Humidification is a
a) Mass transfer operation
b) Heat transfer operation
c) Simultaneous heat and mass transfer
d) Neither mass and heat transfer operation

View Answer

Answer: c [Reason:] From the gas, heat as well as the solute components is removed.

2. In humidification the gas is ____________ in the liquid for the mass transfer to take part.
a) Soluble
b) Insoluble
c) Partially soluble
d) Inert

View Answer

Answer: b [Reason:] Generally, the purpose is to add the moisture to the gas. So, the gas won’t soluble in the liquid. Due to the heat transfer, the solute gets transferred between the phases.

3. At the gas temperature, the liquid is in equilibrium with vapour for
a) Saturated gas
b) Unsaturated gas
c) Partially saturated gas
d) None of the mentioned

View Answer

Answer: b [Reason:] The name saturated means the net mass transfer between the phases is equal which means the system is at equilibrium.

4. In an operation, the enthalpy is similar throughout the initial and final condition such operation is
a) Adiabatic
b) Non-adiabatic
c) Isothermal
d) Non-isothermal

View Answer

Answer: a [Reason:] For an adiabatic condition, there won’t be any heat addition or removal. So the enthalpy remains same.

5. For an air(A)-water vapour(B) mixture, the partial pressure of the air is 5 pa and the total pressure of the system is 15 pa. The absolute humidity in mass of air/mass of water vapour is
a) 0.805
b) 0.311
c) 0.705
d) 0.411

View Answer

Answer: a [Reason:] Absolute humidity = 5/ (10-5) x (29/18) = 0.805.

6. Mass absolute humidity is
a) Absolute humidity
b) Grosvenor humidity
c) Relative humidity
d) All the mentioned

View Answer

Answer: b [Reason:] Grosvenor proved the absolute humidity in terms of mass absolute humidity.

7. By differencing the temperature, heat added or removed is
a) Sensible heat
b) Latent heat
c) Heat of vaporization
d) None of the mentioned

View Answer

Answer: a [Reason:] Heat gain or loss is known as sensible heat.

8. For an air(A)-water vapour(B) mixture, the partial pressure of the air is 5 pa and the total pressure of the system is 15 pa. The molal absolute humidity is
a) 0.5
b) 1
c) 1.5
d) 2

View Answer

Answer: a [Reason:] Pressure of A/Total pressure- Pressure of A = 5/10 =0.5.

9. The humidity is represented in
a) Humidity chart
b) Psychometric chart
c) Psychometric chart or humidity chart
d) All the mentioned

View Answer

Answer: d [Reason:] The chart where, dry bulb and wet bulb temperature are interlinked is a humidity chart or psychometric chart.

10. De-humidification is done in
a) Adiabatic temperature
b) Adiabatic saturated temperature
c) Adiabatic unsaturated temperature
d) None of the mentioned

View Answer

Answer: b [Reason:] For de-humidification, there should be no heat addition or heat removal. For that the adiabatic saturation temperature is maintained.