Chemical Engineering Interview Questions on MASS TRANSFER OPERATIONS

1.            What is meant by differential distillation?

Ans: Click Here
2.            Draw a equilibrium diagram and boiling point diagram for an azeotropic binary system.
3.            Raoult's law applies to the __________ and Henry's law applies to the _________
4.            What is relative volatility?
5.            What is Murphree tray efficiency?
6.            What is meant by constant molal overflow?
7.            Define the term ''minimum reflux ratio''.
8.            Ponchon-Savarit method analyses the fractionating equipment based on _____________
9.            What is stripping factor?
10.         Draw a neat sketch of packed absorption tower.
11.         Write down the properties of a good packing for an absorption tower.
12.         Write few industrial application of absorption.
13.         What is a plait point?
14.         What is selectivity? Selectivity of solvent used in extraction should be ____________
15.         What are the factors which affect a leaching operation?
16.         Explain the terms extraction and leaching.
17.         What are the desirable properties of an industrial adsorption?
18.         What is meant by a break through curve for adsorption?
19.         What are the various types of dialysis?
20.         Write the principle of Ion-exchange.
21.         Differentiate between flash distillation, differential distillation and rectification
22.         What is distillation?
23.         What are the limitations of distillation?
24.         Derive the expression y = αx/(1+( α-1)x)
25.         Explain Flash Vaporization.
26.         Explain the term total reflux.
27.         What is the use of open steam and how to calculate the number of stages in case of open steam
28.         Define molecular distillation.
29.         What is the use of entrainer in Azeotropic distillation?
30.         What is meant by desorption?
31.         Define the term Minimum Reflux ratio.
32.         Give the Vont Hoffs law of mobile equilibrium.
33.         Define flooding and loading in an absorber.
34.         Define the term leaching and extraction.
35.         What is distribution law?
36.         Explain the use of triangular graph for extraction.
37.         What are the different types of adsorption?
38.         Explain the process of Ion exchange.
39.         Define selectivity and distribution coefficient.
40.         Define Thermal and sweep diffusion.
41.         What are the various types of dialysis?
42.         What are the advantages of distillation over absorption?
43.         Define the term relative volatility
44.         State Henry's law
45.         What is Murphree tray efficiency?
46.         What is meant by equilibrium distillation?
47.         What is absorption factor?
48.         What is molecular distillation?
49.         Sketch the operating line and equilibrium curve for an absorber and stripper
50.         What is meant by minimum liquid gas ratio?
51.         What is plait point?
52.         Explain percolation method of leaching?
53.         Define distribution coefficient and state its importance
54.         What is electrodialysis?
55.         What are the properties of solvent for extraction?
56.         What is ion retardation?
57.         Mention few industrial adsorbents
58.         What is adsorption hysteresis?
59.         Write the principle of ion-exchange
60.         What is meant by constant molal over flow?
61.         What is the role of Raoult's law in distillation?
62.         Write short notes on:                                                                                              (i) Azeotropic distillation (ii) Extractive distillation (iii) Rayleigh's equation
63.         The HTU and NTU concepts in packed columns.
64.         Adiabatic saturation temperature.
65.         Miers theory of crystallization
66.         Spray drying
67.         Dehumidification process
68.         Induced draft cooling tower
69.         Vacuum crystallizer
70.         Two film theory
71.         Cooling towers
72.         Reynolds analogy
73.         Wet-bulb temperature
74.         HTU and HETP
75.         Over all and individual phase mass transfer coefficients
76.         Psychrometric chart
77.         Lewis number and its significance
78.         Effect of gas velocity on batch drying characteristics
79.         Drying of food grains
80.         Critical, bound and unbound moisture contents
81.         Analogy between momentum, heat and mass transfer
82.         Fluidized bed dryers
83.         Air-conditioning equipments
84.         Swenson-Walker crystallizer
85.         Schmidt number and its significance
86.         J - factors
87.         Estimation of diffusivities
88.         Induced draft cooling towers
89.         Rotary dryers
90.         Molecular and Eddy diffusion
91.         Nucleation
92.         Explain the term "FLUX"
93.         What is meant by molecular diffusion and eddy diffusion?
94.         Define the term diffusivity
95.         Give the Wilke-Chang equation and explain the terms involved in it.
96.         Why various theories of mass transfer have been proposed?
97.         Explain the term stage and stage efficiency
98.         What is meant by absorption factor?
99.         Explain the theory of humidification
100.       What is meant by wet bulb temperature approach?
101.       What is the principle of 'recirculating liquid gas humidifier'?
102.       Define Dew point
103.       Define the term "Bound moisture"
104.       Explain the effect of temperature and mass flow rate of air on the constant drying rate, NC.
105.       What is meant by holdup in a rotary dryer?
106.       Which type of drier is used in the manufacture of (a) tablets (b) Paraffin wax?
107.       What is crystallization?
108.       State McCabe's L law of crystal growth
109.       What is the purpose of agitator in the crystallizer?
110.       Give examples of batch crystallizer and continuous crystallizer

Diffusion and Mass Transfer Coefficients: 
111.       Define the terms a) diffusion b) mass diffusivity c) eddy diffusion
112.       What is the unit for mass diffusivity?
113.       Draw a graph showing concentration gradient for equimolal diffusion
114.       What is Sherwood number and give its significance?
115.       Give the relationship between mass transfer coefficient and diffusivity
116.       What is the effect of pressure and temperature on the diffusion coefficient in gases?
117.       Define 'Absorption factor'
118.       Define: a) humidity b) percentage humidity and c) relative humidity
119.       How the cooling effect in a cooling tower can be increased?
120.       Define a) Dew point and b) bubble Point
121.       Define the term Equilibrium moisture and free moisture content of solid
122.       What is freeze-drying?
123.       Which drier is suitable for handling fragile crystals?
124.       During drying operation, critical moisture content varies with _________.
125.       Write down the sequence of stages in the evolution of a crystal
126.       Write down the three methods used to produce super-saturation
127.       What is magma?
128.       What is the purpose of agitator in a crystallizer
129.       Explain. What do you understand by jD and jH factors?
130.       Write short notes on following mass transfer theories                                                        (i) Film theory (ii) Surface renewal theory         (iii) Penetration theory 

131.       What do you understand by 'liquid film controlling' in gas absorption? Suggest methods of increasing the rate of transfer for this condition.
132.       Derive Kremser-Brown-Souders equation for the calculation of number of theoretical stages for absorption in a stagewise contact tower.
133.       Compare the performance of bubble-cap column, sieve-tray column and packed bed column. Discuss in detail the operation of any column.
134.       When are the concepts of HETP and HTU used? What is the difference between the two? Drawing an equilibrium diagram, indicate clearly the two concepts.
135.       Illustrate the significance of operating line and equilibrium line for a steady state counter-current process.
136.       Discuss briefly the 'flooding' and 'loading' conditions in a packed tower stating the factors which influence them.
137.       Discuss briefly the important design and operational aspects of
1.            Bubble cap column and        2.          Sieve tray tower.
138.       Define absorption factor. Indicate its physical significance and uses in the design of absorbers.
139.       Discuss the use of Murphree efficiency for the design of an absorber.
140.       Discuss briefly how the minimum solvent requirement in counter-current gas absorption may be determined.
141.       What is flooding velocity? What role does it play in the design of absorption column?
142.       Specify the important properties a packing material should possess for being used in mass transfer equipment. Name a few packing materials.
143.       How do you express the efficiency of an absorption plate and an absorption column? Give an idea of an ideal plate.
144.       Indicate the methods used for the design of absorption towers for absorption with chemical reaction. Explain the type of data needed in the design and how this data is obtained.

145.       Compare the several adsorption isotherms you know of and discuss their importance in adsorption steps in a chemical engineering operation.
146.       Draw the break-through curve for an adiabatic batch adsorption bed. Discuss the main features.
147.       What are the characteristics to be possessed by industrial adsorbents? What are the commonly used adsorbents?

148.       Discuss the factors which govern the selection of solvents to be used for liquid-liquid extractions.
149.       Write in short the procedure to determine the number of theoretical stages for counter-current multistage extraction.

150.       Discuss briefly the typical equilibrium diagrams in leaching
151.       Explain the graphical method of determining the number of theoretical stages in a multistage counter-current leaching.

152.       Explain entrainment, foaming, coning and limiting vapor velocity in distillation.
153.       What is flash vaporization? Obtain relationship for liquid to vapor product ratio in terms of enthalpies of different streams.
154.       Derive Raleigh’s equation for differential distillation.
155.       Why the reflux is used and how does it affect the size of the distillation tower?
156.       Explain, with necessary equations, the utility of Ponchon-Savarit method of determining the number of ideal plates in a fractionating column. How is the McCabe-Thiele method a simplification of this?
157.       When is distillation by steam used? Explain with necessary expressions, the effect of using vacuum in steam consumption in such an operation.
158.       Discuss the principles, operation and industrial applications of the following giving examples.                                                                                                          1) Azeotropic distillation         2) Extractive distillation  3) Molecular distillation
159.       Indicate how the use of the enthalpy-composition diagram and McCabe-Thiele diagram could be utilized for the design of distillation columns. Specify the application of each method. Explain by means of both the methods to determine:
1.        minimum reflux 2)    the number of plates at total reflux and the
2.        Location of the correct feed plate in the fractionation of liquid mixture in a bubble plate column using open steam.
160.       State with reasons whether the following statements are correct or not, give appropriate equations wherever possible. 
1.        Raoult's law applies to the solute and Henry's law applies to the solvent.
2.        In a rectification column, the heat requirement in the re-boiler gets fixed if the reflux ratio is fixed.
                       3.        Murphree plate efficiency can be above 100%.

Interview Questions on Chemical Reaction Engineering Click Here

Interview Questions on Mass Transfer Operations Click Here 

Interview Questions on Fluid Mechanics Click Here 

Interview Questions on Transport Phenomena Click Here 

Interview Questions on Industrial catalysis Click Here

For More Interview questions Click Here


  1. these all question of mass transfer OPERATIONS are really useful.

  2. Thanks for the post!
    Rufouz hitek engineers pvt ltd are one of the most noticeable industry of manufacturing
    and suppliers of a wide range of industrial machineries which used all across the globe.
    Industrial equipment suppliers in mumbai