# Mass Transfer Questions and Answers – Material Balance Concepts-Cocurrent

This set of Mass Transfer Questions & Answers for freshers focuses on “Material Balance Concepts-Cocurrent”.

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

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

2. Look out the figure below

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
Explanation: 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

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
Explanation:
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.
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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
Explanation: -Ls/Gs= 0.6-0.4/(0.45-0.25)
= 1.

5. Assume an ideal solution with pure component A, has a 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
Explanation: 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.
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6. The figure given below is a single stage ideal co- current process of solute transfer from liquid to gas phases.

a) True
b) False
View Answer

Answer: a
Explanation: 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

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
Explanation: In the diagram, the operating line is a curve, only if the concentration is expressed in mole fraction the operating line is a curve.
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8. The operating line will be straight if its concentrations are represented in mole ratio.
a) True
b) False
View Answer

Answer: a
Explanation: 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 a straight operating line
a) True
b) False
View Answer

Answer: a
Explanation: 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.
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10. Name of the line PR and QT

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
Explanation: The distance from the Interphase is known as Driving force line.

Sanfoundry Global Education & Learning Series – Mass Transfer.

To practice all areas of Mass Transfer for freshers, here is complete set of 1000+ Multiple Choice Questions and Answers

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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