Mass Transfer Questions & Answers for freshers 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
Answer: a
Clarification: 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
Answer: a
Clarification: 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
Answer: b
Clarification:
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
Answer: a
Clarification: -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
Answer: a
Clarification: 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.
a) True
b) False
Answer: a
Clarification: 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
Answer: c
Clarification: 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
Answer: a
Clarification: 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
Answer: a
Clarification: 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
If X, Y – are represented in mole ratio
a) Interface line
b) Driving force line
c) Parallel line
d) Normal line