Mass Transfer Questions for entrance exams on “Reflux Ratio Concept (Minimum, Maximun & Optimum)”.
1. If the reflux is total, minimum stages are used.
a) True
b) False
Answer: a
Clarification: For total reflux no distillate formation; all the condensed vapour are sent back to fractionator.
2. At Total reflux
a) Residue is nil
b) Distillate is nil
c) Reflux is nil
d) All of the mentioned
Answer: b
Clarification: Total reflux there condensed vapours are sent back to the column itself.
3. Reflux ratio is infinity at
a) Total reflux
b) Minimum reflux
c) Part reflux
d) None of the mentioned
Answer: a
Clarification: Reflux ratio becomes infinity at distillate is equals to zero. Since reflux ratio = Reflux/distillate
At distillate = 0; Reflux ratio= infinity.
4. Estimate the condenser requirement for total reflux.
a) Small condenser
b) Medium condenser
c) Large condenser
d) Partial condenser
Answer: c
Clarification: Since if the large condenser are used, vapour gets condensed and becomes reflux where distillate is zero.
5. For minimum reflux ratio the number of trays becomes infinite.
a) True
b) False
Answer: a
Clarification: For minimum reflux ratio, all the condensed vapour becomes distillate; no reflux. So it requires infinite number of trays.
6. For a minimum reflux ratio ________ condenser or reboiler loads are used.
a) Less
b) More
c) Infinity
d) Partial
Answer: a
Clarification: Since for minimum reflux ratio no reflux is produced, it’s enough to use minimum load condenser or reboiler.
7. Find the representation X.
a) Partial condenser
b) Total condenser
c) Reboiler
d) None of the mentioned
Answer: b
Clarification: All the condensed vapours are refluxed (no distillate).
8. For finding the exact number of trays the reflux ratio should be between minimum and infinity.
a) True
b) False
Answer: a
Clarification: The minimum trays cannot be determined; also infinite trays are impossible; so the trays should be minimum and infinity.
9. The reflux ratio increases by increasing the reflux and decreasing the distillate.
a) True
b) False
Answer: a
Clarification: Reflux ratio= reflux/distillate.
10. Find the co-relation of the representation.
a) Maximum reflux ratio
b) Optimum reflux ratio
c) Minimum reflux ratio
d) None of the mentioned
Answer: c
Clarification: Since there is no reflux, all the condensed vapours are distillate. Then it represents minimum reflux ratio.
Mass Transfer for entrance exams,