This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Distillation of Binary Mixtures”.
1. What is distillation reflux ratio?
a) Ratio between the boil up rate and the take-off rate
b) Product of boil up rate and the take-off rate
c) Sum of boil up rate and the take-off rate
d) Ratio between the take-off rateand boil up rate
View Answer
Explanation: The Reflux ratio is the ratio between boil up rate and take-off rate. It is the relation between the amount of reflux that goes back down the distillation column and the amount of reflux that is collected in the collection flask.
2. Are these statements about the binary distillation true?
Statement 1: Binary distillation is a common separation technique used in chemical process industries.
Statement 2: During this process, the mixture of components is separated by their phases.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer
Explanation: Binary distillation is a method used in chemical process industries to purify mixtures into their two separate components. In this process, the component mixture is separated by their phases. The lighter species is vaporized and leaves the column through the distillate. Whereas heavier species is in liquid form and collected at bottom.
3. What factors affect distillation?
a) Solubility
b) Relative volatility
c) Surface area
d) Solubility, relative volatility and surface area
View Answer
Explanation: Distillation is affected by activity coefficient, solubility, relative volatility, maximum achievable concentration and surface area.
4. Which of the following is explained by using McCabe-Thiele plot?
a) Distillation
b) Crystallization
c) Molecular separation
d) Freezing
View Answer
Explanation: The McCabe-Thiele plot is a basic tool to assist distillation. It is a method to calculate the number of theoretical trays required for the distillation process of a binary mixture.
5. What is Q in McCabe Thiele method?
a) Mole fraction of liquid in the feed
b) Concentration
c) Viscosity
d) Temperature
View Answer
Explanation: The parameter q is known to be mole fraction of liquid in the feed and the typical McCabe-Thiele diagram uses a q-line which represents partially vaporized feed.
6. Can Murphree efficiency be greater than 100?
a) True
b) False
View Answer
Explanation: Murphee efficiency is the ratio of the actual change in vapor composition when the vapor passes through the liquid on a tray to the composition change of the vapor if it were in vapor liquid at equilibrium with the tray liquid.
7. What are the limitations of McCabe Thiele method?
a) Cannot analyze mixtures containing more than 2 components
b) Cannot analyze freeze dry product
c) Cannot analyze mixtures at high temperature
d) Cannot analyze mixtures at low temperature
View Answer
Explanation: The main drawback of the McCabe-Thiele Method is that it is not very beneficial for analyzing the distillation of mixtures comprising more than 2 components. However, the method is still valuable as a teaching tool and a conceptual tool.
8. What does high reflux ratio mean?
a) Higher purity of the distillate
b) Lower purity of the distillate
c) Collection rate will be higher
d) Does not depend on purity and collection rate
View Answer
Explanation: The higher the reflux ratios, more contact of vapor/liquid occur in the distillation column. Therefore a higher reflux ratio means higher purity of the distillate and also means that the distillate will have slower collection rate.
9. Which of the following trays are used in distillation?
a) Bubble cap tray, sieve deck tray
b) Bubble cap tray, pore sieve tray
c) Sieve deck tray, pore sieve tray
d) Bubble cap tray, multi-flow tray
View Answer
Explanation: There are five major types of tray column that are used in distillation process. They are bubble cap tray, sieve deck tray, dual flow tray, valve tray and baffle tray.
10. Which of the following shape represents the number of theoretical stages in McCabe-Thiele plot?
a) Vertical line
b) Circle
c) Triangle
d) Square
View Answer
Explanation: In the McCabe-Thiele plot, the number of theoretical stages required for a given separation is represented by the number of triangles that can be drawn between operating lines and equilibrium curve. The reboiler is represented as the last triangle on the plot.
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