Engineering Questions with Answers - Multiple Choice Questions

# Separation Processes MCQ’s – McCabe-Thiele Graphical Method for Trayed Towers

1 - Question

What is the goal of distillation?
a) To produce a distillate rich in light key and the bottoms product rich in high key
b) To produce a distillate rich in high key and the bottoms product rich in light key
c) To produce a distillate rich in light key and the bottoms product rich in light key
d) To produce a distillate rich in high key and the bottoms product rich in high key
Explanation: The goal of distillation is to produce a distillate rich in light key and the bottoms product rich in high key.

2 - Question

What is meant by light key (LK)?
a) A feed that contains less volatile components
b) A feed that has less mass
c) A feed that has higher concentration of less molecular weight solute
d) A feed that contains more volatile components
Explanation: Light key is the feed that contains more volatile components.

3 - Question

What is meant by high key (HK)?
a) A feed that contains less volatile components
b) A feed that has less mass
c) A feed that has higher concentration of less molecular weight solute
d) A feed that contains more volatile components
Explanation: High key is the feed that contains less volatile components.

4 - Question

If LK=1 and HK=2, what is the formula for α 1,2 ?
a) α 1,2 =K1/K2
b) α 1,2 =K1*K2
c) α 1,2 =K1-K2
d) α 1,2 =K1+K2
Explanation: To find out whether the separation is possible or not α 1,2 values are used whose formula is α 1,2 =K1/K2.

5 - Question

For what value of α1,2 ,the separation cannot be achieved?
a) 0.8
b) 1.2
c) 1.3
d) 1.8
Explanation: For α1,2 = 0.8, the separation cannot be achieved since its value has to be greater than 1.Thus by further increasing pressure, separation cannot be achieved.

6 - Question

What is the formula for distillation rate according to mcCabe-thiele’s method?
a) D= F(z F – x B )/(x D + x B )
b) D= F(z F – x B)/(x D /x B )
c) D= F(z F – x D )/(x D – x B )
d) D= F(z F – x B )/(x D – x B )
Explanation: D= F(z F – x B )/(x D – x B ) is the correct equation where D is the distillation rate, F is the total feed rate, z F is the mole fraction of LK in feed, x D , x B are mole fractions of LK in distillate and bottom.

7 - Question

What is the distillation rate if feed rate is 4moles/s and mole fraction of LK in feed is 0.7, and mole fraction of LK in distillate and bottom is 0.5, 0.4?
a) 8moles/s
b) 12moles/s
c) 16moles/s
d) 20moles/s
Explanation: Since D= F(z F – x B )/(x D – x B ), D=4*(0.7-0.4)(0.5- 0.4)=12.

8 - Question

What is the distillation rate if feed rate is 20moles/s and mole fraction of LK in feed is 0.8, and mole fraction of LK in distillate and bottom is 0.5, 0.4?
a) 80moles/s
b) 12moles/s
c) 16moles/s
d) 20moles/s
Explanation: Since D= F(z F – x B )/(x D – x B ), D=20*(0.8-0.4)(0.5- 0.4)=80.

9 - Question

What is the distillation rate if feed rate is 9moles/s and mole fraction of LK in feed is 0.7, and mole fraction of LK in distillate and bottom is 0.5, 0.3?
a) 45moles/s
b) 16moles/s
c) 18moles/s
d) 20moles/s
Explanation: Since D= F(z F – x B )/(x D – x B ), D=9*(0.7-0.3)(0.5- 0.3)=18.

10 - Question

What is the distillation rate if feed rate is 31moles/s and mole fraction of LK in feed is 0.9, and mole fraction of LK in distillate and bottom is 0.6, 0.4?
a) 23moles/s
b) 26moles/s
c) 28moles/s
d) 31moles/s