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# Distillation Design MCQ’s – Mccabe Thiele Diagram-Construction

The component balance of the component A is given as

a) Fz_{F}= Dx_{D} + Wx_{w}

b) Fz_{F}= Dx_{D} – Wx_{w}

c) Fz_{F}= Dx_{D}/Wx_{w}

d) Fz_{F}= Dx_{D} *Wx_{w}

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Answer: a

Explanation: According to McCabe Thiele method material balance over is given as Fz_{F}= Dx_{D} + Wx_{w}, where F is the total feed.

If F= 200 kmol/h and Z_{F}=0.4, X_{D}=0.95, X_{W}=0.04 and R=2.0, Then D is

a) 88.1

b) 22.6

c) 79.1

d) 158.2

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Answer: c

Explanation: Using equation Fz_{F}= Dx_{D} + Wx_{w} substituting values we get D=79.1.

The very First step of McCabe method is?

a) Plot the equilibrium curve

b) Plot diagonal curve

c) Plot Operating line

d) Plot stripping line

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Answer: a

Explanation: Firstly we plot the Equilibrium diagram from the given equilibrium data, then the diagonal curve and then plot the operating line.

Calculate Boil up? If vapor flow and bottom withdrawal are 237.3 and 120.9 respectively

a) 1.5

b) 2.9

c) 2.111

d) 1.963

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Answer: d

Explanation: As boil up is ratio of vapor flow and bottom withdrawal then 237.3/120.9 = 1.963.

If ZF¬=0.58 and also feed contains 35% mole of the liquid, then intercept of y axis is

a) 0.892

b) 0.205

c) 0.707

d) Can’t be calculated

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Answer: a

Explanation: As – (Z_{F}/q-1) using values -0.58/ (0.35-1) = 0.892.

If Z_{F}=0.6 and also feed contains 72% mole of the liquid, then intercept of x axis is

a) 0.744

b) 0.899

c) 0.833

d) 1.2

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Answer: c

Explanation: As (ZF/q) using values 0.6/ (0.72) = 0.833.

Calculate minimum reflux? If intercept is 0.56 and X_{D}= 0.96

a) 0.174

b) 0.125

c) 0.21

d) 0.28

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Answer: a

Explanation: As 0.56=X_{D}/ (R_{M}+1) = 0.96/ (R_{M}+1) M= 0.174

Slope of rectifying line is given by

a) R/X_{D}

b) R/(R+1)

c) F/ (D+W)

d) R/(R+1)

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Answer: b

Explanation: The rectifying line slope is always given as ratio of Reflux ratio plus unity i.e. R/(R+1), While R/X_{D} gives us the reflux to liquid ratio for the operation.

If x_{D}=0.95, x_{W}= 0.04 and α=2.5. Find total trays?

a) 7

b) 6.7

c) 7.7

d) 6

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Answer: b

Explanation: Using Fenske’s equation total number of trays to be calculate are 5.7 as N_{m} + 1 then 5.7+1 = 6.7 which is the final answer.

A Pinch point may occur at intersection of feed line and

a) Stream line

b) Stripping line

c) Rectifying line

d) Equilibrium line

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Answer: d

Explanation: Pinch point always occurs at intersection of feed line and equilibrium line, while plot of x and y are called as the Equilibrium line.