Chemical Engineering Gate Yearwise 


Chemical Engineering Gate 2020 Questions with Answer

Ques 53 GATE 2020

An aqueous suspension at 60°C is fed to the first effect of a double effect forward feed evaporator with a mass flow rate of 1.25 kg s-1. The sum of the rates of water evaporated from the first and second effects is 1.0 kg s-1. Temperatures of the exit streams from the first and the second effects are 100 °C, and 60°C respectively. Consider the specific heat of the aqueous suspension, and the latent heat of phase change for water to be 4 kJ kg-1K-1 and 2200 kJ kg-1 respectively, over this temperature range. The steam economy (in kg per kg) is _______ (round off to 2 decimal places).


(1.80) is the correct answer.

Ques 54 GATE 2020

Two ideal cross-current stages operate to extract P from a feed containing P and Q. as shown below.

The mass flow rates of P and Q fed to Stage 1 are 1,000 kg h-1 and 10,000 kg h-1 respectively. Pure solvent (S) is injected at mass flow rates of 5,000 kg h-1 and 15,000 kg h-1 to Stages 1 and 2, respectively. The components Q and S are immiscible. The equilibrium relation is given by Y*=1.5X, where X is the mass of P per unit mass of Q in the raffinate, and Y* the mass of P per unit mass of S in the extract, which is in equilibrium with the raffinate. The mass flow rate of P (in kg h-1) in the raffinate from Stage 2 is _______ (round off to nearest integer).


(176) is the correct answer.

Ques 55 GATE 2020

Consider a vertically falling film of water over an impermeable wall. The film is in contact with a static pool of non-reactive pure gas. The gas diffuses into the water film over the entire height of the falling film. The height of the film is 1.0 m, and its thickness is 10-4 m. The velocity of water, averaged over the film thickness, is 0.01 m s-1. The gas concentration (in kg m-3), averaged over the film thickness is ‾CAy = CAi(1-e-30y) where y is the vertical position in meters measured from the top of the wall. In addition, use the following data and assumptions
• The flow is fully developed
• The width of the film is much larger than the thickness of the film, and the dissolved gas concentration is invariant over this width
• The solubility of the gas in water, CAi, is constant
• Pure water enters at y=0
• The evaporation of water is negligible
The mass transfer coefficient on the liquid side (in mm s-1), averaged over the entire height of the falling film is _______ (round off to 3 decimal places).


(0.030) is the correct answer.

Ques 56 GATE 2020

Pure gas P is being absorbed into a liquid. The dissolved P undergoes an irreversible reaction in the liquid film. The reaction is first order with respect to P. Which one of the following represents the concentration profile of P in the liquid film at steady state?

A

B

C

D


(a) is the correct answer.

Ques 57 GATE 2020

Consider a batch distillation process for an equimolar mixture of benzene and toluene at atmospheric pressure. The mole fraction of benzene in the distillate collected after 10 minutes is 0.6. The process is further continued for additional 10 minutes. The mole fraction of benzene in the total distillate collected after 20 minutes of operation is

A

less than 0.6

B

exactly equal to 0.6

C

exactly equal to 0.7

D

greater than 0.7


(a) is the correct answer.

Ques 58 GATE 2020

SO2 from air is absorbed by pure water in a counter current packed column operating at constant pressure. The compositions and the flow rates of the streams are shown in the figure.

In addition, use the following data and assumptions
• Column operates under isothermal conditions
• At the operating temperature of the column, y*=40x, where y* is the mole fraction of SO2 in the gas that is in equilibrium with water containing SO2 at a mole fraction of x
• Solution is dilute and the operating line is linear
• Negligible amount of water evaporates
The number of transfer units (NTU) for this column is

A

0.5

B

1.0

C

1.5

D

2.0


(d) is the correct answer.

Ques 59 GATE 2020

Two film theory applies for absorption of a solute from a gas mixture into a liquid solvent. The interfacial mass transfer coefficient (in mol m-2s-1) for the gas side is 0.1 and for the liquid side is 3. The equilibrium relationship is y*=2x, where x and y* are mole fractions of the solute in the liquid and gas phases, respectively. The ratio of the mass transfer resistance in the liquid film to the overall resistance is

A

0.0161

B

0.0322

C

0.0625

D

0.0645


(c) is the correct answer.

Ques 60 GATE 2020

Consider the equilibrium data for methanol-water system at 1 bar given in the figure below.

A distillation column operating at 1.0 bar is required to produce 92 mol % methanol. The feed is a saturated liquid. It is an equimolar mixture of methanol and water. The minimum reflux ratio is

A

0.33

B

0.50

C

0.54

D

1.17


(b) is the correct answer.

Ques 61 GATE 2020

A tank initially contains a gas mixture with 21 mol % oxygen and 79 mol% nitrogen. Pure nitrogen enters the tank, and a gas mixture of nitrogen and oxygen exits the tank. The molar flow rate of both the inlet and exit streams is 8 mol s-1.
In addition, use the following data and assumptions
• Assume the tank contents to be well mixed
• Assume ideal gas behavior
• The temperature and pressure inside the tank are held constant
• Molar density of the gas mixture in the tank is constant at 40 mol m-3
If the volume of the tank is 20 m3 then the time (in seconds) required for oxygen content in the tank to decrease to 1 mol % is

A

100.45

B

304.45

C

3.445

D

10


(b) is the correct answer.

Ques 62 GATE 2020

Equilibrium data for a binary mixture of E and F at two different pressures is shown in the figure.

It is desired to process a feed containing 80 mol% E and 20 mol % F, and obtain a product with a purity of 99.5 mol % E. A sequence of two distillation columns, one operating at pressure P1 and another at P2, is employed for this operation, as shown below.
Mole fraction of E in the distillate obtained from column 1 is 0.9. If the column pressures P1 and P2 are in kPa, which one of the following is correct?

A

P1=100, P2=20, and high purity E is recovered from the top of column 2

B

P1=100, P2=20, and high purity E is recovered from the bottom of column 2

C

P1=20, P2=100 and high purity E is recovered from the top of column 2

D

P1=20, P2=100 and high purity E is recovered from the bottom of column 2


(d) is the correct answer.

Ques 63 GATE 2020

In a constant-pressure cake filtration with an incompressible cake layer, volume of the filtrate (V) is measured as a function of time t. The plot of t/V versus V results in a straight line with an intercept of 104 s m-3. Area of the filter is 0.05 m2, viscosity of the filtrate is 10-3 Pa s. and the overall pressure drop across the filter is 200 kPa. The value of the filter-medium resistance (in m-1) is

A

1×109

B

1×1010

C

1×1011

D

1×1012


(c) is the correct answer.

Ques 64 GATE 2020

A rigid spherical particle undergoes free settling in a liquid of density 750 kg m-3 and viscosity 9.81×10-3 Pa s. Density of the particle is 3000 kg m-3 and the particle diameter is 2×10-4 m. Acceleration due to gravity is 9.81 m s-2. Assuming Stokes law to be valid, the terminal settling velocity (in m s-1) of the particle is

A

2×10-3

B

3×10-3

C

4×10-3

D

5×10-3


(d) is the correct answer.

Ques 65 GATE 2020

Annual capacity of a plant producing phenol is 100 metric tons. Phenol sells at INR 200 per kg, and its production cost is INR 50 per kg. The sum of annual fixed charges, overhead costs and general expenses is INR 30,00,000. Taxes are payable at 18% on gross profit. Assuming the plant runs at full capacity and that all the phenol produced is sold, the annual net profit of the plant (in INR) is

A

1,39,40,000

B

1,50,00,000

C

98,40,000

D

1,20,00,000


(c) is the correct answer.

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