GATE CH Mass Transfer PYQs & Answers — Page 2

Questions 11–20 of 77. Imported answers require independent review unless marked reviewed.

500 mg of a dry adsorbent is added to a beaker containing 100 mL solution of concentration 100 mg phenol/(L solution). The adsorbent is separated out after 5 h of rigorous mixing. If the residual concentration in the solution after separating the adsorbent is 30 mg phenol/(L solution), the amount of phenol adsorbed (in mg per gram of dry adsorbent) is

Your answerChoose one option.

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Consider moist air with absolute humidity of 0.02 (kg moisture)/(kg dry air) at 1 bar pressure. The vapour pressure of water is given by the equation

where

is in bar and

is in K. The molecular weight of water and dry air are 18 kg/kmol and 29 kg/kmol, respectively. The dew temperature of the moist air is ____ °C (rounded off to the nearest integer).

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A binary

liquid mixture containing 30 mol%

is subjected to differential (Rayleigh) distillation at atmospheric pressure in order to recover 60 mol%

in the distillate. Assuming a constant relative volatility

, the average composition of the collected distillate is ____ mol%

(rounded off to nearest integer).

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Gas containing 0.8 mol% component

is to be scrubbed with pure water in a packed bed column to reduce the concentration of

to 0.1 mol% in the exit gas. The inlet gas and water flow rates are 0.1 kmol/s and 3.0 kmol/s, respectively.

For the dilute system, both the operating and equilibrium curves are considered linear. If the slope of the equilibrium line is 24, the number of transfer units, based on the gas side,

is ____ (rounded off to 1 decimal place).

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Solute

is absorbed from a gas into water in a packed bed operating at steady state. The absorber operating pressure and temperature are 1 atm and 300 K, respectively. At the gas-liquid interface

where

and

are the interfacial gas and liquid mole fractions of

, respectively. At a particular location in the absorber, the mole fractions of

in the bulk gas and in the bulk water are 0.02 and 0.002, respectively. If the ratio of the local individual mass transfer coefficients for the transport of

on the gas-side (

) to that on the water-side (

, then

equals ____ (rounded off to 3 decimal places).

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Components

and

form an azeotrope. The saturation vapour pressures of

and

at the boiling point are 87 kPa and 72.7 kPa, respectively. The azeotrope composition is ____ mol%

(rounded off to the nearest integer).

GIVEN:

where

and

are the liquid phase mole fraction and activity coefficient of component

, respectively.

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A wet solid of 100 kg containing 30 wt% moisture is to be dried to 2 wt% moisture in a tray dryer. The critical moisture content is 10 wt% and the equilibrium moisture content is 1 wt%. The drying rate during the constant rate period is 10 kg/(h m

). The drying curve in the falling rate period is linear. If the drying area is 5 m

, the time required for drying is ____ h (rounded off to 1 decimal place).

Note: All the moisture values given are on dry-solid basis.

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Consider the steady, uni-directional diffusion of a binary mixture of A and B across a vertical slab of dimensions 0.2 m × 0.1 m × 0.02 m as shown in the figure. The total molar concentration of A and B is constant at 100 mol m

. The mole fraction of A on the left and right faces of the slab are maintained at 0.8 and 0.2, respectively. If the binary diffusion coefficient

, the molar flow rate of A in mol s

, along the horizontal

direction is

Diagram for Chemical Engineering question 17

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Consider a vapour-liquid mixture of components A and B that obeys Raoult’s law. The vapour pressure of A is half that of B. The vapour phase concentrations of A and B are 3 mol m

and 6 mol m

, respectively. At equilibrium, the ratio of the liquid phase concentration of A to that of B is

Your answerChoose one option.

1.0

0.5

2.0

1.5

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Consider the control structure for the overhead section of a distillation column shown in the figure. The composition controller (CC) controls the heavy key impurity in the distillate by adjusting the setpoint of the reflux flow controller in a cascade arrangement. The sign of the controller gain for the pressure controller (PC) and that for the composition controller (CC) are, respectively,

Diagram for Chemical Engineering question 23

Your answerChoose one option.

negative, negative

negative, positive

positive, positive

positive, negative

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GATE CH Mass Transfer PYQs

Question 40

Question 47

Question 54

Question 55

Question 56

Question 57

Question 65

Question 17

Question 18

Question 23