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Mass Transfer

39 Questions
GATE→2026→Mass Transfer→Mass Transfer
Q1
MCQ[1 Mark]
A binary mixture of butane and butadiene is to be separated in an extractive distillation using furfural. Furfural lowers the activity of butadiene more than it does for butane. Consider the distillation sequence shown in the figure. Match the component labels in Group I with chemical species in Group II. Group I P. Component X Q. Component Y R. Component Z Group II 1. Butane 2. Butadiene 3. Furfural
Figure for Question 1
GATE→2026→Mass Transfer→Mass Transfer
Q2
NAT[1 Mark]
Consider a non-reactive binary mixture of two ideal gases A and B in an isothermal horizontal closed tube. Due to the concentration difference at the two ends of the tube, equimolal counterdiffusion occurs along the axial direction. No concentration gradients exist in the radial direction. The profile for partial pressure of component A (pAp_A) as a function of axial distance zz is shown in the figure. The partial pressure of component B (pBp_B) approaches zero at z=0.8z = 0.8 m. At a location z=z1z = z_1 the partial pressures of the components A and B are equal. The value of z1z_1 (in m) is ______ (rounded off to two decimal places).
Figure for Question 2
GATE→2026→Mass Transfer→Mass Transfer
Q3
MCQ[2 Marks]
An air and water vapor mixture at 100 kPa with a relative humidity of 20% has a dry-bulb temperature of 310 K. Assume latent heat of vaporization for water is 44 kJ mol−1^{-1} and specific heat capacity of the air and water vapor mixture is 0.035 kJ mol−1^{-1} K−1^{-1}. Which one of the following is the closest to its wet-bulb temperature (in K)?
GATE→2026→Mass Transfer→Mass Transfer
Q4
MCQ[2 Marks]
A volatile organic compound (VOC) is to be adsorbed from air onto a bed of activated carbon. The equilibrium capacity of activated carbon at the feed conditions is 0.4 grams VOC per gram of activated carbon. The column contains 4 grams of activated carbon per cm2^2 of cross-section. The feed rate into the adsorber column is 0.2 grams VOC cm−2^{-2} h−1^{-1}. Breakthrough time is defined as the time at which the concentration at the exit of the bed reaches 0.05 c0c_0. The breakthrough time is 2.1 h. The area under c/c0c/c_0 curve between the initial and breakthrough times is 0.1 h. Which one of the following is the fraction of unused bed at breakthrough?
GATE→2026→Mass Transfer→Mass Transfer
Q5
MCQ[2 Marks]
A continuous distillation column is used to separate an equimolar mixture of diethylamine (DEA) and methanol. The feed enters the column as saturated liquid at a flow rate of 30 mol s−1^{-1}; It is desired to obtain 92 mol% DEA as distillate. The rate of withdrawal of the distillate from the column is 10 mol s−1^{-1}. The equilibrium curve for the conditions in the column is given below. The latent heat of vaporization of the reboiler contents is 35 kJ mol−1^{-1}. Neglect heat loss to the surroundings and assume constant molal overflow. Which one of the following is the minimum reboiler heat duty (in kW)?
Figure for Question 5
GATE→2026→Mass Transfer→Mass Transfer
Q6
MCQ[2 Marks]
A gas stream with 2.01 mol % ammonia is to be scrubbed in a counter-current isothermal packed bed absorber using pure water to reduce its concentration to 0.01 mol %. Assume that dilute conditions apply, operating line is linear and the mass transfer coefficients are constant throughout the column. The liquid and the gas flows inside the absorber (in kmol m−2^{-2} h−1^{-1}) are 1000 and 200, respectively. The equilibrium relationship is y=0.9xy = 0.9 x. Under these conditions, the height of overall gas transfer unit (HtOGH_{tOG}) is 0.8 m and the number of overall gas transfer units (NtOGN_{tOG}) is given by the integral. Which one of the following is the minimum length of the packing (in m) necessary to achieve the desired scrubbing?
GATE→2026→Mass Transfer→Mass Transfer
Q7
NAT[2 Marks]
The flooding velocity curves for two different structured packings are shown in the figure. The ratio of mass velocities of liquid (GxG_x) to that of the gas (GyG_y) is 1.27. The density of the liquid (ρx\rho_x) is 1200 kg m−31200~\text{kg m}^{-3} and that of the gas (ρy\rho_y) is 1.2 kg m−31.2~\text{kg m}^{-3}. For both the packings, the allowable superficial vapor velocity is 60% of flooding velocity (u0,Fu_{0,F}). The ratio of allowable mass velocity of the vapor in packing P to that in packing Q is ______ (rounded off to one decimal place).
Figure for Question 7
GATE→2025→Mass Transfer→Mass Transfer
Q8
MCQ[1 Mark]
Schmidt number is defined as
GATE→2025→Mass Transfer→Mass Transfer
Q9
MCQ[1 Mark]
If kk is the mass transfer coefficient and DvD_{v} is the molecular diffusivity, which one of the following statements is NOT CORRECT with respect to mass transfer theories?
GATE→2025→Mass Transfer→Mass Transfer
Q10
NAT[1 Mark]
Oil is extracted from mustard seeds having 20 wt% oil and 80 wt% solids, using hexane as a solvent... The percentage oil recovery in hexane is ______ % (rounded off to the nearest integer).
GATE→2025→Mass Transfer→Mass Transfer
Q11
MCQ[2 Marks]
500 mg of a dry adsorbent is added to a beaker containing 100 mL solution of concentration 100 mg phenol/(L solution)... the amount of phenol adsorbed (in mg per gram of dry adsorbent) is
GATE→2025→Mass Transfer→Mass Transfer
Q12
NAT[2 Marks]
Consider moist air with absolute humidity of 0.02 (kg moisture)/(kg dry air) at 1 bar pressure. The vapour pressure equation is given. The dew temperature of the moist air is ______ °C (rounded off to the nearest integer).
GATE→2025→Mass Transfer→Mass Transfer
Q13
NAT[2 Marks]
A binary AB liquid mixture containing 30 mol% A is subjected to differential (Rayleigh) distillation... average composition of the collected distillate is ______ mol% A (rounded off to nearest integer).
GATE→2025→Mass Transfer→Mass Transfer
Q14
NAT[2 Marks]
Gas containing 0.8 mol% component A is to be scrubbed with pure water... number of transfer units, based on the gas side, NOGN_{OG} is ______ (rounded off to 1 decimal place).
GATE→2025→Mass Transfer→Mass Transfer
Q15
NAT[2 Marks]
Solute A is absorbed from a gas into water... interfacial mole fraction yiy_i equals ______ (rounded off to 3 decimal places).
GATE→2025→Mass Transfer→Mass Transfer
Q16
NAT[2 Marks]
A wet solid of 100 kg containing 30 wt% moisture is to be dried to 2 wt% moisture in a tray dryer... time required for drying is ______ h (rounded off to 1 decimal place).
GATE→2024→Mass Transfer→Mass Transfer
Q17
MCQ[1 Mark]
For the azeotropic distillation process with heavy entrainer shown in the figure, steady-state degrees of freedom equals
Figure for Question 17
GATE→2024→Mass Transfer→Mass Transfer
Q18
MCQ[1 Mark]
Consider steady uni-directional diffusion across vertical slab... molar flow rate of A in mol s−1^{-1} along x direction is
Figure for Question 18
GATE→2024→Mass Transfer→Mass Transfer
Q19
MCQ[1 Mark]
Consider a vapour-liquid mixture obeying Raoult's law. Vapour pressure of A is half that of B. Vapour phase concentrations of A and B are 3 and 6 mol m−3^{-3}. Equilibrium ratio of liquid phase concentration of A to B is
GATE→2024→Mass Transfer→Mass Transfer
Q20
MCQ[1 Mark]
Which one of the given statements is correct with reference to gas-liquid contactors for mass transfer applications?
GATE→2024→Mass Transfer→Mass Transfer
Q21
MCQ[2 Marks]
Gas stream containing 5 mol% ethanol scrubbed with water... water flow rate is twice the minimum. Mole fraction of ethanol in spent water is
GATE→2024→Mass Transfer→Mass Transfer
Q22
MCQ[2 Marks]
Sulfur dioxide gas diffuses through stagnant air-film of thickness 2 mm at 1 bar and 30 °C... steady-state flux of SO2SO_2 in mol m−2^{-2} s−1^{-1} is
GATE→2024→Mass Transfer→Mass Transfer
Q23
MCQ[2 Marks]
Simple distillation column separates binary mixture with relative volatility 2. Vapour compositions on 1st, 2nd, 3rd trays are 94, 90, 85 mol%. Reflux-to-distillate ratio is
GATE→2024→Mass Transfer→Mass Transfer
Q24
MCQ[2 Marks]
Alumina particles with initial moisture 5 kg/kg dry solid... total drying time to reduce moisture content to half initial value is h.
GATE→2024→Mass Transfer→Mass Transfer
Q25
NAT[2 Marks]
Tray-column diameter 120120 cm, downcomer area 575 cm2575 \text{ cm}^2 each (two downcomers typically). Percentage column cross-sectional area not available for vapour flow due to downcomers is %.
GATE→2023→Mass Transfer→Mass Transfer
Q26
MCQ[1 Mark]
Which one of the following is NOT an advantage of a typical spray dryer?
GATE→2023→Mass Transfer→Mass Transfer
Q27
MCQ[1 Mark]
Packed distillation column design specifications given. Column diameter (in m) is
GATE→2023→Mass Transfer→Mass Transfer
Q28
NAT[1 Mark]
Stripping column operating with V=2LV = 2L and equilibrium ye=xey_e = x_e. Minimum number of ideal stages required is.
GATE→2023→Mass Transfer→Mass Transfer
Q29
NAT[1 Mark]
Ratio of molar flux for stagnant diffusion to equimolar counter diffusion under specified mole fractions is.
GATE→2023→Mass Transfer→Mass Transfer
Q30
MCQ[2 Marks]
Water at 290 K exposed to air with 3% CO2 at 100 kPa. Henry's constant 12 MPa. Mole fraction of CO2 dissolved in water is
GATE→2023→Mass Transfer→Mass Transfer
Q31
MCQ[2 Marks]
Which one of the following represents the CORRECT effects of concentration polarization in a reverse osmosis process?
GATE→2023→Mass Transfer→Mass Transfer
Q32
NAT[2 Marks]
Partially saturated air in adiabatic saturator. Entering absolute humidity H×10−3H \times 10^{-3}, value of HH is.
GATE→2023→Mass Transfer→Mass Transfer
Q33
NAT[2 Marks]
Batch still distillation with relative volatility 4.54.5. Mole fraction of B remaining in vessel is.
GATE→2022→Mass Transfer→Mass Transfer
Q34
MCQ[1 Mark]
Consider two stationary water droplets of diameters d1d_1 and 2d12d_1. CO2 diffuses into droplets. If smaller droplet rate is W1W_1, larger droplet rate is
GATE→2022→Mass Transfer→Mass Transfer
Q35
NAT[1 Mark]
Binary A-B liquid diffusion with mole fractions 0.80.8 and 0.10.1. Quantity (NA1−NA2)NA2×100\frac{(N_{A1}-N_{A2})}{N_{A2}} \times 100 is.
GATE→2022→Mass Transfer→Mass Transfer
Q36
NAT[1 Mark]
Interphase mass transfer between immiscible liquids A and B. Mass transfer coefficient of S in A is kmol h−1m−2\text{kmol h}^{-1}\text{m}^{-2}.
GATE→2022→Mass Transfer→Mass Transfer
Q37
NAT[1 Mark]
Tray dryer solid drying calculation. Percentage moisture content of the solid at end of 5 hours is % (W/W).
GATE→2022→Mass Transfer→Mass Transfer
Q38
NAT[2 Marks]
Tray-distillation column stripping section operating line given. Reflux ratio is (rounded off to two decimal places).
GATE→2022→Mass Transfer→Mass Transfer
Q39
NAT[2 Marks]
Psychrometric calculation for wet-bulb depression of 9∘C9^\circ\text{C}. Value of 1000×Y′1000 \times Y' is.