A
fiberboard sheet (1.5 m × 2.0 m × 15 mm) is being dried by suspending it
horizontally in a current of hot, dry air. The edges are insulated so that
drying takes place only from the top and bottom surfaces. The wet sheet
weighing 16 kg with initial moisture content of 60% loses moisture at a
constant rate of 1.25 × 10-5 kg m-2 s-1 until
the moisture content falls to 30%. All moisture contents are on dry basis. The
time required for drying during constant rate period (in hour) is
_________________ (rounded off to third decimal place).
GATE
2018
Answer: 11.11
The composition
of vapour entering a tray in a distillation column is 0.47. The average
composition of the vapour leaving the tray is 0.53. The equilibrium composition
of the vapour corresponding to the liquid leaving this tray is 0.52. All the
compositions are expressed in mole fraction of the more volatile component.
The Murphree
efficiency based on the vapour phase, rounded to the nearest integer, is ______
%.
GATE
2017
Answer: 120
Which of the
following conditions are valid at the plait point?
P) Density
difference between the extract and raffinate phases is zero
Q) Interfacial
tension between the extract and raffinate phases is zero
R) Composition
difference between the extract and raffinate phases is zero
(A) P
and Q only
(B) Q
and R only
(C) P
and R only
(D) P,
Q and R
GATE 2017
Answer: (D)
In a batch
adsorption process, 5 g of fresh adsorbent is used to treat liter of an aqueous
phenol solution. The initial phenol concentration is 100 mg/liter. The
equilibrium relation is given by
q* = 1.3C
Where, q* is the
amount of phenol adsorbed In mg of phenol per gram of adsorbent and C is the
concentration of phenol in mg/liter in the aqueous solution.
When equilibrium
is attained between the adsorbent and the solution, the concentration of phenol
in the solution, rounded to 1 decimal place, is _____________ mg/liter.
GATE
2017
Answer: 13.33
Consider steady
state mass transfer of a solute A from a gas phase to a liquid phase. The gas
phase bulk and interface mole fractions are yA,G and yA,i,
respectively. The liquid phase bulk and interface mole fractions are xA,L
and xA,i, respectively. The ratio (xA,i – xA,L)/(yA,G
– yA,i) is very close to zero.
This implies
that mass transfer resistance is
(A)
Negligible in the gas phase only
(B)
Negligible in the liquid phase only
(C)
Negligible in both the phases
(D)
Considerable in both the phases
GATE 2017
Answer: (B)
The vapour phase
composition and relative volatilities (with respect to n-propane) on an ideal
tray of a distillation column are
|
Component |
Methane |
Ethane |
n-Propane |
|
Mole
fraction in vapour |
0.12 |
0.28 |
0.60 |
|
Relative
volatility |
10 |
4 |
1 |
The mole fraction
of n-propane in the liquid phase, rounded to 2 decimal places, is ______.
GATE
2017
Answer: 0.9
The Sherwood
number (ShL) correlation for laminar flow over a flat plate of
length L is given by
Where, ReL
and Sc represent Reynolds number and Schmidt number, respectively.
This
correlation, expressed in the form of Chilton-Colburn jD factor, is
GATE
2017
Answer: (B)
Ina counter
current stripping operation using pure steam, the mole ratio of a solute in the
liquid stream is reduced from 0.25 to 0.05. The liquid feed flow rate, on a
solute-free basis, is 3 mol/s. The equilibrium line for the system is given in
the figure below.
The MINIMUM flow
rate of pure steam for this process, rounded to 1 decimal place, is _____
mol/s.
GATE
2017
Answer: 4
A
binary distillation column is to be designed using McCabe Thiele method. The
distillate contains 90 mol% of the more volatile component. The point of
intersection of the q-line with the equilibrium curve is (0.5, 0.7). The
minimum reflux ratio (rounded off to the first decimal place) for this
operation is _______.
GATE 2016
Answer: 1
Solute
C is extracted in a batch process from its homogenous solution of A and C,
using solvent B. The combined composition of the feed and the extracting
solvent is shown in the figure below as point M, along with the tie line
passing through it. The ends of the tie line are on the equilibrium curve.
What is the selectivity for C?
(A) 3.5
(B) 7
(C) 10.5
(D) 21
GATE
2016
Answer: (C)
At 30⁰C, the amounts of acetone adsorbed at partially pressures of
10 and 100 mmHg are 0.1 and 0.4 kg acetone/kg activated carbon, respectively.
Assume Langmuir isotherm describes the adsorption of acetone on activated
carbon. What is the amount of acetone adsorbed (in kg per kg of activated
carbon) at a partial pressure of 50 mm Hg and 30⁰C?
(A) 0.23
(B) 0.25
(C) 0.30
(D) 0.35
GATE
2016
Answer: (C)
Consider the following two cases for a
binary mixture of ideal gases A and B under steady state conditions. In Case 1,
the diffusion of A occurs through non-diffusing B. In Case 2, equimolal counter
diffusion of A and B occurs. In both the cases, the total pressure is 100 kPa
and the partial pressures of A at two points separated by a distance of 10 mm
are 10 kPa and 5 kPa. Assume that the Fick’s first law of diffusion is
applicable. What is the ratio of molar flux of A in Case 1 to that in Case 2?
(A) 0.58
(B) 1.08
(C) 1.58
(D) 2.18
GATE
2016
Answer: (B)
A binary liquid mixture of benzene
and toluene contains 20 mol% of benzene. At 350 K the vapour pressures of pure
benzene and pure toluene are 92 kPa and 35 kPa, respectively. The mixture
follows Raoult’s law. The equilibrium vapour phase mole fraction (rounded off
to the second decimal place) of benzene in contact with this liquid mixture at
350 K is _______.
GATE
2016
Answer: 0.4
Match the dimensionless numbers in Group-1
with the ratios in Group-2.
|
|
Group-1 |
|
Group-2 |
|
P |
Biot
number |
I |
Buoyancy force/viscous
force |
|
Q |
Schmidt
number |
II |
Inter thermal
resistance of a solid/boundary layer thermal resistance |
|
R |
Grashof
number |
III |
Momentum diffusivity
/mass diffusivity |
(A)
P-II, Q-I, R-III
(B)
P-I, Q-III, R-II
(C)
P-III, Q-I, R-II
(D)
P-II, Q-III, R-I
GATE
2016
Answer: ()
For what value of Lewis number, the
wet-bulb temperature and adiabatic saturation temperature are nearly equal?
(A)
0.33
(B)
0.5
(C)
1
(D)
2
GATE 2016
Answer: (C)
A multi-stage,
counter-current liquid-liquid extractor is used to separate solute C from a
binary mixture (F) of a and C using solvent B. Pure solvent b is recovered from
the raffinate R by distillation, as shown in the schematic diagram below.
Locations
of different mixtures for this process are indicated on the triangular diagram
below. P is the solvent-free raffinate, E is the extract, F is the feed and Δ
is the difference point from which the mass balance lines originate. The line
PB intersects the bimodal curve at U and T. The lines PΔ and FB intersect the
bimodal at V and W respectively.
The raffinate
coming out of the extractor is represented in the diagram by the point:
(A)
T
(B)
U
(C)
V
(D)
W
GATE
2015
Answer: (B)
A binary feed
consisting of 25 mol% liquid and 75 mol% vapour is separated in a staged
distillation column. The mole fraction of the more volatile component in the
distillate product is 0.95. The molar flow rate of distillate is 50% of the
feed flow rate and the McCabe-Thiele method can be used to analyze the column.
The q-line intersects the operating line of the enriching section at (0.35,
0.5) on the x - y diagram. The slope of the stripping section operating line
(up to one decimal place) is __________.
GATE
2015
Answer: 1.4
Consider a
steady state mass transfer process between well-mixed liquid and vapour phases
of a binary mixture comprising of components A and B. The mole fractions of
component A in the bulk liquid (xA) and bulk vapour (yA)
phases are 0.36 and 0.16, respectively. The mass transfer coefficients for
component A in liquid and vapour phases are 0.1 mol/(m2.s) and 0.05
mol/(m2.s), respectively. The vapour-liquid equilibrium can be
approximated as yA* = 2xA, for xA
less than 0.4. The mole fraction of A in the liquid at the interface (up to two
decimal places) is _____________.
GATE 2015
Answer: 0.22
Adsorption on
activated carbon is to be used for reducing phenol concentration in wastewater
from 0.04 mol/l to 0.008 mol/l. The adsorption isotherm at the operating
temperature can be expressed as q = 0.025 C1/3; where q is the
phenol concentration in solid (mol/g solid) and C is the phenol concentration
in water (mol/l). The minimum amount of solid (in grams) required per liter of
wastewater (up to one decimal place) is _____________.
GATE 2015
Answer: 6.4
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