The vapor
pressure of benzene and toluene are 3 and 4/3 atmospheres respectively. A
liquid feed of 0.4 moles of benzene and 0.6 moles of toluene is vapourised.
Assuming that the products are in equilibrium, the vapour phase mole fraction
of benzene is
(A)
0.4
(B)
0.6
(C)
0.8
(D)
0.2
GATE
1999
Answer: (B)
Sherwood number
in mass transfer is analogous to the following dimensionless group in heat
transfer
(A)
Graetz number
(B)
Grashoff number
(C)
Nusselt number
(D)
Prandtl number
GATE
1999
Answer: (C)
Penetration theory
states that the mass transfer coefficient is equal to (where De is diffusivity
and t is time)
(A)
(Det)1/2
(B)
(De/t)1/2
(C)
(4De/(πt))1/2
(D)
(4Det)1/2
GATE
1999
Answer: (C)
Solvent
used in extractive distillation
(A) is of low volatility
(B) forms a low boiling azeotrope
(C) forms a high boiling azeotrope
(D) Does not alter the relative volatility of
the original components
GATE
1999
Answer: (A)
In distillation
column design, the Maccabe-Thiele procedure is in adequate and Ponchon-Savrit
procedure is needed when
(A)
Saturated feed is not used
(B)
An azeotrope forms
(C)
The latent heat of vapourisation of the
more and less volatile components are greatly different
(D)
A total condenser is used
GATE
1998
Answer: (C)
If the prandtl number is greater than
the Schmidt number
(A)
The thermal boundary layer lies inside
the concentration boundary layer
(B)
The concentration boundary layer lies
inside the thermal boundary layer
(C)
The thermal and concentration boundary
layers are of equal thickness
(D)
The hydrodynamic (i.e. momentum)
boundary layer is thicker than the other two
GATE
1998
Answer: (A)
The mass
transfer coefficient for a solid sphere of radius ‘a’, dissolving in a large
volume of quiescent liquid in which D is the diffusivity of the solute is
(A)
D/a
(B)
D/2a
(C)
Proportional to D0.5
(D)
Dependent on Reynolds number
GATE 1998
Answer: (A)
In an inter
phase mass transfer process, the lesser the solubility of a given solute in a
liquid, the higher are the chances that the transfer process will be
(A)
Liquid phase resistance controlled
(B)
Gas phase resistance controlled
(C)
Impossible
(D)
Driven by a non-linear driving force
GATE
1998
Answer: (A)
In an inter
phase heat transfer process, the equilibrium state corresponds to equality of
temperatures in the two phases, while the condition for equilibrium in an
interphase mass transfer process is
(A)
Equality of concentrations
(B)
Equality of chemical potentials
(C)
Equality of activity coefficients
(D)
Equality of mass transfer coefficients
in both phases
GATE
1998
Answer: (B)
For the air – water system under ambient
conditions, the adiabatic saturation temperature and the wet-bulb temperature are
nearly equal, because
(A)
Water has a high latent heat of
vaporization
(B)
Lewis number is close to unity
(C)
They are always equal under all
circumstances
(D)
Solubility of the components of air in
water is very small
GATE 1998
Answer: (B)
For
a fixed number of ideal stages in a distillation column, as the reflux ratio is
increased, the difference in composition between the product streams
(A) increases
(B) decreases
(C) remains unchanged
(D) passes through a maximum
GATE
1998
Answer: (A)
In
distillation columns, the number of bubble caps per tray primarily depends on
the
(A) allowable liquid velocity
(B) allowable gas velocity
(C) allowable gas and liquid velocity
(D) fixed composition
GATE
1997
Answer: (B)
Molecular
diffusivity of a liquid
(A)
increases with temperature
(B)
decreases with temperature
(C)
may increase or decrease with
temperature
(D)
is independent of temperature
GATE 1997
Answer: (A)
For stripping of
a gas in a counter current stripper, the operating line
(A)
Lies above the equilibrium curve
(B)
Lies below the equilibrium curve
(C)
Can lie above or below the equilibrium
curve
(D)
Is always parallel
GATE
1997
Answer: (B)
In a binary
distillation column, if the feed contains 40 mole% vapour, the q-line will have
a slope of
(A)
1.5
(B)
-0.6
(C)
-1.5
(D)
0.6
GATE
1997
Answer: (C)
For turbulent
mass transfer in pipes, the Sherwood number depends upon the Reynolds number
(Re) as
(A)
Re0.33
(B)
Re0.53
(C)
Re0.83
(D)
Re
GATE 1997
Answer: (C)
In binary distillation, the separation
of the components is easier if the relative volatility (α) is
(A)
α >> 1
(B)
α << 1
(C)
α = 1
(D)
None of these
GATE
1997
Answer: (A)
When
a multistage tray tower uses a minimum reflux ratio it implies
(A) infinity trays and maximum reboiler heat
load
(B) infinite trays and minimum reboiler heat
load
(C) minimum trays and minimum reboiler heat
load
(D) minimum trays and maximum reboiler heat
load
GATE 1996
Answer: (B)
The
reason preferring packed towers over plate towers in distillation practice is
that the packed operation gives
(A) low pressure drop and high hold up
(B) high pressure drop and low hold up
(C) low pressure drop and low hold up
(D) high pressure drop and high hold up
GATE
1996
Answer: (C)
In distillation
where q is defined as the moles of liquid flow in the stripping section per
mole of feed introduced, for saturated liquid feed
(A)
q > 1
(B)
q < 1
(C)
q = 1
(D)
q = 0
GATE 1995
Answer: (C)
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