Mass Transfer

A. The binary diffusivity in liquids is of the order of 10-5 cm2/sec
B. Molecular diffusion in solid is much faster than that in liquids
C. Particles movement from higher concentration to lower concentration takes place in diffusion
process
D. According to Poiseuille’s law, the permeability decreases with increase in temperature for
flow of a gas through a given capillary

A. In case of induced draft cooling tower, the fan is placed at the top of the tower
B. Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and
hot discharged air
C. A natural draft cooling tower is recommended to be used, when the air humidity is low and air
temperature is also low
D. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb
temperature

A. Change in barometric pressure does not affect the relative humidity
B. In case of a packed tower, the operating velocity is about half of the flooding velocity,
generally
C. ‘Elution’ means the desorption of the adsorbed solute by a solvent
D. The equilibrium moisture content of the solid can be reduced by increasing the absolute
humidity

A. A horizontal line on the humidity chart indicates the temperature changes at constant molal
humidity
B. When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of
60°C, then both the approach & the range would be 10°C
C. For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature
& adiabatic cooling lines are the same
D. Relative saturation of unsaturated mixture of water vapor & air cannot be increased by either
reducing the mixture temperature or by increasing the total pressure

A. The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same
for NSc = NPr= 1
B. 1 Nm3 of dry air is lighter than 1Nm3 of humid air
C. The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass
diffusivity
D. An Azeotropic mixture of two liquids has boiling point higher than either of them, when it
shows negative deviation from Raoult’s Law

A. Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas
B. The ‘Hatta number’ is important in problems involving gas absorption without chemical
reaction
C. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both
components is linear in the case of steady state equimolal counter-diffusion
D. Total reflux in case of distillation operation requires infinite number of plates for a binary
system separation

A. Constant pressure distillation cannot separate an Azeotropic mixture
B. Relative volatility of a binary mixture changes appreciably with the minor change in
temperature
C. The relative volatility of a binary mixture at Azeotropic composition is unity
D. Flash distillation is practised on wide spread scale in petroleum refinery

A. Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the
number of theoretical stages required for the separation of non-ideal binary system by
distillation
B. A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn
C. Solvent used in extractive distillation should be of high volatility
D. Flash distillation is suitable for separating components which have very close boiling
temperature

A. Dialysis process is used for the production of fresh water from brine
B. Electrodialysis is used in the manufacture of NaOH
C. Electrodialysis is used for the refining/purification of petrol
D. Both B. and C.

A. The slope of the stripping line is always less than unity
B. For a given separation in a binary distillation column, with increase in reflux ratio (above the
minimum reflux ratio), the fixed cost of the distillation column first increases and then
decreases
C. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and
rectifying operating lines are vertical at total reflux
D. Kremser-Brown-Souder’s equation is used to calculate the efficiency of a plate tower