chemical engineering Mcqs
1801. An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii) ____________________?
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A. Composition of the residue remains unchanged

B. More number of trays are required but the residue composition remains unchanged

C. More number of trays are required and the residue composition is more dilute in methanol

D. Less number of trays are required
1802. The relative saturation of an unsaturated mixture of gas and vapor is independent of the___________________?
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A. Nature of the vapor

B. None of these

C. Temperature of the mixture

D. Composition of the mixture

1803. According to Poiseuilles law, the permeability for gas flow through a capillary is proportional to (where, ? = gas viscosity)___________________?
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A. ?2

B. ?

C. ??

D. 1/?
1804. With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system) ?
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A. Increases Linearly

B. Remain unaffected

C. Decreases

D. Increases
1805. Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of _______________ humidity?
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A. Relative

B. None of these

C. Molal

D. Percentage

1806. The dew point of an unsaturated gas-vapor mixture does not depend upon the ____________________ of the mixture?
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A. Total pressure

B. Composition

C. Temperature

D. All A., B. and C.

1807. Pick out the wrong statement?
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A. The binary diffusivity in liquids is of the order of 10-5 cm2/sec

B. w of a gas through a given capillary

C. cess

D. Molecular diffusion in solid is much faster than that in liquids

E. Particles movement from higher concentration to lower concentration takes place in diffusion

F. According to Poiseuilles law, the permeability decreases with increase in temperature for

1808. To get high tray efficiency___________________?
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A. Interfacial surface between liquid and gas phase should be large

B. Liquid entrainment should be severe

C. Gas velocity should be very low

D. Time of contact between the two phases should be less

1809. Can the efficiency of a plate in the distillation tower be greater than 100% ?
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A. Yes

B. Yes; if the reflux ratio is maximum

C. Never

D. Normally not; but is possible if infinite number of plates are put

1810. Dry bulb temperature of the gas is _____________ the wet bulb temperature?
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A. None of these

B. Less than

C. More than

D. Equal to

1811. For a binary mixture with low relative volatility________________?
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A. Use high pressure distillation

B. Use molecular distillation

C. Use steam distillation

D. An azeotrope may be formed during distillation
1812. In case of non-ideal gases and liquids, the molal diffusivity ________________?
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A. Is independent of pressure

B. Varies directly as the pressure

C. Is equal to the volumetric diffusivity

D. Varies inversely as the pressure

1813. The falling rate period in the drying of a solid is characterised by__________________?
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A. Increase in rate of drying

B. Increasing temperatures both on the surface and within the solid

C. Decreasing temperatures

D. None of these

1814. Milk is dried usually in a __________________ dryer?
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A. Spray

B. Rotary

C. Tray

D. Freeze

1815. If Rm is the minimum reflux ratio, the optimum reflux ratio may be around _________________ Rm ?
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A. 2.5 to 3

B. 5

C. 1.2 to 1.5

D. 3 to 4

1816. Pick out the wrong statement ?
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A. In case of a packed tower, the operating velocity is about half of the flooding velocity,

B. idity</strong>

C. Change in barometric pressure does not affect the relative humidity

D. Elution means the desorption of the adsorbed solute by a solvent

E. The equilibrium moisture content of the solid can be reduced by increasing the absolute

F. erally

1817. For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause ____________________ plate requirement?
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A. Major decrease in the number of

B. Marginal decrease in the number of

C. No change in theoretical

D. None of these

1818. Removal of ______________ exemplifies an adsorption unit operation?
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A. Mustard oil from mustard seed

B. Water from petrol

C. Uranium from its ore

D. Ammonia from coke oven gas

1819. The Schmidt number which is defined as, ?/? D, is the ratio of the_____________________?
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A. None of these

B. Thermal diffusivity to the mass diffusivity

C. Momentum diffusivity to the mass diffusivity

D. Momentum diffusivity to the thermal diffusivity

1820. At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is ________________ percent.?
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A. 50

B. Between 0 and 100

C. 0

D. 100

1821. For an absorber, both equilibrium and operating line will be straight for _______________________?
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A. Concentrated solution and isothermal operation

B. Dilute solution and non-isothermal operation

C. Dilute solution and isothermal operation

D. Concentrated solution and non-isothermal operation

1822. Mass transfer co-efficient varies as DAB 0.5, according to the _______________ theory?
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A. None of these

B. Penetration

C. Surface renewal

D. Film

1823. Pick out the wrong statement?
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A. Mass transfer co-efficient does not account for gas-liquid diffusion

B. Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer

C. ration

D. Contacting cold vapor-gas mixture with hot liquid exemplifies humidification process

E. Contacting cold liquid with warm vapor-gas mixture exemplifies dehumidification process

1824. Reverse osmosis is also called_________________?
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A. Ultra-filtration

B. Dialysis

C. Diffusion

D. Electrodialysis

1825. Separation of the isotopes of helium for scientific investigations is done by_____________________?
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A. Leaching

B. Thermal diffusion

C. Solvent extraction

D. Reverse osmosis

1826. The relative saturation of a partially saturated mixture of vapour and gas can be increased by ________________ of the mixture?
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A. Reducing the total pressure

B. Increasing the total pressure

C. Reducing the temperature

D. Both B. and C.
1827. In McCabe-Thiele method, at infinite reflux ratio___________________?
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A. Number of plates is maximum

B. Overhead product is maximum

C. Both the operating lines coincide with the diagram

D. None of these

1828. At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbent __________________?
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A. Increases exponentially

B. Remains unchanged

C. Increases

D. Decreases
1829. Unit operation involved in the prilling of urea is_____________________?
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A. Evaporation

B. Drying

C. Crystallisation

D. Both B. and C.
1830. Cox chart is useful in the design of___________________?
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A. Evaporator

B. Distillation column

C. Crystalliser

D. Dryer

1831. Pick out the correct relationship. (Where, Ri = internal reflux ratio Ro = external reflux ratio.) ?
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A. (1 + Ri) = Ro/Ri

B. (1 Ri) = Ro/Ri

C. (1 Ro) = Ro/Ri

D. (1 + Ro) = Ro/Ri
1832. _______________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower?
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A. Lewis

B. Sherwood

C. Peclet

D. Stanton

1833. The temperature of water cooled in cooling tower is always _________________ temperature of entering air?
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A. Equal to the dry bulb

B. Equal to the wet bulb

C. More than the wet bulb

D. Less than the wet bulb

1834. Steady state equimolal counter diffusion is encountered in_____________________?
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A. All liquid-liquid diffusion systems

B. All liquid-solid diffusion systems

C. Separation of a binary mixture by distillation

D. Absorption of NH3 from air by water

1835. Mass transfer co-efficient is directly proportional to DAB according to the _____________ theory?
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A. Penetration

B. None of these

C. Surface-renewal

D. Film
1836. The cooling effect in a cooling tower cannot be increased by_____________________?
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A. Reducing the humidity of entering air

B. Increasing the air velocity over the wet surfaces

C. Lowering the barometric pressure

D. None of these
1837. According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity) ?
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A. D

B. 1/D

C. D0.5

D. D2

1838. The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will______________________?
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A. Decrease

B. Increase

C. Depend on saturated boiling point; may increase or decrease

D. Remain same

1839. Out of two equilibrium curves, first one lies above the diagonal and the second lies below the diagonal in the x-y plot. It means that separation by distillation is_________________?
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A. More readily done in the second case compared to first one

B. None of these

C. Not possible in the second case unless high pressure is applied

D. Not possible in the second case unless vacuum is applied

1840. Unsaturated air (with dry bulb temperature and dew point being 35C and 18C respectively) is passed through a water spray chamber maintained at 15C. The air will be cooled_________________?
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A. At the same relative humidity

B. And dehumidified with increase in wet bulb temperature

C. And dehumidified with decrease in wet bulb temperature

D. And humidified

1841. Acetic acid will be most economically separated from a dilute solution of acetic acid in water by____________________?
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A. Evaporation

B. Continuous distillation

C. Absorption

D. Solvent extraction
1842. It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%) ?
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A. 51 min

B. 71 min

C. 15 min

D. 94 min

1843. In the constant rate period of the rate of drying curve for batch drying,_________________?
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A. Rate of drying decreases abruptly

B. None of these

C. Cracks develop on the surface of the solid

D. Surface evaporation of unbound moisture occurs
1844. Mass transfer co-efficient is directly proportional to DAB according to the __________ theory?
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A. Film

B. None of these

C. Penetration

D. Surface-renewal

1845. Dorr thickener is an equipment used for______________________?
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A. Classification

B. Sedimentation

C. Leaching

D. Clarification

1846. At __________________ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation?
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A. Maximum permissible

B. Operating

C. Total

D. Minimum

1847. The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around_________________?
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A. 0.24

B. 600

C. 1

D. 3.97

1848. _________________ is the separation technique used for desalination of sea water ?
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A. Reverse osmosis

B. Absorption

C. Thermal diffusion

D. Adsorption

1849. Water entrained by circulating air in cooling towers is termed as____________________?
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A. Drift

B. Blow down

C. None of these

D. Vapor load

1850. Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the ________________ number?
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A. Schmidt

B. Sherwood

C. Stanton

D. Peclet