chemical engineering MCQs – Page 91

Practise multiple-choice questions from chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

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