McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 101. |
The wet and 'dry bulb temperature for a vapour-gas mixture are 25°C and 30°C respectively. If the mixture is heated to 45°C at constant pressure, the wet bulb temperature will be __________ °C. |
| A. | 25 |
| B. | > 25 |
| C. | < 25 |
| D. | - 25 |
| Answer» B. > 25 | |
| 102. |
Water entrained by circulating air in cooling towers is termed as |
| A. | Drift |
| B. | Blow down |
| C. | Vapor load |
| D. | None of these |
| Answer» A. Drift | |
| 103. |
Pick out the wrong statement. Raoult's law does not apply, when the |
| A. | Size of component molecules are not equal |
| B. | Attractive forces between like and unlike molecules in the solution are approximately equal |
| C. | Component molecules are non-polar |
| D. | Chemical combination or molecular association between unlike molecules takes place in the formation of solution |
| Answer» C. Component molecules are non-polar | |
| 104. |
Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations. |
| A. | Sherwood number in mass transfer is analogous to Nusselt number in heat transfer |
| B. | Prandtl number in heat transfer is analogous to Schmidt number in mass transfer |
| C. | Reynolds number in mass transfer is analogous to Grashoff number in heat transfer |
| D. | Reynolds number remains the same in both heat and mass transfer |
| Answer» C. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer | |
| 105. |
Plate efficiency in a distillation column is reduced due to the __________ of liquid. |
| A. | Entrainment |
| B. | Foaming |
| C. | Weeping & dumping |
| D. | All (A), (B) & (C) |
| Answer» D. All (A), (B) & (C) | |
| 106. |
Pick out the wrong statement. |
| 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 operation |
| C. | Contacting cold vapor-gas mixture with hot liquid exemplifies humidification process |
| D. | Contacting cold liquid with warm vapor-gas mixture exemplifies dehumidification process |
| Answer» A. Mass transfer co-efficient does not account for gas-liquid diffusion | |
| 107. |
Blowdown in a cooling tower |
| A. | Means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities |
| B. | Increases the scale forming tendencies of water |
| C. | Is undesirable |
| D. | All (A), (B) & (C) |
| Answer» A. Means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities | |
| 108. |
Pick out the wrong statement. |
| A. | In solvent extraction, the distribution co-efficient should be as large as possible for solvent economy |
| B. | With increase in pressure, the solubility of gases in solvent increases at a fixed temperature |
| C. | Decrease in Murphree plate efficiency is an indication of entrainment in distillation column |
| D. | The capacity of a distillation column is maximum at total reflux |
| Answer» D. The capacity of a distillation column is maximum at total reflux | |
| 109. |
Rayleigh's equation applies to __________ distillation. |
| A. | Continuous |
| B. | Steam |
| C. | Differential |
| D. | Flash |
| Answer» C. Differential | |
| 110. |
In extraction, as the temperature increases, the area of heterogeneity (area covered by binodal curve) |
| A. | Decreases |
| B. | Increases |
| C. | Remains unchanged |
| D. | None of these |
| Answer» A. Decreases | |
| 111. |
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in |
| A. | Reducing the axial mixing |
| B. | Increasing the rate of extraction |
| C. | Maintaining the concentration difference between the two phases |
| D. | All 'a', 'b' & 'c' |
| Answer» D. All 'a', 'b' & 'c' | |
| 112. |
The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2 /m3 ) |
| A. | 500 |
| B. | 1200 |
| C. | 900 |
| D. | 800 |
| Answer» A. 500 | |
| 113. |
The slope of 9-line is determined by the |
| A. | Reflux ratio |
| B. | Plate efficiency to be achieved |
| C. | Thermal condition of the feed |
| D. | Relative volatility |
| Answer» C. Thermal condition of the feed | |
| 114. |
For a binary mixture with low relative volatility, |
| A. | Use steam distillation |
| B. | Use molecular distillation |
| C. | Use high pressure distillation |
| D. | An azeotrope may be formed during distillation |
| Answer» D. An azeotrope may be formed during distillation | |
| 115. |
Freundlich equation applies to the adsorption of solute from |
| A. | Dilute solutions, over a small concentration range |
| B. | Gaseous solutions at high pressure |
| C. | Concentrated solutions |
| D. | None of these |
| Answer» A. Dilute solutions, over a small concentration range | |
| 116. |
Pick out the wrong statement pertaining to the cooling towers. |
| 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 |
| Answer» D. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature | |
| 117. |
The Hatta number is important in |
| A. | Multi-component distillation |
| B. | Binary distillation |
| C. | Gas absorption without chemical reaction |
| D. | Gas absorption with chemical reaction |
| Answer» D. Gas absorption with chemical reaction | |
| 118. |
The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture. |
| A. | Composition |
| B. | Temperature |
| C. | Total pressure |
| D. | All (A), (B) and (C) |
| Answer» B. Temperature | |
| 119. |
A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls /ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)) |
| A. | M(Xo - XF) |
| B. | M(Xo/XF) |
| C. | M ln(Xo/XF) |
| D. | MXo ln(Xo/XF) |
| Answer» D. MXo ln(Xo/XF) | |
| 120. |
In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is |
| A. | Equal to the heat of formation of surface compound |
| B. | Equal to the heat of wetting |
| C. | Zero |
| D. | Called integral heat of adsorption |
| Answer» B. Equal to the heat of wetting | |
| 121. |
The critical moisture content in case of drying indicates the __________ rate period. |
| A. | Beginning of falling |
| B. | Beginning of constant |
| C. | End of falling |
| D. | None of these |
| Answer» A. Beginning of falling | |
| 122. |
Pick out the wrong statement. |
| 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 |
| Answer» B. Molecular diffusion in solid is much faster than that in liquids | |
| 123. |
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. |
| A. | Molal |
| B. | Relative |
| C. | Percentage |
| D. | None of these |
| Answer» A. Molal | |
| 124. |
Separation of two volatile liquids by distillation makes use of their |
| A. | Selectivity |
| B. | Relative volatility |
| C. | Solubility |
| D. | Density difference |
| Answer» B. Relative volatility | |
| 125. |
Powdery materials can be guarded against caking tendency on storage by |
| A. | Providing irregular grain size |
| B. | Providing minimum percentage of voids |
| C. | Having maximum possible points of contact |
| D. | None of these |
| Answer» D. None of these | |
| 126. |
The minimum liquid rate to be used in an absorber corresponds to an operating line |
| A. | Of slope = 1 |
| B. | Of slope = 0.1 |
| C. | Tangential to the equilibrium curve |
| D. | None of these |
| Answer» C. Tangential to the equilibrium curve | |
| 127. |
Leaching of uranium ore and gold ore is done in |
| A. | Centrifugal extractor |
| B. | Pachuca tanks |
| C. | Bollman extractor |
| D. | None of these |
| Answer» B. Pachuca tanks | |
| 128. |
The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is |
| A. | 0 |
| B. | ∞ |
| C. | -ve |
| D. | +ve |
| Answer» C. -ve | |
| 129. |
For a ternary mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates. |
| A. | Binary mixture is represented by the apex |
| B. | Binary mixture is represented by any point inside |
| C. | Ternary mixture is represented by the sides |
| D. | Pure component is represented by the apex |
| Answer» D. Pure component is represented by the apex | |
| 130. |
In a gas-liquid absorption column, for obtaining the maximum absorption efficiency |
| A. | Liquid stream should be distributed uniformly |
| B. | Gas stream should be distributed uniformly |
| C. | Both gas as well as liquid streams should be distributed uniformly |
| D. | By passing should be completely avoided |
| Answer» C. Both gas as well as liquid streams should be distributed uniformly | |
| 131. |
To get high tray efficiency |
| A. | Interfacial surface between liquid and gas phase should be large |
| B. | Time of contact between the two phases should be less |
| C. | Gas velocity should be very low |
| D. | Liquid entrainment should be severe |
| Answer» A. Interfacial surface between liquid and gas phase should be large | |
| 132. |
Lewis number (Le) is |
| A. | Sc × Pr |
| B. | Pr × St |
| C. | Sh × Pr |
| D. | St × Sh |
| Answer» A. Sc × Pr | |
| 133. |
Which is not concerned directly with mass transfer? |
| A. | Schmidt number |
| B. | Sherwood number |
| C. | Lewis relationship |
| D. | Froude number |
| Answer» D. Froude number | |
| 134. |
Most important factor to be considered in the selection of packings for absorbers is the __________ of packing. |
| A. | Size |
| B. | Durability |
| C. | Porosity |
| D. | Cost |
| Answer» C. Porosity | |
| 135. |
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement. |
| A. | No change in theoretical |
| B. | Marginal decrease in the number of |
| C. | Major decrease in the number of |
| D. | None of these |
| Answer» B. Marginal decrease in the number of | |
| 136. |
Experimental determination of __________ is done by wetted wall column method. |
| A. | Diffusion co-efficient |
| B. | Mass transfer co-efficient |
| C. | NTU |
| D. | None of these |
| Answer» B. Mass transfer co-efficient | |
| 137. |
Ammonia present in the coke oven gas is removed by washing with |
| A. | Caustic solution |
| B. | Dilute ammoniacal liquor |
| C. | Dilute HCl |
| D. | Ethanolamine |
| Answer» B. Dilute ammoniacal liquor | |
| 138. |
Which of the following provides maximum contact surface for a liquid-vapour system? |
| A. | Packed tower |
| B. | Bubble-cap plate column |
| C. | Sieve-plate column |
| D. | Wetted wall column |
| Answer» A. Packed tower | |
| 139. |
At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes |
| A. | 1 |
| B. | 0 |
| C. | ∞ |
| D. | None of these |
| Answer» C. ∞ | |
| 140. |
Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ column. |
| A. | Spray |
| B. | Packed |
| C. | Bubble cap plate |
| D. | Wetted wall |
| Answer» D. Wetted wall | |
| 141. |
Which of the following is directly concerned with Psychrometry? |
| A. | Lewis relationship |
| B. | Galileo number |
| C. | Weber number |
| D. | Dean number |
| Answer» A. Lewis relationship | |
| 142. |
In the layout plan for a vacuum distillation unit, operating at 60 mm Hg, supported by a barometric condenser, the appropriate place for the location of vacuum drum for collecting the distillate will be |
| A. | At ground level |
| B. | 2 metres above the ground |
| C. | 5 metres above ground |
| D. | 10 metres above ground |
| Answer» A. At ground level | |
| 143. |
Which of the following is an undesirable property in a tower packing? |
| A. | Large surface per unit volume |
| B. | Large free cross-section |
| C. | Low weight per unit volume |
| D. | Large weight of liquid retained |
| Answer» D. Large weight of liquid retained | |
| 144. |
High pressure at the bottom of a distillation tower handling heat sensitive materials results in |
| A. | Thermal decomposition of bottoms |
| B. | Increased relative volatility |
| C. | Erosion of the tower |
| D. | Very efficient operation |
| Answer» A. Thermal decomposition of bottoms | |
| 145. |
Steady state equimolal counter diffusion is encountered in |
| A. | Separation of a binary mixture by distillation |
| B. | Absorption of NH3 from air by water |
| C. | All liquid-liquid diffusion systems |
| D. | All liquid-solid diffusion systems |
| Answer» A. Separation of a binary mixture by distillation | |
| 146. |
Minimum reflux ratio in a distillation column results in |
| A. | Optimum number of trays |
| B. | Minimum reboiler size |
| C. | Maximum condenser size |
| D. | Minimum number of trays |
| Answer» C. Maximum condenser size | |
| 147. |
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 |
| Answer» C. -1.5 | |
| 148. |
The individual mass transfer co-efficients (moles/m2 s) for absorption of a solute from a gas mixture into a liquid solvent are, KL = 4.5 and KG = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling? |
| A. | Liquid side |
| B. | Gas side |
| C. | Interfacial |
| D. | Both liquid and gas side |
| Answer» B. Gas side | |
| 149. |
Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the __________ temperature. |
| A. | Dry-bulb |
| B. | Wet-bulb |
| C. | Dew point |
| D. | Adiabatic saturation |
| Answer» B. Wet-bulb | |
| 150. |
In case of unsaturated air |
| A. | Dew point < wet bulb temperature |
| B. | Wet bulb temperature < dry bulb temperature |
| C. | Both (A) and (B) |
| D. | Neither (A) not (B) |
| Answer» C. Both (A) and (B) | |
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