McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 201. |
According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity) |
| A. | μ |
| B. | 1/μ |
| C. | √μ |
| D. | μ2 |
| Answer» B. 1/μ | |
| 202. |
Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the |
| A. | High evaporation losses of water |
| B. | High pressure drop of the gas |
| C. | Difficulty in its fabrication |
| D. | None of these |
| Answer» B. High pressure drop of the gas | |
| 203. |
In case of constant underflow extraction operation, the __________ at all solute concentration. |
| A. | Solids are drained to the same extent |
| B. | Ratio of the insoluble to solution is constant |
| C. | Both (A) & (B) |
| D. | Neither (A) nor (B) |
| Answer» C. Both (A) & (B) | |
| 204. |
Which of the following has the same dimension as mass diffusivity? |
| A. | Momentum flux |
| B. | Kinematic viscosity |
| C. | Thermal diffusivity |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 205. |
Packed column distillation is limited to the column __________ metres. |
| A. | Height < 6 |
| B. | Diameter < 0.6 |
| C. | Both (A) & (B) |
| D. | Neither (A) nor (B) |
| Answer» C. Both (A) & (B) | |
| 206. |
Which of the following decreases during evaporative cooling process with recirculated water supply? |
| A. | Wet bulb temperature |
| B. | Relative humidity |
| C. | Partial pressure of vapour |
| D. | None of these |
| Answer» D. None of these | |
| 207. |
During constant rate period, the rate of drying decreases with the |
| A. | Decrease in air temperature |
| B. | Increase in air humidity |
| C. | Both (A) and (B) |
| D. | Neither (A) nor (B) |
| Answer» C. Both (A) and (B) | |
| 208. |
At what percentage (by volume) of alcohol composition, it forms an azeotrope with water? |
| A. | 90 |
| B. | 91.5 |
| C. | 95 |
| D. | 99 |
| Answer» C. 95 | |
| 209. |
Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method? |
| A. | Partial condenser |
| B. | Total condenser |
| C. | Reboiler |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 210. |
Steam distillation is not recommended to be used, if the |
| A. | Azeotropic mixture is to be separated and the final product is miscible with water |
| B. | Liquids decompose, if distilled directly at atmospheric pressure |
| C. | Material cannot be distilled by indirect heating even under low pressure, because of the high boiling temperature |
| D. | Material to be distilled is thermally unstable or has the tendency to react with other components associated with it, at the boiling temperature |
| Answer» A. Azeotropic mixture is to be separated and the final product is miscible with water | |
| 211. |
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%). |
| A. | 15 min |
| B. | 51 min |
| C. | 71 min |
| D. | 94 min |
| Answer» C. 71 min | |
| 212. |
In Azeotropic mixture, the equilibrium vapour composition is |
| A. | More than liquid composition |
| B. | Less than liquid composition |
| C. | Same as liquid composition |
| D. | Independent of pressure |
| Answer» C. Same as liquid composition | |
| 213. |
In rectifying section of a continuous distillation column, the |
| A. | Vapour is enriched with low boilers |
| B. | Vapour is enriched with high boilers |
| C. | Liquid is stripped of high boilers |
| D. | None of these |
| Answer» B. Vapour is enriched with high boilers | |
| 214. |
The reason for preferring packed towers over plate towers in distillation practice is that the packed tower 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 |
| Answer» C. Low pressure drop and low hold up | |
| 215. |
Diameter of raschig rings used in packed tower in industry is normally around __________ inches. |
| A. | 2 |
| B. | 8 |
| C. | 12 |
| D. | 18 |
| Answer» A. 2 | |
| 216. |
The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model. |
| A. | Plug |
| B. | Perfectly mixed |
| C. | Both (A) & (B) |
| D. | Neither (A) nor (B) |
| Answer» B. Perfectly mixed | |
| 217. |
Plate efficiency |
| A. | Is a function of the mass transfer between liquid and vapour |
| B. | Increases due to foaming |
| C. | Increases due to liquid entrainment |
| D. | Increases due to weeping and dumping of liquid |
| Answer» A. Is a function of the mass transfer between liquid and vapour | |
| 218. |
Weeping in a distillation column |
| A. | Increases tray efficiency |
| B. | Provides large interfacial surface for mass transfer |
| C. | Results due to very high gas velocity |
| D. | Results due to very low gas velocity |
| Answer» D. Results due to very low gas velocity | |
| 219. |
The expression, y(1 - x)/x(1 - y) is for |
| A. | Absorption factor |
| B. | Relative volatility |
| C. | Selectivity |
| D. | Murphree efficiency |
| Answer» B. Relative volatility | |
| 220. |
The process employing desorption of the absorbed solute by a solvent is called |
| A. | Elution |
| B. | Osmosis |
| C. | Reverse osmosis |
| D. | Sublimation |
| Answer» A. Elution | |
| 221. |
In McCabe-Thiele method, at infinite reflux ratio |
| A. | Number of plates is maximum |
| B. | Overhead product is maximum |
| C. | Both the operating lines coincide with the diagram |
| D. | None of these |
| Answer» C. Both the operating lines coincide with the diagram | |
| 222. |
Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the |
| A. | Packing may be crushed due to thermal expansion/contraction of the components of the equipments |
| B. | Pressure drop in the equipment will be very high |
| C. | Viscosity variation of the fluids may cause channelling/flooding |
| D. | None of these |
| Answer» A. Packing may be crushed due to thermal expansion/contraction of the components of the equipments | |
| 223. |
Pick out the correct statement. |
| 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 |
| Answer» 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 | |
| 224. |
A binary mixture of benzene and cyclohexane is separated by |
| A. | Flash vaporisation |
| B. | Extractive distillation |
| C. | Solvent extraction |
| D. | Ordinary distillation |
| Answer» B. Extractive distillation | |
| 225. |
Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as |
| A. | D 0.5 |
| B. | D |
| C. | 1/D |
| D. | D 1.5 |
| Answer» A. D 0.5 | |
| 226. |
Free flowing granular materials can be best dried in a __________ drier. |
| A. | Rotary |
| B. | Cylinder |
| C. | Drum |
| D. | Freeze |
| Answer» A. Rotary | |
| 227. |
In a packed bed absorption column, the channelling will be noted by the |
| A. | Increase in flow rate |
| B. | Sharp drop in pressure drop |
| C. | Sharp rise in pressure drop |
| D. | None of these |
| Answer» B. Sharp drop in pressure drop | |
| 228. |
The ratio of Murphree plate efficiency to point efficiency is always > 1 in a __________ flow model. |
| A. | Plug |
| B. | Perfectly mixed |
| C. | Both (A) & (B) |
| D. | Neither (A) nor (B) |
| Answer» A. Plug | |
| 229. |
Fractional solvent extraction |
| A. | Employs only one solvent |
| B. | Employs two solvents |
| C. | Results in low interfacial tension |
| D. | None of these |
| Answer» B. Employs two solvents | |
| 230. |
At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid __________ that in dry packed tower. |
| A. | Is greater than |
| B. | Is lower than |
| C. | Is same as |
| D. | Cannot be predicted as data are insufficient |
| Answer» A. Is greater than | |
| 231. |
During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant. |
| A. | Wet bulb temperature |
| B. | Partial pressure of water vapor |
| C. | Relative humidity |
| D. | None of these |
| Answer» A. Wet bulb temperature | |
| 232. |
Wet bulb and dry bulb temperatures becomes identical at __________ percent saturation curve. |
| A. | 100 |
| B. | 50 |
| C. | 78 |
| D. | None of these |
| Answer» A. 100 | |
| 233. |
__________ is the separation technique used for desalination of sea water. |
| A. | Thermal diffusion |
| B. | Reverse osmosis |
| C. | Adsorption |
| D. | Absorption |
| Answer» B. Reverse osmosis | |
| 234. |
The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law. |
| A. | Exponential |
| B. | Parabolic |
| C. | Linear |
| D. | Cubic |
| Answer» A. Exponential | |
| 235. |
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 |
| A. | Not possible in the second case unless vacuum is applied |
| B. | Not possible in the second case unless high pressure is applied |
| C. | More readily done in the second case compared to first one |
| D. | None of these |
| Answer» C. More readily done in the second case compared to first one | |
| 236. |
According to Chilton-Colburn analogy for mass transfer, NSt.NSc 2/3 is equal to |
| A. | f |
| B. | f/2 |
| C. | 2f |
| D. | 1/f |
| Answer» B. f/2 | |
| 237. |
Very tall packed towers are divided into series of beds to |
| A. | Reduce the overall pressure drop |
| B. | Avoid channelling |
| C. | Reduce liquid hold-up |
| D. | Avoid flooding |
| Answer» B. Avoid channelling | |
| 238. |
If „f’ is defined as above, then which of the following applies to a feed at dew point? |
| A. | f = 1 |
| B. | f < 1 |
| C. | f > 1 |
| D. | 0 < f < 1 |
| Answer» A. f = 1 | |
| 239. |
Separation of the isotopes of helium for scientific investigations is done by |
| A. | Reverse osmosis |
| B. | Thermal diffusion |
| C. | Leaching |
| D. | Solvent extraction |
| Answer» B. Thermal diffusion | |
| 240. |
Flash distillation is suitable for the separation of components |
| A. | Having very close boiling points |
| B. | Which form maximum boiling azeotrope |
| C. | Having very wide boiling points |
| D. | Which form minimum boiling azeotrope |
| Answer» C. Having very wide boiling points | |
| 241. |
The McCabe ΔL law states that the |
| A. | Molar heats of vaporisation of components are nearly equal |
| B. | Linear crystal growth rate depends on the degree of super-saturation |
| C. | Linear crystal growth rate does not depend on the crystal size |
| D. | Linear crystal growth rate depends on the crystal size |
| Answer» C. Linear crystal growth rate does not depend on the crystal size | |
| 242. |
When both the fluids flow concurrently in an absorber, the slope of the operating line is |
| A. | -ve |
| B. | +ve |
| C. | 1 |
| D. | -1 |
| Answer» A. -ve | |
| 243. |
Steam distillation is used for separation of high boiling |
| A. | Substances from non-volatile impurities |
| B. | Volatile impurity from still higher boiling substances |
| C. | Both (A) and (B) |
| D. | Neither (A) nor (B) |
| Answer» C. Both (A) and (B) | |
| 244. |
The relative saturation of a partially saturated mixture of vapour and gas can be increased by __________ of the mixture. |
| A. | Reducing the total pressure |
| B. | Increasing the total pressure |
| C. | Reducing the temperature |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 245. |
Pick out the correct statement. |
| 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 |
| Answer» 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 | |
| 246. |
Pick out the wrong statement. |
| 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 |
| Answer» B. Relative volatility of a binary mixture changes appreciably with the minor change in temperature | |
| 247. |
For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams |
| A. | Increases |
| B. | Decreases |
| C. | Remain unaffected |
| D. | Passes through a maximum |
| Answer» A. Increases | |
| 248. |
__________ diffusion is used for separating the isotopes of methane. |
| A. | Thermal |
| B. | Pressure |
| C. | Concentration |
| D. | Force |
| Answer» A. Thermal | |
| 249. |
Pick out the wrong statement. |
| A. | The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one |
| B. | Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference |
| C. | According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 |
| D. | The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz |
| Answer» C. According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 | |
| 250. |
For a distillation column operating at minimum reflux, the |
| A. | Concentration of liquid and vapour leaving a plate will be same |
| B. | Reflux ratio will be maximum |
| C. | Number of plates required will be maximum |
| D. | None of these |
| Answer» C. Number of plates required will be maximum | |
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