McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 251. |
Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2 . hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is |
| A. | 25% |
| B. | 50% |
| C. | 70% |
| D. | 90% |
| Answer» B. 50% | |
| 252. |
Mass transfer co-efficient is directly proportional to DAB 0.5, according to __________ theory. |
| A. | Penetration |
| B. | Surface renewal |
| C. | Film |
| D. | None of these |
| Answer» A. Penetration | |
| 253. |
Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty? |
| A. | Grid tray tower |
| B. | Perforated tray tower |
| C. | Wetted wall tower |
| D. | Bubble cap tower |
| Answer» D. Bubble cap tower | |
| 254. |
For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is |
| A. | Calculated |
| B. | Unknown |
| C. | Known |
| D. | Not required |
| Answer» C. Known | |
| 255. |
With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency |
| A. | Increases |
| B. | Decreases |
| C. | Remain same |
| D. | May increase or decrease; depends on individual design |
| Answer» A. Increases | |
| 256. |
Diameter to height ratio for a raschig ring is |
| A. | 1 |
| B. | 0.5 |
| C. | 2 |
| D. | 8 |
| Answer» A. 1 | |
| 257. |
Which of the following operations does not involve leaching? |
| A. | Dissolving gold from ores |
| B. | Dissolving pharmaceutical products from bark or roots |
| C. | Dissolving sugar from the cells of the beet |
| D. | Removing nicotine from its water solution by kerosene |
| Answer» D. Removing nicotine from its water solution by kerosene | |
| 258. |
Flooding in a distillation column is detected by a sharp |
| A. | Increase in Murphree plate efficiency |
| B. | Decrease in pressure drop |
| C. | Decrease in liquid hold up in the column |
| D. | Increase in pressure drop |
| Answer» D. Increase in pressure drop | |
| 259. |
In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction, |
| A. | Inversely |
| B. | Linearly |
| C. | Exponentially |
| D. | None of these |
| Answer» B. Linearly | |
| 260. |
With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system). |
| A. | Increases |
| B. | Decreases |
| C. | Remain unaffected |
| D. | Increases Linearly |
| Answer» A. Increases | |
| 261. |
Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if |
| A. | Mass transfer is accompanied by reaction |
| B. | Diffusion of A is in stagnant medium B |
| C. | Molecular mean free path is high |
| D. | There is equimolar counter diffusion |
| Answer» D. There is equimolar counter diffusion | |
| 262. |
Absorption accompanied by heat evolution results in |
| A. | Increased capacity of the absorber |
| B. | Increase in equilibrium solubility |
| C. | Decrease in equilibrium solubility |
| D. | None of these |
| Answer» C. Decrease in equilibrium solubility | |
| 263. |
The solvent used in liquid extraction should not have high latent heat of vaporisation, because |
| A. | The pressure drop and hence the pumping cost will be very high |
| B. | It cannot be recovered by distillation |
| C. | Its recovery cost by distillation may be prohibitively high |
| D. | It will decompose while recovering by distillation |
| Answer» C. Its recovery cost by distillation may be prohibitively high | |
| 264. |
Mass transfer co-efficient varies as DAB 0.5, according to the __________ theory. |
| A. | Film |
| B. | Surface renewal |
| C. | Penetration |
| D. | None of these |
| Answer» B. Surface renewal | |
| 265. |
The suitable evaporator for concentration of foaming liquids is a __________ evaporator. |
| A. | Long tube |
| B. | Short tube |
| C. | Vacuum |
| D. | Falling film |
| Answer» A. Long tube | |
| 266. |
In stripping section of continuous distillation column, the |
| A. | Liquid is stripped of high boiler |
| B. | Liquid is enriched with high boiler |
| C. | Vapour is stripped of low boiler |
| D. | None of these |
| Answer» B. Liquid is enriched with high boiler | |
| 267. |
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) |
| A. | Less number of trays are required |
| B. | Composition of the residue remains unchanged |
| C. | More number of trays are required but the residue composition remains unchanged |
| D. | More number of trays are required and the residue composition is more dilute in methanol |
| Answer» A. Less number of trays are required | |
| 268. |
The Schmidt number which is defined as, μ/ρ D, is the ratio of the |
| A. | Momentum diffusivity to the mass diffusivity |
| B. | Thermal diffusivity to the mass diffusivity |
| C. | Momentum diffusivity to the thermal diffusivity |
| D. | None of these |
| Answer» A. Momentum diffusivity to the mass diffusivity | |
| 269. |
NSc/NPr is called the |
| A. | Psychrometric ratio |
| B. | Lewis number |
| C. | Sherwood number |
| D. | Stanton number |
| Answer» B. Lewis number | |
| 270. |
At constant pressure, with increase of temperature, the dew point will |
| A. | Increase |
| B. | Decrease |
| C. | Remain unchanged |
| D. | Increase/decrease; depends on the temperature |
| Answer» A. Increase | |
| 271. |
Pick out the correct statement. |
| 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) |
| Answer» B. Electrodialysis is used in the manufacture of NaOH | |
| 272. |
The percentage humidity is less than the relative humidity only at __________ percent humidity. |
| A. | Zero |
| B. | Hundred |
| C. | Both zero and hundred |
| D. | None of these |
| Answer» C. Both zero and hundred | |
| 273. |
'ADDUCTS' and 'CLATHRATES' are used in case of |
| A. | Extractive distillation |
| B. | Crystallisation |
| C. | Absorption |
| D. | None of these |
| Answer» B. Crystallisation | |
| 274. |
__________ is concerned with the adsorption equilibria. |
| A. | Fick's law |
| B. | Gibb's equation |
| C. | Freundlich equation |
| D. | None of these |
| Answer» C. Freundlich equation | |
| 275. |
In most of the vacuum crystalliser, vacuum is generally produced by means of a |
| A. | Suction pump |
| B. | Compressed air jet |
| C. | Steam jet ejector with a barometric condenser |
| D. | None of these |
| Answer» C. Steam jet ejector with a barometric condenser | |
| 276. |
In a distillation column, with increase in the reflux ratio, the heat removed in the cooler |
| A. | Increases |
| B. | Decreases |
| C. | Remains unaffected |
| D. | And the heat required in reboiler decreases |
| Answer» A. Increases | |
| 277. |
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 |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | Depend on saturated boiling point; may increase or decrease |
| Answer» A. Increase | |
| 278. |
During constant rate drying period, vaporisation rate per unit drying surface area |
| A. | Decreases with time |
| B. | Increases with time |
| C. | Does not change with time |
| D. | Does not affect the moisture content of the wet solid |
| Answer» C. Does not change with time | |
| 279. |
A coalescer in a mixer-settler liquid-liquid extraction column |
| A. | Comprises of thin bed of substances of extended surface having high porosity |
| B. | Helps in increasing the bubble size entering the settler |
| C. | Helps in increasing the settling rate of the bubbles |
| D. | All 'a', 'b', & 'c' |
| Answer» D. All 'a', 'b', & 'c' | |
| 280. |
In which of the following unit operations, the selectivity is an important parameter? |
| A. | Distillation |
| B. | Solvent extraction |
| C. | Absorption |
| D. | None of these |
| Answer» B. Solvent extraction | |
| 281. |
Flash distillation is suitable for separating the constituents of a binary system, which |
| A. | Form minimum boiling azeotrope |
| B. | Have very wide boiling points |
| C. | Have very close boiling points |
| D. | Form constant boiling azeotrope |
| Answer» B. Have very wide boiling points | |
| 282. |
In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation. |
| A. | Lower than |
| B. | Higher than |
| C. | Equal to |
| D. | Either (A) or (B), depends on the mixture composition |
| Answer» A. Lower than | |
| 283. |
At __________ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation. |
| A. | Operating |
| B. | Total |
| C. | Minimum |
| D. | Maximum permissible |
| Answer» B. Total | |
| 284. |
Pick out the correct statement. |
| 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 |
| Answer» C. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux | |
| 285. |
In physical terms, Schmidt number means |
| A. | Thermal diffusivity/mass diffusivity |
| B. | Thermal diffusivity/momentum diffusivity |
| C. | Momentum diffusivity/mass diffusivity |
| D. | Mass diffusivity/thermal diffusivity |
| Answer» C. Momentum diffusivity/mass diffusivity | |
| 286. |
Unit operation involved in the prilling of urea is |
| A. | Evaporation |
| B. | Drying |
| C. | Crystallisation |
| D. | Both (B) and (C) |
| Answer» D. Both (B) and (C) | |
| 287. |
Degree of freedom for leaching and solvent extraction process is |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» D. 3 | |
| 288. |
With increase in temperature, the solubility of gases in liquids, at fixed pressure |
| A. | Increases |
| B. | Decreases |
| C. | Remain same |
| D. | Either (A) or (B), depends on the system |
| Answer» B. Decreases | |
| 289. |
The equipment used in the extraction of highly corrosive radioactive liquids is |
| A. | Pulse column |
| B. | Spray column |
| C. | Mixer settler |
| D. | Baffle tower |
| Answer» A. Pulse column | |
| 290. |
Tea percolation employs |
| A. | Liquid-liquid extraction |
| B. | Leaching |
| C. | Absorption |
| D. | None of these |
| Answer» B. Leaching | |
| 291. |
When the solvent dissolves very little of solute, then |
| A. | Solvent of low latent heat of vaporisation should be used |
| B. | Solvent of low freezing point should be used |
| C. | Large quantity of solvent is required to extract the solute |
| D. | Very small quantity of solvent is required |
| Answer» C. Large quantity of solvent is required to extract the solute | |
| 292. |
Bollman extractor |
| A. | Is a static bed leaching equipment |
| B. | Is used for extraction of oil from oilseed |
| C. | Is a centrifugal extractor |
| D. | Employs only counter-current extraction |
| Answer» B. Is used for extraction of oil from oilseed | |
| 293. |
In case of absorption, both the operating and equilibrium lines will be straight for |
| A. | Isothermal operation |
| B. | Dilute solutions |
| C. | Dilute solutions and isothermal operation |
| D. | None of these |
| Answer» C. Dilute solutions and isothermal operation | |
| 294. |
The most economical range of absorption factor is |
| A. | 0 to 0.5 |
| B. | 0 to 3 |
| C. | 1.25 to 2 |
| D. | 5 to 15 |
| Answer» C. 1.25 to 2 | |
| 295. |
In the constant rate period of the rate of drying curve for batch drying, |
| A. | Cracks develop on the surface of the solid |
| B. | Rate of drying decreases abruptly |
| C. | Surface evaporation of unbound moisture occurs |
| D. | None of these |
| Answer» C. Surface evaporation of unbound moisture occurs | |
| 296. |
Back-trapping in a distillation column |
| A. | Increases tray efficiency |
| B. | Decreases tray efficiency |
| C. | Reduces pressure drop |
| D. | Is desirable, as it provides improved vapour-liquid contact |
| Answer» B. Decreases tray efficiency | |
| 297. |
Rose oil is extracted from rose leaves using __________ distillation. |
| A. | High pressure |
| B. | Low pressure |
| C. | Extractive |
| D. | Steam |
| Answer» D. Steam | |
| 298. |
The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is |
| A. | 1 |
| B. | ∞ |
| C. | 0.5 |
| D. | 2 |
| Answer» B. ∞ | |
| 299. |
Pick out the wrong statement pertaining to the rotary dryer. |
| A. | Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell |
| B. | Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15 |
| C. | Rotary dryer is suitable for drying sticky material |
| D. | Recommended peripheral speed of a rotary drier is in the range of 10 to 30 metres/minute |
| Answer» C. Rotary dryer is suitable for drying sticky material | |
| 300. |
Which of the following is not a unit of mass transfer co-efficient? |
| A. | Moles transferred/ [(time) (area) (mole fraction)] |
| B. | Moles transferred/ [(time) (area) (mass A/mass B)] |
| C. | Moles transferred/ [(time) (area) (pressure)] |
| D. | None of these |
| Answer» D. None of these | |
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