chemical engineering Mcqs
2251. _______________ is a cohesive solid ?
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A. Sand

B. Wheat

C. Wet clay

D. None of these

2252. Float and sink test determines the possibility of cleaning of coal by a process based on the___________________?
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A. None of these

B. Wettability

C. Particle shape

D. Gravity separation
2253. Which of the following remains constant during sensible cooling process ?
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A. Specific humidity

B. Partial pressure of vapour

C. Both A. and B.

D. Neither A. nor B.

2254. Optimum ratio of operating speed to critical speed of a trommel is_____________________?
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A. 1.5-2.5

B. 0.5-2

C. 0.33-0.45

D. 1.33-1.45

2255. Ultracentrifuges running at speeds upto 100000 rpm is normally used for the_____________________?
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A. Dewaxing of lubricating oil

B. Separation of isotopes based on their density or molecular weights difference

C. Separation of cream from milk

D. Concentration of rubber latex

2256. Which of the following crushing laws is most accurately applicable to the fine grinding of materials ?
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A. None of these

B. Rittingers law

C. Bonds crushing law

D. Kicks law

2257. In classification, particles are said to be equal settling, if they have the same terminal velocities in the_______________?
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A. Different fluids

B. Same fluid

C. Same field of force

D. Both B. and C.
2258. Shell and leaf filter as compared to plate and frame filter _____________________?
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A. Provides more effective washing

B. Facilitates filtration under higher pressure

C. All A., B. & C.

D. Entails less labor cost

2259. Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity ?
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A. Raschig rings

B. Sphere

C. Cylinder (L/D = 1)

D. Cube

2260. Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the___________________?
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A. Coagulation

B. Clarification

C. Sedimentation

D. Flocculation

2261. In constant pressure filtration ?
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A. Rate of filtration increases with time

B. Rate of filtration decreases with time

C. Rate of filtration is constant

D. Resistance decreases with time

2262. Solid particles of different densities are separated by _____________________?
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A. Filters

B. Thickness

C. Sorting classifier

D. Cyclones

2263. The most suitable equipment used to devulcanise rubber scrap and to make water dispersion & rubber solution is a __________________?
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A. Propeller agitator

B. Boundary mixer

C. Sharpies centrifuge

D. None of these

2264. Angle of nip of the crushing rolls does not depend upon the_______________?
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A. Product size

B. Feed size

C. Speed of the rolls

D. Diameter of the rolls

2265. The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of feed and product respectively) ?
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A. Dp/Df

B. Df/Dp

C. None of these

D. Df Dp

2266. The binary diffusivity in gases does not depend upon the ___________________?
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A. Temperature

B. Pressure

C. Nature of the components

D. None of these
2267. Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is________________?
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A. > 100

B. < 100

C. < 10

D. > 10

2268. Length/diameter ratio of a ball mill is __________________ ?
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A. 1

B. > 1

C. 1.5

D. < 1
2269. For sizing of fine materials, the most suitable equipment is a____________________?
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A. Vibrating screen

B. Shaking screen

C. Trommel

D. Grizzly

2270. What is the reduction ratio in a fine crushing operation having following feed and product sizes ?
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A. 5

B. 10

C. 2

D. 0.5

2271. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?
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A. Nc = (1/4?). ?(g/R1 R2)

B. Nc = (1/2?). ?(R1 R2/g)

C. Nc = (1/2?). ?(g/R1 R2)

D. Nc = (1/?). ?(g/R1 R2)

2272. Grinding efficiency of a ball mill is of the order of _______________ percent?
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A. 1-5

B. 75-80

C. 40-50

D. 90-95

2273. The most common packing used in industrial operations is _______________ rings?
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A. Single spiral

B. Cross-partition

C. Lessing

D. Raschig
2274. Fluid energy mill comes in the category of________________?
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A. Grinder

B. Ultrafine grinder

C. Cutter

D. Crusher

2275. The opening of a 200 mesh screen (Taylor series) is__________________?
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A. 0.0074 mm

B. 0.0047 cm

C. 0.0074 cm

D. 74 milli-microns

2276. Pine oil used in froth floatation technique acts as a/an_____________________?
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A. Collector

B. Modifier

C. Frother

D. Activator

2277. Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator ?
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A. Cresylic acid

B. Copper sulphate

C. Sodium carbonate

D. Calcium carbonate

2278. In a size reduction crushing operation, the feed size is 10 to 50 mm, while the product size is 2 to 10 mm. This is a case of _______________ crushing?
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A. Primary

B. Ultrafine

C. Fine

D. Secondary

2279. The main differentiation factor between tube mill and ball mill is the ___________________?
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A. Size of the grinding media

B. Operating speed

C. Length to diameter ratio

D. Final product size

2280. Maximum size reduction in a ball mill is done by the, ______________ action?
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A. Attrition

B. Cutting

C. Compression

D. Impact
2281. Which of the following achieves the least reduction ratio for a given feed size ?
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A. Jaw crusher

B. Roll crusher

C. Cone crusher

D. Gyratory crusher

2282. The specific cake resistance for compressible sludges is a function of the pressure drop__________________?
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A. None of these

B. Over cake

C. Overall

D. Over medium

2283. Kicks law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kicks constant is_________________?
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A. kg/sec

B. kWh/sec. kg

C. kWh/kg

D. kW. sec/kg
2284. Which of the following is the hardest material ?
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A. Calcite

B. Corundum

C. Gypsum

D. Quartz

2285. A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for _______________ flow of filtrate?
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A. Compressible cake and turbulent

B. Compressible cakes and laminar

C. Incompressible cake and laminar

D. Incompressible cake and turbulent

2286. _______________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution?
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A. Muller

B. Banbury

C. Tumbler

D. Ribbon blender

2287. Solvent used in extractive distillation___________________?
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A. Should be of high volatility

B. All A., B. and C.

C. Changes the relative volatility of the original components

D. Should form azeotropes with the original components

2288. In case of a ball mill ?
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A. Operating speed should be more than the critical speed

B. Fine feed requires a larger ball

C. Coarse feed requires a larger ball

D. None of these

2289. At equilibrium the concentration of water in vapour phase (C*) in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is_________________?
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A. 0.4

B. 1

C. 0

D. 0.2

2290. A tube mill as compared to a ball mill__________________?
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A. All A., B. and C.

B. Employs smaller balls

C. Has larger length/diameter ratio (>2 as compared to 1 for ball mill)

D. Gives finer size reduction but consumes more power

2291. Which of the following is not a part of the Blake jaw crusher ?
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A. Pitman

B. Hanger

C. Check plates

D. Toggles

2292. Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called__________________?
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A. Clarification

B. Thickening

C. Froth floatation

D. Classification
2293. Rittingers number designates the new surface created per unit mechanical energy absorbed by the material being crushed. Larger value of Rittingers number of a material indicates its________________?
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A. Easier grindability

B. High power consumption in grinding

C. Poor grindability

D. None of these

2294. Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively ?
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A. 1000C and 10 atm

B. 1000C and 500 atm

C. 200C and 5 atm

D. 500C and 50 atm

2295. A fluid energy mill is used for __________________?
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A. Crushing

B. Ultra-grinding

C. Cutting

D. Grinding

2296. Introduction of slurry in a plate and frame filter press is done through a plate in each frame. The plate of this filter has a _______________ surface?
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A. Curved

B. Ribbed

C. Either A. or B.

D. Plane

2297. Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is_______________?
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A. Pre-coated on the filter medium prior to filtration

B. All A, B. & C.

C. Separated from the cake by dissolving solids or by burning it off

D. Added to the feed slurry

2298. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about _______________ percent of the volume of the mill?
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A. 70

B. 35

C. 50

D. 85

2299. Size reduction of fibrous materials like wood, asbestos, mica etc. is done by a disintegrator exemplified by the _________________?
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A. Stamp mill

B. Bradfords breaker

C. Cage mill

D. Blake jaw crusher

2300. Filtration rate through a filter cake is proportional to (where, S = filtering surface R = specific cake resistance ? = viscosity of the filtrate) ?
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A. All A., B. & C.

B. 1/R

C. 1/?

D. S