All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 271 of 350
- A. 1.5-2.5
- B. 3.5-5.5
- C. 7.5-10.0
- D. 10-15
Explanation: Rotary dryers are commonly designed with about 1.5 to 2.5 transfer units, even though their length-to-diameter ratio is typically 4 to 10.
Correct answer: 1.5-2.5- A. 1/5th
- B. 1/15th
- C. 1/30th
- D. 1/50th
Explanation: Random packing must be small relative to the column to distribute liquid properly and avoid excessive wall effects.
Correct answer: 1/15th- A. Twice
- B. Equal to
- C. 0.6-0.8 times
- D. 2 ft irrespective of (for column > 3 ft diameter)
Explanation: The straight weir on a cross-flow tray is usually shorter than the column diameter, with a length of approximately 0.6 to 0.8 times the…
Correct answer: 0.6-0.8 times- A. 2-3
- B. 18-22
- C. 12-15
- D. 6-8
Explanation: Rotary dryer shells must be thick enough to resist mechanical loads and deformation while remaining economical; a typical shell thickness…
Correct answer: 6-8- A. Both B. and C.
- B. A hold down bar
- C. Bolts
- D. Rivets
Explanation: Bubble caps must be restrained against lifting and are commonly secured using hold-down bars or bolts.
Correct answer: Both B. and C.- A. Clearance of 25-75 mm
- B. Either A. or B.
- C. Cap pitch of 1.3-2 times the cap diameter
- D. Neither A. nor B.
Explanation: Bubble-cap layouts commonly use a clearance of roughly 25 to 75 mm and a pitch around 1.3 to 2 times the cap diameter.
Correct answer: Either A. or B.- A. Sieve
- B. Valve
- C. Counter flow
- D. Bubble cap
Explanation: Bubble-cap trays have risers, caps, and liquid seals that create greater resistance to vapor flow than sieve or valve trays under…
Correct answer: Bubble cap- A. Both B. & C.
- B. Increases economy
- C. Does not affect the capacity
- D. Increases capacity
Explanation: Multiple-effect evaporation reuses vapour from one effect to heat the next, so less live steam is needed per unit of evaporation and steam…
Correct answer: Both B. & C.5409. Bubble cap tray is the most commonly used tray in large distillation column, because______________?
- A. It incurs less pressure drop as compared to any other try designed for the same duty
- B. Of its flexibility and nearly constant efficiency under varying conditions of operation
- C. It eliminates the foaming and entrainment tendency during operation
- D. None of these
Explanation: Bubble-cap trays tolerate a wide range of vapour and liquid flow rates while maintaining nearly constant efficiency, giving them good…
Correct answer: Of its flexibility and nearly constant efficiency under varying conditions of operation- A. Downcomer liquid seal in case of a balanced tray design
- B. Static submergence in case of a bubble cap tray for column operating under pressure (≥ 1 atm)
- C. All A., B. and C.
- D. Skirt clearance for bubble caps
Explanation: The range of about 1.2 to 3.8 cm is used as a typical design range for the downcomer seal, bubble-cap static submergence, and cap skirt…
Correct answer: All A., B. and C.- A. Type & size of packing
- B. Fluid rates and fluid properties
- C. All A., B. and C.
- D. Operating pressure and column diameter
Explanation: Packed-tower stage efficiency is influenced by packing characteristics, liquid and vapour rates, fluid properties, pressure, and column…
Correct answer: All A., B. and C.- A. Small downcomer liquid seal
- B. Lower skirt clearance
- C. Lower static submergence
- D. Liquid gradient on the tray
Explanation: A liquid-level gradient across a tray produces different liquid heads over the bubble caps, so the vapour does not divide equally among…
Correct answer: Liquid gradient on the tray- A. Packed
- B. Sieve plate
- C. Bubble cap plate
- D. None of these
Explanation: Packed towers are preferred for highly corrosive fluids because packing can be made from corrosion-resistant materials and provides no…
Correct answer: Packed5414. What is the slope of the feed line, if the feed to a distillation column is a saturated liquid ?
- A. 0
- B. > 1
- C. ∞
- D. < 1
Explanation: The feed-line slope is q/(q−1). For saturated liquid feed, q = 1, so the denominator becomes zero and the q-line is vertical, giving an…
Correct answer: ∞- A. 1.5 to 3
- B. 1.6 to 2
- C. 2.5
- D. 1.3 to 2
Explanation: Bubble-cap tray spacing is selected to leave adequate room for vapor flow and liquid movement while maintaining effective contact; a…
Correct answer: 1.3 to 2- A. 0
- B. 1
- C. 1
Explanation: For saturated vapor, the entire feed is vapor, so the liquid fraction q is zero.
Correct answer: 0- A. Heating
- B. Both B. & C.
- C. Solvent extraction
- D. Cooling
Explanation: Wax is deoiled by solvent crystallisation: the wax-oil mixture is dissolved in a solvent, cooled to crystallise wax, and then separated.
Correct answer: Both B. & C.- A. 5
- B. 15
- C. 40
- D. 60
Explanation: Wax sweating works best when the oil content is not excessive, because retained oil interferes with separation during controlled heating.
Correct answer: 40- A. Perforated plate
- B. Packed bed
- C. Fluidised bed
- D. Bubble-cap
Explanation: Bubble-cap trays provide good vapour-liquid contact and tolerate changes in liquid and vapour rates, making them a traditional choice for…
Correct answer: Bubble-cap- A. 30-80
- B. 5-10
- C. 150-250
- D. 350-400
Explanation: Vacuum crude distillation commonly operates at about 30–80 mm Hg absolute to lower boiling temperatures and prevent thermal cracking of…
Correct answer: 30-80