Free Mass Transfer Operations MCQs with Answers
669 Mass Transfer Operations MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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669 questions · page 29 of 34
- A. End of falling
- B. Beginning of constant
- C. Beginning of falling
- D. None of these
Explanation: At the critical moisture content, the constant-rate period ends and the falling-rate period begins.
Correct answer: Beginning of falling- A. √T
- B. T
- C. T3
- D. T2
Explanation: In a diffusion-controlled falling-rate period, the drying time follows the characteristic diffusion time, which varies as length squared.
Correct answer: T2- A. Temperature
- B. Composition
- C. Total pressure
- D. All A., B. and C.
Explanation: Dew point is determined by vapour composition and total pressure, not by the mixture's present temperature.
Correct answer: Temperature- A. Reflux ratio
- B. Thermal condition of the feed
- C. Plate efficiency to be achieved
- D. Relative volatility
Explanation: The q-line represents the feed condition, and its slope is q/(q−1). Thus, the slope is fixed by the feed's thermal condition, such as…
Correct answer: Thermal condition of the feed- A. Concentrated solutions
- B. Gaseous solutions at high pressure
- C. Dilute solutions, over a small concentration range
- D. None of these
Explanation: The Freundlich equation is an empirical adsorption relation that is most useful for dilute solutions over a limited concentration range.
Correct answer: Dilute solutions, over a small concentration range- A. M(Xo - XF)
- B. M(Xo/XF)
- C. M ln(Xo/XF)
- D. MXo ln(Xo/XF)
Explanation: With the critical moisture equal to Xo, the falling-rate drying rate is Rc(X/Xo).
Correct answer: MXo ln(Xo/XF)- A. Multi-component distillation
- B. Gas absorption with chemical reaction
- C. Gas absorption without chemical reaction
- D. Binary distillation
Explanation: The Hatta number compares the rate of a chemical reaction in the liquid film with the rate of diffusion through that film.
Correct answer: Gas absorption with chemical reaction- A. Use steam distillation
- B. Use molecular distillation
- C. An azeotrope may be formed during distillation
- D. Use high pressure distillation
Explanation: A low relative volatility means the components have similar vapour pressures and are difficult to separate by ordinary distillation; such…
Correct answer: An azeotrope may be formed during distillation- A. Continuous
- B. Steam
- C. Flash
- D. Differential
Explanation: Rayleigh's equation describes differential or batch distillation, where the still liquid composition changes continuously as vapour is…
Correct answer: Differential- A. None of these
- B. Increases
- C. Remains unchanged
- D. Decreases
Explanation: For most liquid-liquid extraction systems, increasing temperature increases mutual solubility and shrinks the two-phase region enclosed by…
Correct answer: Decreases571. Plate efficiency in a distillation column is reduced due to the ______________________ of liquid?
- A. All A., B. & C.
- B. Foaming
- C. Weeping & dumping
- D. Entrainment
Explanation: Entrainment, foaming, and weeping or dumping all cause poor vapour-liquid contact or bypassing on trays.
Correct answer: All A., B. & C.- A. 25
- B. > 25
- C. < 25
- D. - 25
Explanation: Heating at constant pressure while keeping the humidity ratio fixed raises the corresponding adiabatic saturation, or wet-bulb…
Correct answer: > 25- A. transfer operations.
- B. Sherwood number in mass transfer is analogous to Nusselt number in heat transfer
- C. Prandtl number in heat transfer is analogous to Schmidt number in mass transfer
- D. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer
- E. Reynolds number remains the same in both heat and mass transfer
Explanation: The usual analogies are Sherwood to Nusselt, Schmidt to Prandtl, and Reynolds to Reynolds.
Correct answer: Reynolds number in mass transfer is analogous to Grashoff number in heat transfer- A. Azeotropic
- B. Extractive
- C. Steam
- D. Molecular
Explanation: Ethanol and water form an azeotrope, so ordinary fractional distillation cannot achieve complete dehydration.
Correct answer: Azeotropic- A. Ponchon-Savarit method
- B. Tray to tray calculations
- C. Enthalpy concentration method
- D. McCabe-Thiele method
Explanation: Multicomponent distillation requires component-by-component material balances and equilibrium calculations from tray to tray.
Correct answer: Tray to tray calculations- A. Sieve-plate column
- B. Bubble-cap plate column
- C. Packed tower
- D. Wetted wall column
Explanation: Packing breaks the liquid into a thin film over a large wetted area, providing greater vapour-liquid contact area than ordinary trays or a…
Correct answer: Packed tower- A. Schmidt number
- B. Sherwood number
- C. Lewis relationship
- D. Froude number
Explanation: The Schmidt and Sherwood numbers are directly associated with mass-transfer diffusion and convection, and the Lewis relationship connects…
Correct answer: Froude number- A. All A , B & C.
- B. Increasing the rate of extraction
- C. Maintaining the concentration difference between the two phases
- D. Reducing the axial mixing
Explanation: Baffles and horizontal plates suppress axial mixing, promote repeated contact between the phases, and help preserve the concentration…
Correct answer: All A , B & C.- A. Continuous
- B. Steam
- C. Azeotropic
- D. None of these
Explanation: Steam distillation is suitable for high-boiling, heat-sensitive materials because steam lowers the mixture’s boiling temperature, allowing…
Correct answer: Steam580. Mechanism of moisture removal in case of freeze drying of food stuff is by ___________________?
- A. Evaporation
- B. Adsorption
- C. Dehydration
- D. Sublimation
Explanation: In freeze drying, water is first frozen and then removed under vacuum by direct conversion of ice to vapour.
Correct answer: Sublimation