Free Mass Transfer Operations MCQs with Answers

• A. 0
• B. > 1
• C. 1
• D. < 1

Explanation: Distillation requires unequal volatilities, and relative volatility is conventionally defined as the volatility of the more volatile…

• A. (1 + X)/X
• B. X/(1 - X)
• C. X/(X + 1)
• D. (1 - X)/X

Explanation: On a dry basis, X equals the mass of moisture divided by the mass of dry solid.

• A. Ri = Re/(1 - Re)
• B. Ri = (1 - Re)/Re
• C. Ri = Re
• D. Ri = Re/(1 + Re)

Explanation: With an external reflux ratio Re = L/D and an internal reflux ratio Ri = L/V, the total condenser balance gives V = L + D.

• A. Absorption
• B. Liquid extraction
• C. Fractional crystallisation
• D. Evaporation

Explanation: Absorption transfers a solute from a gas into a liquid, so it is not the usual operation for separating components already present in a…

• A. Increases
• B. Remains same
• C. Decreases
• D. Either A. or B., depends on the system

Explanation: For ordinary binary vapour-liquid systems, increasing pressure brings the component K-values closer together, so their ratio, the relative…

• A. Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor
• B. Door classifier can be used for leaching of coarse solids
• C. Fine solids cannot be leached in a Pachuca tank
• D. Very high temperature is not needed for the leaching of sugar beet

Explanation: A Pachuca tank is a slurry leacher that can handle fine solids, so saying that fine solids cannot be leached in it is wrong.

• A. Activated clay
• B. Wood charcoal
• C. Silica gel
• D. Bone charcoal

Explanation: Bone charcoal, also called bone black, adsorbs colouring matter and impurities from raw sugar syrup, giving refined sugar its lighter…

• A. Both B. and C.
• B. Maldistribution of liquid
• C. Non-uniformity of packing
• D. High pressure drop

Explanation: Channeling occurs when liquid follows preferred paths instead of wetting the entire packing bed.

• A. 1
• B. > 1
• C. < 1
• D. 0.5

Explanation: Relative volatility greater than one indicates that the more volatile component is enriched in the vapour phase, making separation…

• A. Enthalpy balance only
• B. Material balance only
• C. Both enthalpy and material balances
• D. The assumption of constant molal-overflow

Explanation: The Ponchon-Savarit method uses enthalpy-composition diagrams, so it simultaneously applies component material balances and total enthalpy…

• A. Liquid hold up
• B. Gas viscosity
• C. Liquid density
• D. Flooding

Explanation: The diameter of a packed column is governed mainly by the allowable gas velocity before flooding occurs.

• A. Increases in winter
• B. Decreases in winter
• C. Increases in summer
• D. None of these

Explanation: An unlagged column loses more heat during winter, reducing useful internal vapour and liquid traffic.

• A. Form a new azeotrope of low relative volatility with one of the constituents of the mixture
• B. Form a low boiling azeotrope with one of the constituents of the mixture
• C. Have high latent heat of vaporisation
• D. Have high viscosity to provide high tray efficiency

Explanation: An effective entrainer forms a low-boiling azeotrope with one component, allowing that component to be removed overhead and breaking the…

• A. Bubble-cap column
• B. Sieve-plate column
• C. Packed column (stacked)
• D. Randomly packed column

Explanation: Stacked or structured packing offers a relatively open, orderly flow path, so it produces less friction and pressure drop per unit height…

• A. Sensible heat changes are negligible compared with latent heat changes
• B. Molar latent heats of all components are equal
• C. Heat of mixing is negligible
• D. None of these

Explanation: The McCabe-Thiele method uses constant molar overflow, which assumes negligible sensible-heat and heat-of-mixing effects and approximately…

• A. None of these
• B. Methyl alcohol-acetone
• C. Butyl acetate-water
• D. Water-alcohol

Explanation: Water-ethanol, methanol-acetone, and butyl acetate-water are known azeotropic systems at atmospheric pressure, with the last commonly…

• A. Ammonia from coke oven gas using refrigerated water
• B. Benzol from coke oven gas using solar oil/wash oil
• C. Carbon dioxide from gaseous stream using alkaline solution
• D. Tar from coke oven gas in primary gas coolers using chilled water

Explanation: Carbon dioxide reacts with alkaline absorbents such as sodium hydroxide or potassium carbonate, so its removal combines absorption with a…

• A. Pulse column
• B. Packed column (with dumped packing)
• C. Bubble plate column
• D. Packed column (with stacked packing)

Explanation: Stacked packing has a more regular structure and lower resistance to gas flow than dumped packing, while bubble-plate and pulse columns…

• A. Centrifugal
• B. Packed
• C. Plate
• D. None of these

Explanation: Penicillin is temperature-sensitive and is commonly extracted using a centrifugal extractor, which provides rapid liquid-liquid contact…

• A. Always higher than
• B. Always lower than
• C. Same as
• D. Dependent on the system; can be either lower or higher than

Explanation: In the usual adsorption hysteresis associated with capillary condensation, the desorption branch occurs at a lower equilibrium pressure…