Free Mass Transfer Operations MCQs with Answers

• A. Is used for extraction of oil from oilseed
• B. Is a static bed leaching equipment
• C. Is a centrifugal extractor
• D. Employs only counter-current extraction

Explanation: A Bollman extractor is a continuous percolation extractor widely used for recovering oil from oilseeds.

• A. Large quantity of solvent is required to extract the solute
• B. Solvent of low freezing point should be used
• C. Solvent of low latent heat of vaporisation should be used
• D. Very small quantity of solvent is required

Explanation: If the solvent has low solubility for the solute, each unit of solvent extracts only a small amount.

• A. Liquid-liquid extraction
• B. Absorption
• C. Leaching
• D. None of these

Explanation: Tea percolation passes hot water through a bed of solid tea leaves and dissolves the soluble constituents into the liquid.

• A. Baffle tower
• B. Spray column
• C. Mixer settler
• D. Pulse column

Explanation: Pulse columns have no continuously moving internal mechanical parts, making them suitable for handling highly corrosive and radioactive…

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

Explanation: For most gases, dissolution in a liquid is exothermic, so increasing temperature drives the gas out of solution and reduces its solubility…

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: The standard degree-of-freedom analysis for leaching and solvent-extraction calculations leaves three independent specifications after…

• A. Evaporation
• B. Drying
• C. Both B. and C.
• D. Crystallisation

Explanation: Urea prilling converts concentrated or molten urea into solid spherical particles by spraying it and removing heat and residual moisture.

• A. Thermal diffusivity/mass diffusivity
• B. Thermal diffusivity/momentum diffusivity
• C. Mass diffusivity/thermal diffusivity
• D. Momentum diffusivity/mass diffusivity

Explanation: The Schmidt number compares momentum diffusivity with mass diffusivity, so Sc = ν/D or μ/(ρD).

• A. Total
• B. Operating
• C. Minimum
• D. Maximum permissible

Explanation: The Fenske equation gives the minimum number of theoretical stages, which occurs at total reflux.

• A. Equal to
• B. Higher than
• C. Lower than
• D. Either A. or B., depends on the mixture composition

Explanation: For an unsaturated gas-vapour mixture, percentage saturation based on humidity is lower than relative saturation based directly on vapour…

• A. Form minimum boiling azeotrope
• B. Form constant boiling azeotrope
• C. Have very close boiling points
• D. Have very wide boiling points

Explanation: Flash distillation provides only limited separation in a single equilibrium stage, so it is most useful when the components have…

• A. Solvent extraction
• B. Distillation
• C. Absorption
• D. None of these

Explanation: In solvent extraction, selectivity measures how preferentially the solvent removes one solute over another, directly determining the…

• A. Decreases with time
• B. Does not change with time
• C. Increases with time
• D. Does not affect the moisture content of the wet solid

Explanation: During the constant-rate period, the wet surface remains effectively saturated and evaporation is controlled by external heat and mass…

• A. Remains unaffected
• B. Decreases
• C. Increases
• D. And the heat required in reboiler decreases

Explanation: A higher reflux ratio increases the liquid and vapour traffic in the column, so the condenser must remove more heat for the returning…

• A. Depend on saturated boiling point; may increase or decrease
• B. Decrease
• C. Remain same
• D. Increase

Explanation: Changing saturated vapour feed to saturated liquid feed changes the q-line from horizontal to vertical and generally makes the stripping…

• A. Steam jet ejector with a barometric condenser
• B. Compressed air jet
• C. Suction pump
• D. None of these

Explanation: Vacuum crystallisers commonly use a steam-jet ejector, with a barometric condenser to condense the entrained steam and maintain the…

• A. Fick's law
• B. Gibb's equation
• C. Freundlich equation
• D. None of these

Explanation: The Freundlich equation represents adsorption equilibrium by relating the amount adsorbed to the pressure or concentration of the…

• A. Extractive distillation
• B. Absorption
• C. Crystallisation
• D. None of these

Explanation: Adducts and clathrates are solid compounds or inclusion complexes formed during special crystallisation processes, helping separate one…

• A. Zero
• B. Hundred
• C. None of these
• D. Both zero and hundred

Explanation: Percentage humidity is lower than relative humidity because humidity ratio uses the denominator for saturated vapour, while relative…

• A. Lewis number
• B. Psychrometric ratio
• C. Sherwood number
• D. Stanton number

Explanation: The ratio Sc/Pr equals the Lewis number, since Sc measures momentum diffusivity relative to mass diffusivity and Pr measures momentum…