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 18 of 34
- A. K ∝ D2
- B. K ∝√D
- C. K ∝ D1.5
- D. K ∝ D
Explanation: Film theory gives the mass-transfer coefficient as approximately diffusivity divided by film thickness, K ≈ D/δ.
Correct answer: K ∝ D- A. Maintaining high critical humidity
- B. Both A. and C.
- C. Coating the product with inert material
- D. Maintaining low critical humidity
Explanation: Caking is reduced by keeping the product environment below the critical humidity and by coating crystals with an inert material.
Correct answer: Both A. and C.- A. Only one component
- B. Two components
- C. Any number of components
- D. Only saturated liquid
Explanation: A distillation overhead is generally a mixture whose composition depends on volatility and operating conditions; it is not restricted to…
Correct answer: Any number of components- A. Ammonia in water
- B. Benzol present in coke oven gas by wash oil
- C. All A., B. and C.
- D. SO2 in alkaline solution
Explanation: SO₂ reacts with alkaline absorbents, such as caustic or carbonate solutions, so its absorption is enhanced by chemical reaction.
Correct answer: SO2 in alkaline solution- A. S1/S2
- B. S2/S1
- C. S1 - S2
- D. S1 × S2
Explanation: The absorption factor is A = L/(mG), which is the operating-line slope divided by the equilibrium-line slope when these are written on the…
Correct answer: S1/S2- A. Spray dryer
- B. Spouted bed dryer
- C. Tunnel dryer
- D. Pan open to atmosphere
Explanation: A detergent solution is atomized into a stream of hot air, giving rapid evaporation and powder formation in a spray dryer.
Correct answer: Spray dryer- A. 0.60
- B. 0.24
- C. 1
- D. 0.72
Explanation: For the air-water vapour system, the heat and mass transfer coefficients are related through the Lewis relation, whose practical value is…
Correct answer: 1- A. Increase both 'G' and 'S'
- B. Decrease both 'G' and 'S'
- C. Increase 'G' and decrease 'S'
- D. Increase 'S' and decrease 'G'
Explanation: The absorption factor is proportional to solvent flow and inversely proportional to gas flow, A = S/(mG).
Correct answer: Increase 'S' and decrease 'G'- A. Pachuka tank
- B. Agitated vessels
- C. Centrifugal extractors
- D. Packed towers
Explanation: A Pachuca tank is mainly used for agitation and gas-assisted leaching of solids, not liquid-liquid extraction.
Correct answer: Pachuka tank- A. Pressure rises
- B. Temperature rises
- C. Temperature falls
- D. Pressure falls
Explanation: When temperature rises, the saturation vapour pressure increases, so the same or even greater moisture content represents a smaller…
Correct answer: Temperature rises- A. Flow rate of inlet air
- B. Relative humidity of outlet air
- C. Temperature of the solid
- D. Humidity of inlet air
Explanation: Case hardening results when the surface dries and hardens too quickly, restricting internal moisture movement.
Correct answer: Temperature of the solid- A. Increases
- B. May increase or decrease; depends on the type of adsorbate
- C. Remains unchanged
- D. Decreases
Explanation: The highest-energy adsorption sites are occupied first, so the heat released per additional amount adsorbed generally falls as adsorbate…
Correct answer: Decreases- A. Higher relative humidity
- B. Higher absolute (specific) humidity
- C. Higher dew point
- D. Higher wet bulb temperature
Explanation: Cooling unsaturated air at constant pressure leaves its humidity ratio nearly unchanged until saturation, while the saturation capacity…
Correct answer: Higher relative humidity- A. 9.21
- B. 4.605
- C. 100
- D. 0.001
Explanation: For irreversible reaction absorption, the gas-phase transfer-unit calculation reduces to the logarithmic concentration ratio: NOG =…
Correct answer: 4.605- A. Sieve plate
- B. Pulse
- C. Bubble cap
- D. Packed
Explanation: In a packed column, gas forms the continuous phase while liquid spreads over the packing as a dispersed film.
Correct answer: Packed- A. Both A. & B.
- B. Above
- C. Across
- D. Neither A. nor B.
Explanation: Maximum plate efficiency requires ideal contacting both in the liquid flow across the plate and in the vapour-liquid contact zone above…
Correct answer: Both A. & B.- A. Viscosity
- B. Solubility
- C. Density
- D. Relative volatility
Explanation: Selective absorption separates gases according to how readily each dissolves in the solvent, that is, according to their relative…
Correct answer: Solubility- A. Results from very low gas velocity
- B. Is desirable from point efficiency consideration
- C. Is characterised by the presence of foam throughout the space between trays
- D. Reduces the overall pressure drop
Explanation: Priming occurs when vapour velocity becomes excessive, causing liquid to be carried upward and foam to fill the space between trays.
Correct answer: Is characterised by the presence of foam throughout the space between trays- A. Raising the temperature
- B. Lowering the total pressure
- C. Neither A. nor B.
- D. Both A. and B.
Explanation: Steam consumption per unit distillate falls when the organic component contributes a larger share of the total vapour pressure.
Correct answer: Both A. and B.- A. Gas
- B. Room
- C. Wet bulb
- D. None of these
Explanation: A saturated gas is already at its dew point, so cooling is just about to cause condensation.
Correct answer: Gas