All Free Chemical Engineering MCQs with Answers

• A. Synthetic zeolites crystals/metal alumino-silicates
• B. Silica
• C. Alumina
• D. None of these

Explanation: Molecular sieves are crystalline synthetic zeolites made from metal aluminosilicates.

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: At the plait point, the compositions of the two liquid phases become identical and the tie-line length becomes zero.

• A. Nsc = 2
• B. Nst = 2
• C. Nsh = 2
• D. None of these

Explanation: For a spherical drop transferring mass by molecular diffusion into stagnant surroundings, the limiting Sherwood number is 2.

• A. Both A. & B.
• B. Parallel
• C. Straight
• D. Neither A. nor B.

Explanation: Equality of overall and Murphree efficiencies follows when the graphical stage relationships do not change from tray to tray.

• A. p >>P
• B. p = P
• C. p < P
• D. p << P

Explanation: Condensation starts when the vapour partial pressure reaches the saturation vapour pressure of the liquid at the same temperature.

• A. Molal diffusivity
• B. Volumetric co-efficient
• C. Mass transfer co-efficient
• D. None of these

Explanation: A wetted-wall tower provides a known contact area between the phases, allowing the mass-transfer coefficient to be determined from…

• A. Yes
• B. Yes; but the air flow rate should be excessively high
• C. Yes; but height of cooling tower will be prohibitively high
• D. No

Explanation: In a cooling tower, the lowest practical water temperature is limited by the entering air wet-bulb temperature.

• A. 0.25
• B. 2.5
• C. 1.25
• D. 0.0025

Explanation: The diffusivity of water vapour in air near room temperature is approximately 0.25 cm²/s.

• A. Condenser and reboiler loads are the same in both the cases
• B. Both condenser and reboiler loads are higher in case (ii) as compared to case (i)
• C. Condenser load is the same in both the cases but reboiler load is higher in case (ii)
• D. Reboiler load is the same in both the cases but condenser load is higher in case (ii)

Explanation: Subcooled reflux must first be heated to its bubble point, increasing the reboiler duty, while the condenser must remove extra sensible…

• A. Recovery of tannis from the tree barks and woods
• B. Leaching sodium nitrate from Chilean nitrate bearing rock
• C. Both A. and B.
• D. Neither A. nor B.

Explanation: The Shanks system is a countercurrent multiple-contact leaching process used for extracting tannins from bark and wood and for leaching…

• A. Multiple effect evaporator
• B. Rotating disc contactor
• C. Rotary dryer
• D. Mechanical draft cooling tower

Explanation: A drift eliminator is fitted in a cooling tower to remove entrained water droplets from the leaving air and reduce water loss.

• A. Cold water leaving the tower and the wet bulb temperature of the surrounding air
• B. Hot water entering the tower and the wet bulb temperature of the surrounding air
• C. Hot water entering and the cooled water leaving the cooling tower
• D. None of these

Explanation: Cooling-tower approach is the temperature difference between the cooled water leaving the tower and the entering air wet-bulb temperature.

• A. Inverse
• B. Linear
• C. Exponential
• D. Logarithmic

Explanation: At fixed temperature and pressure, humid volume is proportional to the amount of water vapour present, represented by humidity.

• A. Less than
• B. Same as
• C. More than
• D. Very much less

Explanation: Flooding begins when the tray pressure drop exceeds the liquid head available in the downcomer, preventing liquid from flowing downward…

• A. Low vapor pressure
• B. Low viscosity
• C. None of these
• D. High gas solubility

Explanation: A good absorption solvent should have low vapour pressure and viscosity and high solubility for the absorbed gas.

• A. Data insufficient, can't be predicted
• B. Decrease
• C. Remain same
• D. Increase

Explanation: Raising pressure generally lowers relative volatility for distillation systems, making separation more difficult.

• A. Condenser and reboiler surfaces
• B. Area between operating line and 45° diagonal x-y diagram
• C. Tower cross-section
• D. None of these

Explanation: Increasing reflux moves the operating line closer to the 45° diagonal, so the area between them does not increase.

• A. Enthalpy concentration method
• B. Ponchan-Savarit method
• C. McCabe-Thiele method
• D. Plate absorption column

Explanation: The McCabe-Thiele method uses the constant-molal-overflow assumption, allowing straight operating lines to be drawn on the x-y diagram.

• A. At very high liquid flow rate
• B. In towers packed randomly with crushed solids
• C. In dumped packing of regular units
• D. In towers packed with stacked packing

Explanation: Stacked packing tends to create preferential channels and poor liquid redistribution because the elements are arranged in continuous…

• A. Vapour pressure of component A to that of component B
• B. Vapour pressure of component A to the total pressure
• C. Vapour pressure of component A to the partial pressure of A
• D. Partial pressure of component A to the total pressure

Explanation: For an ideal liquid and vapour, Raoult's and Dalton's laws give relative volatility as \(\alpha=P_A^{sat}/P_B^{sat}\), the ratio of the…