All Free Chemical Engineering MCQs with Answers

• A. Pressure
• B. Both A. & B.
• C. Temperature
• D. Neither A. nor B.

Explanation: Knudsen diffusivity varies approximately with the square root of absolute temperature because molecular velocities increase with…

• A. Measures the catalyst surface area directly
• B. Operates at very high pressure
• C. Is made entirely of stainless steel
• D. None of these

Explanation: BET apparatus determines specific surface area from gas adsorption data, rather than measuring the area directly.

• A. Both A. and B.
• B. Liquid hold-up
• C. Specific inter-facial area
• D. None of these

Explanation: Gas-liquid reactor performance depends strongly on the interfacial area available for transfer and on liquid hold-up, which determines…

• A. Langmuir adsorption isotherm
• B. Adsorption isobar
• C. Freundlich adsorption isotherm
• D. None of these

Explanation: An adsorption isobar shows the amount adsorbed as temperature changes at constant pressure.

• A. Increases
• B. Decreases
• C. Remains unchanged
• D. Increases exponentially

Explanation: For bulk gas diffusion, increasing pressure increases molecular collision frequency and reduces the mean free path, so the diffusivity…

• A. T
• B. T2
• C. 1/√T
• D. √T

Explanation: Knudsen diffusivity is controlled by molecular-wall collisions and varies as the mean molecular speed.

• A. He
• B. H2
• C. CO2
• D. N2

Explanation: Nitrogen adsorption is conventionally used in the BET method because N₂ has suitable size, readily forms a measurable monolayer at…

• A. Langmuir's assumption applies to every adsorbed layer
• B. (except the first one) is involved in each of the evaporation process
• C. The adsorbed layer may be polymolecular in thickness and the heat of adsorption in each layer
• D. There is no dynamic equilibrium between successive layer
• E. None of these

Explanation: BET theory assumes dynamic equilibrium between successive adsorbed layers, so the statement that no such equilibrium exists is not a BET…

• A. Sparkler
• B. Pre-coat
• C. Vacuum leaf
• D. Plate and frame

Explanation: A pre-coat of filter aid forms a porous filtering layer that prevents gelatinous solids from sealing the filter medium or plugging the…

• A. Recovery/rejection
• B. Recovery
• C. None of these
• D. Rejection

Explanation: Screen efficiency is generally the product of recovery of the wanted fraction and rejection of the unwanted fraction, not their ratio or…

• A. Stainless steel
• B. Wooden plank
• C. High speed steel
• D. Cast iron

Explanation: Plate-and-frame filter supports are conventionally made of cast iron because it provides a strong, rigid, economical support for the…

• A. Plate and flame filter
• B. Leaf filter (Moore filter)
• C. Rotary drum filter
• D. Sand filter

Explanation: A plate-and-frame filter is a pressure filter because slurry is forced through the filter cloth by applied pressure.

• A. Nylon
• B. Cotton fabric
• C. Metal cloth of monel or stainless steel
• D. Glass cloth

Explanation: Cotton fabric is unsuitable for strongly corrosive liquids because it can be chemically attacked and degraded.

• A. Agitation
• B. Filtration
• C. Size enlargement
• D. Humidification

Explanation: Humidification transfers water vapour into air and is therefore a gas-liquid mass-transfer operation, not a mechanical operation.

• A. Sand
• B. Shell & leaf
• C. Plate & frame
• D. Rotary vacuum

Explanation: A sand filter is effective for clarifying a large water flow containing only a small concentration of suspended precipitate.

• A. 0.5
• B. < 1
• C. 1
• D. √3

Explanation: Sphericity equals the surface area of an equal-volume sphere divided by the actual particle surface area, and it is 1 only for a sphere.

• A. Sodium silicate
• B. Lime
• C. Quartz
• D. Alumina

Explanation: Quartz is an inert mineral and is not normally used as a surface-active or conditioning agent in flocculation.

• A. Cresylic acid
• B. Sodium carbonate
• C. Calcium carbonate
• D. Copper sulphate

Explanation: Copper sulphate is a classic activator in froth flotation, especially for activating sphalerite so it can respond to collectors.

• A. Continuously decreases
• B. Continuously increases
• C. Remain constant throughout
• D. May increase or decrease; depends on the pressure

Explanation: At constant pressure, the growing filter cake adds resistance to flow as filtration proceeds, so the filtrate flow rate continuously…

• A. Coagulation
• B. Sedimentation
• C. Flocculation
• D. Clarification

Explanation: Sedimentation uses gravity to separate a suspension into a clear supernatant and a concentrated, denser slurry.