All Free Chemical Engineering MCQs with Answers

• A. 0.1 to 0.25
• B. 0.3 to 0.5
• C. 0.5 to 0.6
• D. 0.65 to 0.80

Explanation: For high-viscosity mixing, a multiple-blade paddle is broad enough to move paste effectively, with blade width commonly about 10 to 25% of…

• A. Called tube pitch
• B. Called tube clearance
• C. More in case of triangular pitch as compared to square pitch of tube layout
• D. None of these

Explanation: Tube clearance is the shortest gap between the outside surfaces of adjacent tubes, whereas tube pitch is measured from the centre of one…

• A. Increases
• B. Remain unaffected
• C. Decreases
• D. None of these

Explanation: A higher gas-to-cloth ratio means more gas passes through each unit area of filter cloth, so less cloth area and a smaller, cheaper filter…

• A. Much more than that for fully open globe valves
• B. Much less (say 2% than that for fully open globe valves)
• C. Around 7
• D. Both B. and C.

Explanation: A fully open gate valve offers very little flow resistance, with an equivalent length-to-diameter ratio of roughly 7, far below that of a…

• A. 50-75
• B. 25-50
• C. 200-250
• D. 750-1000

Explanation: Flooding in a packed tower is commonly associated with a sharp rise in pressure drop, typically about 50–75 mm water column per metre of…

• A. 500-1500
• B. 5-10
• C. 50-150
• D. 1500-2500

Explanation: Bag filters normally operate with a pressure drop of roughly 50–150 mm water gauge, which increases as dust accumulates on the filter…

• A. 10
• B. 25
• C. 75
• D. 300

Explanation: A fully open globe valve has a large resistance because the flow changes direction and passes through a restricted, tortuous passage.

• A. Less
• B. More
• C. Same
• D. Either A. or B.; depends upon the I.D. of the pipe

Explanation: For the same nominal pipe size, schedule 80 has a greater wall thickness and smaller internal diameter than schedule 40.

• A. Absorbing the contraction/expansion of pipeline due to temperature changes
• B. Prevention of fluid leakage around moving parts
• C. Facilitating smooth opening and closing of a valve
• D. Reducing the resistance of fluid flow

Explanation: A stuffing box surrounds a moving valve stem or shaft and uses packing to restrict leakage along the moving part.

• A. (1.2)3/2
• B. (1.2)3/5
• C. (1.2)5/3
• D. (1.2)2/3

Explanation: In fully turbulent mixing, power varies as N³D⁵ when the power number is constant.

• A. f = 16/NRe
• B. 5
• C. f = 0.22 NRe
• D. f = 0.04/(NRe)0.16
• E. f = 25/NRe

Explanation: For turbulent flow in a hydraulically smooth or new pipe, an empirical relation is f ≈ 0.04/Re⁰·¹⁶, with the exact coefficient depending…

• A. Both A. & B.
• B. Lowest surface area requirement for a given volume
• C. Higher structural strength
• D. None of these

Explanation: A circular section provides high structural strength because pressure stresses are distributed uniformly, and it also gives the least wall…

• A. Low viscosity liquids (< 200 poise)
• B. Large diameter tanks
• C. High viscosity liquids (> 600 poise)
• D. None of these

Explanation: Baffles are mainly needed to prevent swirling and improve mixing in low-viscosity liquids.

• A. Waste steam
• B. Destroy itself of acceleration wear due to rapid recycling
• C. None of these
• D. Back up condensate and cause water hammer in steam line

Explanation: An undersized steam trap cannot discharge condensate at the required rate, so condensate accumulates in the line.

• A. 5 to 10
• B. 55 to 75
• C. 40 to 50
• D. 15 to 30

Explanation: A propeller is a small-diameter, high-speed agitator, typically about 15 to 30% of the tank diameter.

• A. 0.1-0.12
• B. 0.4-0.5
• C. 0.45-0.6
• D. 0.2-0.45

Explanation: Tank baffles are commonly sized with a width of approximately 0.1 to 0.12 times the tank diameter.

• A. 1 to 5
• B. 20 to 100
• C. 500 to 750
• D. 1000 to 2000

Explanation: Paddle agitators are large, slow-speed impellers used mainly for blending and gentle mixing, typically operating around 20 to 100 rpm.

• A. Increase or decrease depending on the nature of the dust
• B. Decrease
• C. Remain unaffected
• D. Increase

Explanation: For a fixed particle size, a higher cyclone pressure drop usually means higher gas inlet velocity, which increases centrifugal force and…

• A. 0.3 to 0.5 d
• B. 0.1 to 0.2 d
• C. 0.65 to 0.85 d
• D. 0.95 d

Explanation: A turbine agitator generally has an impeller diameter around 0.3 to 0.5 times the tank diameter.

• A. A/P
• B. 4 A/P
• C. 4 P/A
• D. √A

Explanation: For a non-circular channel, the hydraulic or equivalent diameter is defined as D_e = 4A/P, where P is the wetted perimeter.