Mechanical Operations for Chemical Engineers Questions - Set 05 - ObjectiveBooks

Mechanical Operations for Chemical Engineers Questions - Set 05

Practice Test: Question Set - 05

1. Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are
    (A) Carbonates
    (B) Sulphates
    (C) Silicates & phosphates
    (D) Bi-carbonates

2. The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be
    (A) 0.5 Wi
    (B) Wi
    (C) 1.34 Wi
    (D) 3.34 Wi

3. Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the receiving opening, cm S = greater width of the discharge opening, cm).
    (A) 0.01 L.S
    (B) 0.087 L.S
    (C) L.S
    (D) L.S/0.087

4. Which of the following oxides is not present in hematite iron ore?
    (A) Titanium oxide
    (B) Calcium oxide
    (C) Cobalt oxide
    (D) Manganese oxide

5. Mixing mechanism employed in a pan mixer is by
    (A) Mulling
    (B) Kneading
    (C) Dispersion
    (D) None of these

6. In filtration, the use of 'filter aid' helps in
    (A) Reducing the filtration pressure
    (B) Accelerating the rate of filtration
    (C) Deplugging the filter medium
    (D) Enhancing the cake porosity in case of a dense impermeable cake

7. Length/diameter ratio of a ball mill is
    (A) 1.5
    (B) 1
    (C) < 1
    (D) > 1

8. Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator?
    (A) Cresylic acid
    (B) Copper sulphate
    (C) Calcium carbonate
    (D) Sodium carbonate

9. Which one is a filter aid?
    (A) Canvas fabric
    (B) Diatomaceous earth
    (C) Calcined lime
    (D) None of these

10. The filtrate flow rate in constant pressure filtration
    (A) Continuously increases
    (B) Continuously decreases
    (C) Remain constant throughout
    (D) May increase or decrease; depends on the pressure

11. Pick out the wrong statement.
    (A) Cumulative analysis for determining surface area is preferred over differential analysis, because of the assumption that "all particles in a simple fraction equal in size" is not needed for cumulative analysis unlike differential analysis
    (B) A gate diagram is a plot of cumulative percent by weight undersize vs. the reciprocal of diameter, in which the area beneath the curve represents the surface
    (C) Capacity of crusher in choke feeding is increased
    (D) Rolling of pebbles/balls from top to bottom of the heap in tumbling mills is called 'cascading and throwing of the balls through the air to the toe of the heap is called 'cataracting'

12. In case of a ball mill,
    (A) Coarse feed requires a larger ball
    (B) Fine feed requires a larger ball
    (C) Operating speed should be more than the critical speed
    (D) None of these

13. Shell and leaf filter as compared to plate and frame filter
    (A) Entails less labor cost
    (B) Facilitates filtration under higher pressure
    (C) Provides more effective washing
    (D) All (a), (b) & (c)

14. Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the
    (A) Coagulation
    (B) Flocculation
    (C) Sedimentation
    (D) Clarification

15. A propeller agitator
    (A) Produces mainly axial flow
    (B) Is used for mixing high viscosity pastes
    (C) Runs at very slow speed (2 rpm)
    (D) All (a), (b) and (c)

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