200 Best MCQs on Agitation and aeration- biochemical engineering
Q25). Vortexing in stirred tank reactors can be prevented by
a).installing baffles in the reactor
b).shifting the impeller to an off-centre position
c).Both (a) and (b)
d).using axial flow impellers
Correct Answer:
Both (a) and (b)
Explaination:
Q26). Which of the following would be best described as an axial flow impeller?
a).An impeller with blades pitched at 45° to the vertical
b).An impeller which directs liquid flow towards the base of the reactor
c).Both (a) and (b)
d).An impeller with blades pitched at 75° to the vertical
Correct Answer:
Both (a) and (b)
Explaination:
Q27). Henry’s law relates
a).the partial pressure of oxygen and the saturation concentration of oxygen in the liquid
b).the oxygen transfer rate and the bubble size
c).the oxygen transfer rate and the temperature
d).the oxygen transfer rate to the partial pressure of oxygen in the liquid
Correct Answer:
the partial pressure of oxygen and the saturation concentration of oxygen in the liquid
Explaination:
Q28). Power number is ratio of
a).imposed forced to intertial force
b).bouyant force to inertial force
c).gravitation force to inertial force
d).imposed force to gravitational force
Correct Answer:
imposed forced to intertial force
Explaination:
Q29). Which of the following(s) is/are non-mechanically agitated reactors?
a).Stirrer tank reactor
b).Bubble column
c).Air lift reactor
d).Both (b) and (c)
Correct Answer:
Both (b) and (c)
Explaination:
Q30). Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions?
a).Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor
b).Crystals and precipitates are thoroughly broken down, so as to ensure easy separation of the solids from the mother liquor
c).Both (a) and (b)
d).Axial flow impellers provide low shear, energy efficient mixing conditions
Correct Answer:
Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor
Explaination:
Q31). Which of the following will have the highest surface area available for oxygen transfer?
a).A shake flask
b).A standing test tube
c).A non-sparged stirred tank reactor agitated at 400 rpm
d).A sparged stirred tank reactor agitated at 400 rpm
Correct Answer:
A sparged stirred tank reactor agitated at 400 rpm
Explaination:
Q32). A flooded impeller will lead to poor oxygen transfer rates because
a).bubbles tend to coalesce under the impeller
b).bubbles tend to break down too rapidly under high shear conditions
c).bubbles tend to move too quickly through the bulk liquid
d).the cells clog up the surface of the bubble
Correct Answer:
bubbles tend to coalesce under the impeller
Explaination: