200 Best MCQs on Agitation and aeration- biochemical engineering

Q41). Pure oxygen, if used instead of air will increase oxygen transfer rates because

a).the saturation concentration of oxygen is higher
b).the bubble size is smaller
c).the oxygen transfer coefficient is larger
d).the partial pressure of oxygen in the gas phase is lower

Correct Answer:
the saturation concentration of oxygen is higher
Explaination:

Q42). The Intermig impeller is

a).an axial flow impeller which can be used for the culture of aerobic organisms
b).directed upwards rather than towards the base of the reactor
c).a fork shaped extensions to the impeller facilitate bubble break up
d).All of the above

Correct Answer:
All of the above
Explaination:

Q43). Main reason for using baffles in stirred tank reactors are

a).baffles permit turbulence conditions to arise at low stirrer speed
b).baffles will allow axial mixing to occur even with radial flow impellers
c).both (a) and (b)
d).baffles prevent turbulent conditions in stirred tank reactors

Correct Answer:
both (a) and (b)
Explaination:

Q44). Which of the following is not classified as an axial flow impeller?

a).A propeller
b).A marine impeller
c).A Rushton turbine
d).A hydrofoil impeller

Correct Answer:
A Rushton turbine
Explaination:

Q45). Power number (Np) is also known as

a).Froude’s number
b).Bond’s number
c).Newton’s number
d).Rayleigh’s number

Correct Answer:
Newton’s number
Explaination:

Q46). Flooding is a condition/phenomenon which occur in a bioreactor when

a).The air escapes without being distributed by the agitator
b).The fermenter medium spills out the reactor due to foaming
c).The volume of foam is more than the volume of broth
d).None of the above

Correct Answer:
The air escapes without being distributed by the agitator
Explaination:

Q47). A cylindrical reactor has a liquid volume of 100,000 litres. It has an aspect ratio the ratio of the channel height to width of 1:1. The height of the liquid in the reactor will be approximately:

a).1.0 m
b).3.0 m
c).5.0 m
d).7.0 m

Correct Answer:
5.0 m
Explaination:

Q48). Detergent like substances produced by microorganisms during a fermentation will lead to

a).decrease the surface tension of the liquid
b).accumulate at the gas liquid interface
c).decrease the rate of bubble coalescence
d).all of the above

Correct Answer:
all of the above
Explaination: