22. Which of the following is not considered among the three best-known theories of interphase mass transfer?
A.two-film theory
B.penetration theory
C.surface renewal theory
D.Calderbank and Moo-Young theory

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23. Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system?
A.Addition of antifoams
B.Increase in temperature
C.Increase in stirrer speed
D.Both (a) and (b)

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24. At 25°C, the saturation concentration of oxygen in water is 1.26 mmol/l and the partial pressure of oxygen is 1 atm. The Henry's law constant will be
A.0.793atml/mmol
B.0.207atml/mmol
C.1.26 atml/mmol
D.8.74 atml/mmol

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25. Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the
A.superficial gas velocity
B.power consumption
C.Both (a) and (b)
D.gas concentration

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26. Turbine impeller consists of flat impeller blades with
A.a vertical pitch welded directly to the shaft
B.a angled pitch welded directly to the shaft
C.a vertical pitch welded to a horizontal disk
D.a angled pitch welded to a horizontal disk

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27. An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it
A.enhances bubble coalescence
B.causes bubbles to expand
C.discourages bubble coalescence
D.increases the surface tension of the liquid

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28. 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

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