29. 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

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30. 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

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31. 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

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32. The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dt) using the following equation
A.VL = 4/3 x π x HL x Dt3/8
B.VL= HL x π x Dt2/4
C.VL= HL x π x Dt2
D.VL = 4 x π x Dt2

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33. The average fractional gas hold up (H) can be given as (where Zf and Zl are the level of aerated and clear liquid respectively)
A.H = (Zf-Zl)/Zf
B.H = Zf/Zl
C.H = Zf/ZfZl
D.H =(Zf+Zl)/Zf

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34.  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)

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35. 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

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