31. Power number is the ratio of

A. imposed forced to the inertial force
B. buoyant force to inertial force
C. gravitation force to inertial force
D. imposed force to gravitational force

32. The volume of liquid (V_L) in a cylindrical reactor can be calculated from the liquid height (H_L) and tank diameter (D_t) using the following equation

A. V_L= 4/3 x π x H_Lx D_t³/8
B. V_L= H_Lx π x D_t²/4
C. V_L= H_Lx π x D_t²
D. V_L = 4 x π x D_t²

33. The average fractional gas hold up (H) can be given as (where Z_f and Z_l are the level of aerated and clear liquid respectively)

A. H = (Z_f–Z_l)/Z_f 
B. H = Z_f /Z_l
C. H = Z_f /Z_f Z_l
D. H =(Z_f+Z_l)/Z_f

34. Which of the following(s) is/are non-mechanically agitated reactors?

A. Stirrer tank reactor
B. Bubble column
C. Airlift reactor
D. Both (b) and (c)

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