Questions and answers for exam Preparation

MCQs

Total Questions : 234 | Page 7 of 24 pages

Question 61. Which of the following number is calculated from the diameter and peripheral speed of the impeller?

Reynolds number
Froude number
Power number
None of these

Discuss Question

Answer: Option A. -> Reynolds number
Answer: (a).Reynolds number

Question 62. 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

0.793atml/mmol
0.207atml/mmol
1.26 atml/mmol
8.74 atml/mmol

Discuss Question

Answer: Option A. -> 0.793atml/mmol
Answer: (a).0.793atml/mmol

Question 63. Which of the following is not considered among the three best-known theories of interphase mass transfer?

two-film theory
penetration theory
surface renewal theory
Calderbank and Moo-Young theory

Discuss Question

Answer: Option D. -> Calderbank and Moo-Young theory
Answer: (d).Calderbank and Moo-Young theory

Question 64. The reason of using a flat disk in a Turbine is

to create high shear conditions
to break up bubbles more efficiently than the impeller blades
to ensure that the bulk of the energy consumption occurs at the blades
all of the above

Discuss Question

Answer: Option C. -> to ensure that the bulk of the energy consumption occurs at the blades
Answer: (c).to ensure that the bulk of the energy consumption occurs at the blades

Question 65. Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system?

Addition of antifoams
Increase in temperature
Increase in stirrer speed
Both (a) and (b)

Discuss Question

Answer: Option C. -> Increase in stirrer speed
Answer: (c).Increase in stirrer speed

Question 66. Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the

superficial gas velocity
power consumption
Both (a) and (b)
gas concentration

Discuss Question

Answer: Option C. -> Both (a) and (b)
Answer: (c).Both (a) and (b)

Question 67. For turbulent flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei, is Reynolds number for agitator; Di, stirrer diameter and N, stirrer speed)

Np = K(Rei)¹
Np = N2Di(Rei)¹
Np = K
Can't be correlated

Discuss Question

Answer: Option C. -> Np = K
Answer: (c).Np = K

Question 68. In a two-phase system where the continuous phase remains in place, the gas hold up can be expressed as (where Vs and Vt are the superficial gas velocity and bubble rise velocity)

H = Vs/(Vs-Vt)
H = Vs/(Vs+ Vt)
H = Vs/(Vs.Vt)
H = (Vs+Vt)/Vs

Discuss Question

Answer: Option B. -> H = Vs/(Vs+ Vt)
Answer: (b).H = Vs/(Vs+ Vt)

Question 69. What is the effect of the concentration of dissolved salts and sugars on the oxygen transfer rate?

The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
The KLa of the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
The KLa of the medium increases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
None of the above

Discuss Question

Answer: Option A. -> The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
Answer: (a).The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate

Question 70. In a bioreactor, if at a particular time the oxygen transfer rate is 23 kg.h¹, then the oxygen uptake will be