Agitation and Aeration problems
- 1. Which of the following is not classified as an axial flow impeller?
Options- A. A propeller
- B. A marine impeller
- C. A Rushton turbine
- D. A hydrofoil impeller Discuss
Correct Answer: A Rushton turbine
- 2. The Intermig impeller is
Options- 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 Discuss
Correct Answer: All of the above
- 3. To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed?
Options- A. Liquid volume in the flask is reduced
- B. Stirrer speed is increased
- C. Baffled flasks are used
- D. All of the above Discuss
Correct Answer: All of the above
- 4. Industrial paddle agitators turn at the speed of
Options- A. 20 and 150 rpm
- B. 150 and 300 rpm
- C. 400 and 800 rpm
- D. 1150 rpm Discuss
Correct Answer: 20 and 150 rpm
- 5. Detergent like substances produced by microorganisms during a fermentation will lead to
Options- 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 Discuss
Correct Answer: all of the above
- 6. Which of the following stirrer requires least amount of energy for same yield?
Options- A. Mig
- B. Intermig
- C. Turbine
- D. Disc Discuss
Correct Answer: Intermig
- 7. Pure oxygen, if used instead of air will increase oxygen transfer rates because
Options- 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 Discuss
Correct Answer: the saturation concentration of oxygen is higher
- 8. A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 litres. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:
Options- A. 1.3 m
- B. 3.3 m
- C. 5.3 m
- D. 7.3 m Discuss
Correct Answer: 1.3 m
- 9. Which of the following is correct for the off-centre impellers?
Options- A. Off-centre impellers can be used with any size reactor
- B. Off-centre impellers should only be used with reactors with volumes less than 10 m3
- C. The impeller should never be placed in an off-centre position
- D. Off-centre impellers can be used when volume is greater than 10 m3 Discuss
Correct Answer: Off-centre impellers should only be used with reactors with volumes less than 10 m3
- 10. Flooding is a condition/phenomenon which occur in a bioreactor when
Options- 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 Discuss
Correct Answer: The air escapes without being distributed by the agitator
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