# Food Engineering Questions and Answers – Unit Operations – Diffusion and Mass Transfer-2

This set of Food Engineering quiz focuses on “Diffusion and Mass Transfer-2”.

1. Statement 1: Concentration is a product of diffusivity and solubility.
Statement 2: Permeability coefficient in case of food packaging can be written as product of partial pressure and solubility using Henry’s law.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: Permeability coefficient is a product of diffusivity and solubility. Concentration in case of food packaging can be written as product of partial pressure and solubility using Henry’s law.

2. The existence of a thick constant film between two phases is a proposal by which of the following theories?
a) Film theory
b) Penetration theory
c) Surface renewal theory
d) All of the mentioned

Explanation: The existence of a thick constant film between two phases is a proposal by the Film theory.

3. Statement 1: Penetration theory states that mass transfer coefficient is directly proportional to diffusivity coefficient which was later proved wrong.
Statement 2: Penetration theory states that mass transfer is based on unsteady mass transfer.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: Film theory states that mass transfer coefficient is directly proportional to diffusivity coefficient which was later proved wrong.

4. Statement 1: In film theory, mass transfer coefficient is proportional to D1/2
Statement 2: Penetration theory states that all elements are exposed at the same time which is unrealistic.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: In Penetration theory, mass transfer coefficient is proportional to D1/2 Penetration theory.

5. Which theory proposes that the film is continuously getting renewed and replaced by the bulk liquid?
a) Film theory
b) Penetration theory
c) Surface renewal theory
d) None of the mentioned

Explanation: Surface renewal theory proposes that the film is continuously getting renewed and replaced by the bulk liquid.
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6. Statement 1: KLa is measured together and not separately.
a) True
b) False

Explanation: KLa is measured together and not separately.

7. Which of the following is not a measuring technique of KLa?
a) Dynamic gassing out method
b) Static method
c) Sulphite oxidation method
d) None of the mentioned

Explanation: Dynamic gassing out method, Static method and Sulphite ore method are all measuring techniques of KLa.

8. Which of the following is also called Oxygen balancing method?
a) Dynamic gassing out method
b) Static method
c) Sulphite oxidation method
d) None of the mentioned

Explanation: Static method is also called Oxygen balancing method.

9. Sherwood number is _____
a) Product of schmidst and grashof number
b) Total mass transferred by mass transferred due to molecular diffusion
c) Product of schmidst and reynold number
d) None of the mentioned

Explanation: Sherwood number is total mass transferred by mass transferred due to molecular diffusion.

10. Rayleigh number is _____
a) Product of schmidst and grashof number
b) Total mass transferred by mass transferred due to molecular diffusion
c) Product of schmidst and reynold number
d) None of the mentioned

Explanation: Rayleigh number is a product of schmidst and grashof number.

Sanfoundry Global Education & Learning Series – Food Engineering.

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