Food Engineering Multiple Choice Questions on “Unit Operations – Crystallization-1”.
1. Celinium Sulphate is an exception of the solubility curve. When the temperature is increased, its solubility decreases.
a) True
b) False
Answer: a
Clarification: Celinium Sulphate is an exception of the solubility curve. When the temperature is increased, its solubility decreases.
2. Which of the following is NOT an important criteria for crystal formation?
a) Caking characteristics of the crystal
b) Moisture content
c) Shape
d) None of the mentioned
Answer: d
Clarification: All the mentioned factors are important criteria for the formation of crystals.
3. Statement 1: The solubility of NaCl increases with the increase in temperature.
Statement 2: Crystal formation is hindered by nucleation taking place on the crystal surface.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: The solubility of NaCl increases with the increase in temperature. Crystal formation is hindered by nucleation taking place on the crystal surface. It should take place from within.
4. Statement 1: Solid food items containing water molecules are more soluble as the temperature increases.
Statement 2: This growth takes place in steps.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Solid food items containing water molecules are more soluble as the temperature increases. This growth takes place in steps.
5. Which of the following tells the significance of crystallization in food processing?
a) Consistency of food emulsions
b) A good feel of food inside the mouth
c) The physical stability of food
d) All of the mentioned
Answer: d
Clarification: Consistency of food emulsions, a good feel of food inside the mouth and the physical stability of food, all have a significant effect on the food processing.
6. Statement 1: Crystallization is both a mass and heat transfer operation.
Statement 2: The crystals and mother liquor obtained from a crystallizer are called _____
a) True, nucleation
b) False, solid residue
c) True, magma
d) False, crystal growth
Answer: c
Clarification: Crystallization is both a mass and heat transfer operation. The crystals and mother liquor obtained from a crystallizer are called magma.
7. Statement 1: Smaller particles dissolve as they have a larger surface area and larger particles grow.
Statement 2: The above process is called Ostwald ripening.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Smaller particles dissolve as they have a larger surface area and larger particles grow. The above process is called Ostwald ripening.
8. The ratio of concentration of a super saturated solution to a saturated solution is denoted by α’ which is stated by the Kelvin equation. How is it related to the crystal size and interfacial tension between solid and liquid?
a) Directly, indirectly
b) Indirectly, directly
c) Directly, directly
d) Indirectly, indirectly
Answer: b
Clarification: Crystal size is indirectly related to α’ and interfacial tension between solid and liquid is directly related to α’.
9. Parameters affecting crystallization are ____________
a) Agitator speed
b) Population density
c) Purity of solution
d) All of the mentioned
Answer: d
Clarification: All of the mentioned factors affect crystallization.
10. Which of the following facilitates crystallization?
a) Hot concentrated solution is cooled for crystals to form
b) Solution is concentrated by evaporation
c) Adiabatic evaporation and cooling
d) All of the mentioned
Answer: d
Clarification: All of the mentioned ways are applicable for crystallization.
11. Statement 1: Batch crystallizers are used if the throughput is high.
Statement 2: The operating cost of batch crystallizers is high.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: d
Clarification: Batch crystallizers are used if the throughput is low. The operating cost of batch crystallizers is high.
12. Statement 1: Batch crystallizers use the concept of cooling of hot solution/magma.
Statement 2: Control of particle size is poor in a batch crystallizer.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Batch crystallizers use the concept of cooling of hot solution/magma. Control of particle size is poor in a batch crystallizer.
13. Statement 1: Batch crystallizers are used for jaggery.
Statement 2: Particle size is controlled by stirring and scraping the concentrate from the vessel for better heat transfer.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Batch crystallizers are used for jaggery. Particle size is controlled by stirring and scraping the concentrate from the vessel for better heat transfer.
14. Scraped surface crystallizers can be used for viscous fluids up to 10000 cp.
a) True
b) False