This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Principles of Crystallization”.
1. What is meant by crystallization?
a) Concentration of atoms into a highly structured form
b) Solidification of atoms into a highly structured form
c) Solidification of solution
d) Concentration of solution
View Answer
Explanation: Crystallization is solidification of atoms into a highly structured form called a crystal. It is the solid-liquid separation and purification technique where mass transfer occurs from the liquid solution to a pure solid crystalline phase.
2. When is supersaturation attained?
a) When the solvent contains more solute
b) When the solute contains more solvent
c) When the solvent contains less solute
d) When the solute contains less solvent
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Explanation: Supersaturation is defined as the state in which the solvent contains more dissolved solids (solute) than can usually be accommodated at that temperature.
3. Which of the following is crystallization?
a) Solid-solid separation
b) Solid-liquid separation
c) solid-gas separation
d) Liquid- gas separation
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Explanation: Crystallization is solidification of atoms into a highly structured form called a crystal. It is the solid-liquid separation and purification technique where mass transfer occurs from the liquid solution to a pure solid crystalline phase.
4. What is purpose of recrystallization?
a) To purify chemicals
b) To dissolve crystals
c) Continuous process of crystallization
d) To clean crystallizers
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Explanation: Recrystallization is a technique used to purify chemicals. By dissolving both impurities and a compound in an appropriate solvent, either the desired component or impurities can be removed from the solution, parting the other behind.
5. How does concentration affect crystallization?
a) Increase in concentration leads to large crystals
b) Decrease in concentration leads to large crystals
c) Increase in concentration leads to small crystals
d) Decrease in concentration leads to small crystals
View Answer
Explanation: When the water evaporates faster the concentration increases. The larger crystals can accommodate larger the surface where more molecules can be added.
6. What are crystallization techniques?
a) Gradual cooling and diffusion
b) Diffusion and sharp cooling
c) Gradual cooling and sharp cooling
d) Sharp cooling and crystallization
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Explanation: Crystallization is a technique used to for solids purification. The two common methods of crystallization are gradual cooling and diffusion.
7. Why is a supersaturated solution unstable?
a) Concentration is higher than equilibrium concentration
b) Concentration is lower than equilibrium concentration
c) Concentration is equal to equilibrium concentration
d) Contains impurities
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Explanation: The solute in a supersaturated solution is present in concentration higher than equilibrium concentration; therefore the supersaturated solutions are unstable.
8. What are factors affecting crystallization?
a) Degree of agglomeration
b) Crystal shape
c) Particle size distribution
d) Particle size distribution, crystal shape, degree of agglomeration
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Explanation: The factors affecting crystallization are particle size distribution, crystal shape, degree of agglomeration, purity and caking behavior.
9. How does temperature affect nucleation?
a) When temperature increases the nucleation decreases
b) When temperature increases the nucleation increases
c) Nucleation is not dependent on Temperature
d) When temperature increases the nucleation increases and then decreases
View Answer
Explanation: When the nucleation decrease drastically as the temperature increases. Thus, the decrease in nucleation at higher temperature leads to the decrease in supersaturation.
10. Is crystallization a chemical change?
a) True
b) False
View Answer
Explanation: In crystallization, there is no chemical change occurs in the chemical compound as there is no new products are created. Therefore, crystallization is a physical change.
Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.
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