Category: Food Processing Unit Operations Objective Questions

250+ TOP MCQs on Crystal Growth and Answers

Advanced Food Processing Unit Operations Questions and Answers on “Crystal Growth”.

1. What causes crystal growth?
a) Vapor
b) Solute
c) Melt
d) Vapor, solution and melt

Answer: d
Clarification: Crystals grow in one of three major ways; they are from a vapor, from a solution and from a melt where few molecules or ions come near each other in an appropriate orientation to form a stable submicroscopic aggregate.

2. Why is crystal growth important?
a) Increase the value of the product
b) Increase the size of the compound
c) Information about the structure of compounds
d) Information regarding the quality of product

Answer: c
Clarification: Crystals are very important and one of the reasons for the importance is that they give us information regarding the structure of compounds and also the function of the crystals and its effect on other compounds.

3. Which crystal grows the fastest?
a) Table salt
b) Epsom salt
c) Ferro sulphate salt
d) Sea salt

Answer: b
Clarification: The simplest and fastest crystals to grow are the Epsom salt (magnesium sulfate) crystals. These salts are used as healing agent and pain reliever.

4. Are crystals grown in cold temperature?
a) True
b) False

Answer: a
Clarification: Warm temperature helps in water evaporation which causes the crystals to grow more quickly. Crystals will still grow in cooler temperatures, but take longer time for the water to evaporate.

5. What is the purpose of seed crystal in crystal growth?
a) Nucleation center
b) Catalyst
c) Solvent
d) Solution

Answer: a
Clarification: The seed crystal acts as a nucleation center for the crystal and it promotes the growth of crystal. The orientation of seed crystal regulates the orientation of crystals.

6. Which of the following statements about frozen water are correct?
Statement 1:Water molecules slowed down and arrange themselves into fixed positions.
Statement 2: Water molecules freeze in a triangle pattern.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: a
Clarification: When water freezes, the water molecules slowed down arrange themselves into fixed positions. Water molecules freeze in hexagonal pattern and the molecules are further apart than they were in liquid water. The molecules in ice vibrate.

7. What happens when a crystal grows in size?
a) It becomes softer
b) It becomes smoother
c) It becomes rough
d) It becomes coarsely

Answer: b
Clarification: As a crystal grows, new atoms attribute easily to the rougher and less stable parts of the surface, but less easily to the flat and stable sides. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces.

8. At what temperature do ice crystals form?
a) Lower than 0°C
b) More than 0°C
c) At 0°C
d) At 4°C

Answer: a
Clarification: There are a number of ways in which ice crystals can form at temperature lower than 0°C. One method contains the rare presence of a particle known as an ice nucleus within a water droplet that acts as a catalyst for freezing.

9. How to prevent sugar from crystallizing?
a) By evaporating
b) By boiling
c) By adding an interferent
d) By adding an humectant

Answer: c
Clarification: The crystallization process is prevented by adding an interferent, like acid (vinegar, lemon and tartaric) and also corn syrup and glucose during the boiling procedure.

10. Is crystallization dependent on agitation?
a) True
b) False

Answer: a
Clarification: The agitation rate had a noticeable effect on size of the crystal. Higher the agitation rates, smaller is the crystal size. The lesser or no agitation leads to bigger size in crystals.

250+ TOP MCQs on Solid Liquid Equilibrium and Answers

Food Processing Unit Operations Multiple Choice Questions on “Solid Liquid Equilibrium”.

1. At what point does liquid and solid exist at equilibrium?
a) Double point
b) Triple point
c) Dew point
d) Freezing point
Answer: b
Clarification: The point at which the lines of liquid, solid and gas intersect represents the triple point. At the pressure and temperature of the triple point, all the phases exist in equilibrium.

2. Is the value of equilibrium constant independent of initial concentrations of the reactants and products?
a) True
b) False
Answer: a
Clarification: The value of equilibrium constant is independent of initial concentrations of the reactants and products. It is applicable only when concentrations of the reactants and products have attained their equilibrium state and is temperature dependent.

3. Who coined the term triple point?
a) James Thomson
b) Daniel Gabriel Fahrenheit
c) Carrier
d) Rudolf Clausius
Answer: a
Clarification: James Thomson coined the term triple point. Daniel Gabriel Fahrenheit invented thermometer. Carrier discovered that law of constant dew-point depression. Rudolf Clausius coined the term entropy.

4. Which of the following is not an example of freezing point depression?
a) Salt in water
b) Cooling the hot water
c) Alcohol in water
d) Mixing of impurities into a fine powder
Answer: c
Clarification: The freezing point depression is the decrease of the freezing point of a solvent on the addition of a non-volatile solute. Examples like alcohol in water, salt in water and the mixing of two solids such as impurities into a finely powdered drug.

5. What is peritectic?
a) A reaction between solid phase and gas phase to form a second solid phase
b) A reaction between solid phase and liquid phase to form a second solid phase
c) A reaction between gas phase and liquid phase to form a second solid phase
d) A reaction between solid phase and liquid phase to form a second liquid phase
Answer: b
Clarification: A reaction between solid phase and liquid phase to form a second solid phase is called peritectic reaction. These reactions are slow as the product phase form at the boundary between the two reacting phases thus it separates them and slows down the further reaction.

6. Are these statements about the dynamic equilibrium true?
Statement 1: Opposing processes occur at the same time.
Statement 2: Two processes occur at the same rate.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: When the system of ice and water is in dynamic equilibrium it can be concluded that both opposing processes occur at the same time and two processes occur at the same rate therefore the amount of ice and water remain constant.

7. What is the temperature at which the solid and liquid phases are at equilibrium?
a) Normal melting point
b) Bubble point
c) Dew point
d) Equilibrium point
Answer: a
Clarification: For any pure substance at atmospheric pressure, the temperature at which the solid and liquid phases are at equilibrium is called the normal freezing point or normal melting point of the component.

8. At equilibrium, the concentrations of N2=4.0 x10-3M, O2 = 5.2 x 10-3M and NO=3.9×10-3M in a sealed vessel at 800K. What will be Kc for the reaction?
a) 0.731
b) 0.073
c) 7.31
d) 0.0007
Answer: a
Clarification: For the reaction equilibrium constant, Kc can be written as,
Kc = [NO]2/[N2][O2]
= (3.9 x 10-3)2/(4.0×10-3M)(5.2×10-3M)
= 0.731

9. Is rate law and law of mass action are same?
a) True
b) False
Answer: b
Clarification: The difference between rate law and law of mass action is that, rate law considers only the reactants of a reaction whereas law of mass action considers both reactants and products of a reaction.

10. What is the other alternative name for equilibrium phase diagram?
a) p-v-T diagram
b) Bubble point diagram
c) Dew point diagram
d) Equilibrium point diagram
Answer: a
Clarification: The p-v-T diagram is also called as equilibrium phase diagram. The equilibrium conditions are explained with areas for solid, liquid, and vapor phases. It shows the areas where solid and liquid, solid and vapor, or liquid and vapor coexist in equilibrium.

250+ TOP MCQs on Drying – Moisture Content Determination Methods and Answers

Food Processing Unit Operations Multiple Choice Questions on “Drying – Moisture Content Determination Methods”.

1. _____________ is the amount of moisture a material will absorb relative to ambient temperature and humidity conditions.
a) Lyophilization
b) Hygroscopic action
c) Hydrophobic action
d) Hydrophilic action
Answer: b
Clarification: Hygroscopic action is the amount of moisture a material will absorb with respect to the temperature and humidity conditions. Due to hydroscopic action, the sample will continuously increase/ decrease in weight.

2. The measure of moisture content during thermogravimetric analysis is by the process of _________
a) water vaporization
b) freezing
c) oven drying
d) sun drying
Answer: a
Clarification: In thermogravimetric analysis, the moisture is determined by the loss of mass of a substance (normally moisture) when heated. This can be achieved by the water vaporization process. It is a complete, precise and approachable method to determine moisture.

3. Halogen and infrared drying are the examples of _________________
a) thermogravimetric analysis
b) freeze drying
c) non thermal analysis
d) pressure based analysis
Answer: a
Clarification: Halogen and infrared drying are the examples of thermogravimetric analysis. Halogen drying is up to twice as fast as traditional infrared technology. It is a complete, precise and approachable method to determine moisture.

4. The oven drying methodology consists of heating by ________
a) conduction
b) convection
c) radiation
d) both radiation and convection
Answer: b
Clarification: The most commonly used method for commercial purposes is oven drying methods for commercial purposes. The oven drying methodology consists of heating by convection. The demerits of this process are time and non-portability.

5. ______________ of moisture measurement is based on chemical reactions.
a) Lyophilization
b) Karl Fischer method
c) Halogen drying
d) Infrared drying
Answer: b
Clarification: Karl Fischer Method of moisture measurement is based on chemical reactions. A chemical reaction happens where the water is separated chemically from the rest of the sample. The water is then moved to other cell where it is measured. That measurement is equated with the initial mass of the sample and then moisture content is calculated.

6. _________ method id based on dielectric principle.
a) Electric moisture meter
b) Karl Fischer method
c) Lyophilization
d) Infrared drying
Answer: a
Clarification: Electric moisture meter method id based on dielectric principle. The electricity is measured by capacitance, conductance and radio frequency. They are inexpensive, easy to use and portable.

7. What is best method to use when the product have multiple layers that may have very different moisture levels?
a) Lyophilization
b) Karl Fischer method
c) Halogen drying
d) Microwave moisture meter
Answer: d
Clarification: Microwave moisture meter is best method to use when the product have multiple layers that may have very different moisture levels.In microwave method, the microwave is generally transmitted entirely through the samples.

8. Which one of the following is non-destructive moisture measurement?
a) Karl Fischer method
b) Nuclear moisture meter method
c) Loss on drying moisture method
d) Lyophilization
Answer: b
Clarification: In the Nuclear moisture meter technology, the energy is radiated into the sample and the amount of energy absorbed by the sample is measured. Beta radiation and gamma radiations are used for moisture determination. The relationship between absorbed energy and moisture content is then calculated to generate a calibration curve.

9. __________ uses reflectance & absorbance principles for calculating the moisture content.
a) Karl Fischer method
b) Nuclear moisture meter method
c) Loss on drying moisture meter method
d) Near infrared moisture meter method
Answer: d
Clarification: Near infrared moisture meter method uses absorbance and reflectance principles for determining the moisture content. This meter a beam of light on the product and then the light is filtered to a wavelength that excites the moisture molecules. The higher the amount of moisture content, higher is the amount of light absorbed.

10. The fundamental principle behind Karl Fischer method is based on the ____________
a) bunsen reaction on iodine in an aqueous medium
b) bunsen reaction between iodine and sulphuric acid in an aqueous medium
c) bunsen reaction between iodine and carbon dioxide in an aqueous medium
d) bunsen reaction between iodine and sulfur dioxide in an aqueous medium
Answer: d
Clarification: The fundamental principle behind Karl Fischer method is based on the bunsen reaction between iodine and sulfur dioxide in an aqueous medium where a primary alcohol like methanol is used as the solvent, and a base such as pyridine is used as the buffering agent.

250+ TOP MCQs on Fluid Statics & Fluid Dynamics and Answers

Food Processing Unit Operations Multiple Choice Questions on “Fluid Statics and Fluid Dynamics”

1. The force per unit area in a fluid is called as __________
a) differential pressure
b) fluid pressure
c) dynamic pressure
d) absolute pressure

Answer: b
Clarification: The force per unit area in a fluid is called as fluid pressure. Since the fluid does not have any shape, the forces can be exerted in all directions such as gravitational force, external force on the fluid.

2. Which principle explains the buoyant force of a fluid?
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: a
Clarification: Archimedes principle states that the object partially or fully submerged in a fluid will experience a buoyant force which is equal to the fluid weight in which object is displaced.

3. Hydraulic system works on the basis of ____________
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: b
Clarification: Hydraulic system works on the basis of Pascal’s principle. This principle states that when pressure is applied to a closed system of fluid, the pressure is transmitted to every part of the fluid and also to the walls of the container in which fluid is enclosed.

4. Are these statements about the Fluid mechanics true?
Statement 1: Fluid mechanics is a branch in chemistry that involves study of fluids.
Statement 2: Fluid mechanics can be divided into 2 major categories.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: c
Clarification: Fluid mechanics is a branch in physics that involves study of fluids such as liquids, plasma and gases. Fluid mechanics can be divided into 2 major categories. They are fluid statics (study based on fluids at rest) and fluid dynamics (study based on fluids in motion).

5. Which principle is used in designing the wings of airplanes?
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: c
Clarification: Bernoulli’s Principle is used in designing the wings of airplanes. According to the law of aerodynamics called Bernoulli’s principle, fast moving air has low pressure than slow moving air which has high pressure, so therefore pressure above wings is lower compared to pressure below the wings and this creates the lift in the plane that powers it to fly upwards.

6. Which of the following statements about applications of Pascal law in daily life are precise?

  • Statement 1: It is used in hydraulic pumps and hydraulic press.
  • Statement 2: It is not used in braking system in the vehicles.

a) True, False
b) True, True
c) False, True
d) False, False

Answer: a
Clarification: The applications of Pascal law in daily life is that it is used in hydraulic pumps and hydraulic press. It is also commonly used in in braking system in the vehicles where a fluid called brake fluid is used to transmit the pressure from the brake pedal to the all the vehicle wheels.

7. Who is the father of fluid mechanics?
a) Stephen Prokofievitch Timoshenko
b) Ludwig Prandtl
c) Singh Kapany
d) Samuel Colville Lind

Answer: b
Clarification: Ludwig Prandtl is called as the father of fluid mechanics. Stephen Prokofievitch Timoshenko is father of engineering mechanics. Singh Kapany is the father of fiber optics. Samuel Colville Lind is father of chemical kinetics.

8. What are applications of fluid statics?
a) Barometers, anemometer
b) Manometers, anemometer
c) Manometers, hygrometer
d) Manometer, barometers

Answer: d
Clarification: Manometer, barometers are used in measuring the pressure of the fluid based on the fluid state mechanism. Anemometer is used in measuring the wind speed and also the direction of the wind. Hygrometer is used to measure the humidity.

9. Fluid in static condition has shear stress.
a) True
b) False

Answer: b
Clarification: A fluid in static condition has no shear stress. The shear stress is known as force per unit area that is acting parallel to the inconsiderable surface element. It is mainly caused by the friction between fluid molecules due to viscosity of the fluid.

10. What causes the turbulence in fluid flow?
a) Kinetic energy
b) Pressure
c) Force
d) Potential energy

Answer: a
Clarification: During the flow of the fluid, the excessive kinetic energy that is present in the fluid causes the turbulence which overpowers the resistance of fluid. The turbulence is reduced by reducing Reynolds number.

250+ TOP MCQs on Size Reduction – Grinding Equipments and Answers

Food Processing Unit Operations Multiple Choice Questions on “ Size Reduction – Grinding Equipments”.

1. Identify this size reduction equipment?

a) Rolling compression mill
b) Burr mill
c) Jaw crusher
d) Hammer mill
Answer: c
Clarification: The working principle of the jaw crushers is motorized by a diesel or gas motor, the jaw crusher brakes materials in a crushing chamber. The materials are pushed inside the chamber from the top opening and when crushed they are released through the bottom opening.

2. What is other name for attrition mill?
a) Rolling compression mill
b) Burr mill
c) Jaw crusher
d) Hammer mill
Answer: b
Clarification: It is also known as burr mill. Grains are rubbed between the grooved flat faces of rotating circular disks where one plate is stationary and fixed with the body of the mill while the other one is rotating disk. Material is fed between the plates and is reduced by crushing and shear.

3. Which of the following forces acts in ball mill?
a) Gravitational force
b) Centrifugal force
c) Gravitational and centrifugal forces
d) Does not depend on any force
Answer: c
Clarification: In ball mills, product is released by the gravitational pull and drop to the bottom and the centrifugal force keeps the ball in contact with the mill wall. Due to centrifugal force, if the speed of rotation of mill is faster, the balls are carried to more distance therefore critical speed is required for rotational speed at which centrifuging occurs.

4. Which of the following statements about reduction ratio of crusherare correct?
Statement 1: It depends on the feed size of the equipment.
Statement 2: It is used in determining the mechanism of crusher.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: The Reduction Ratio is defined as the ratio of the feed size to the product size in any crushing operation. It is very useful in determining mechanism of crusher and type of size reduction.

5. What is the working principle of ball mill?
a) Impact and attrition
b) Compression and attrition
c) Shear and compression
d) Tear and impact
Answer: a
Clarification: Ball mill works on the principle of impact and attrition. Size reduction is done by impact as the balls drop from near the top of the shell. A ball mill consists of a hollow cylindrical shell rotating about its axis.

6. What is the working principle of triple roller mill?
a) Impact
b) Compression
c) Shear
d) Tear
Answer: c
Clarification: A triple roll mill is a machine that uses shear force which is created by three horizontally positioned rolls rotating in the opposite directions and also with different speeds relative to each other. This is done in order to refine, mix, disperse and homogenize viscous materials.

7. Which of the following machine is not used for fine grinding?
a) Jaw crushers
b) Ball mill
c) Hammer mill
d) Attrition mill
Answer: a
Clarification: Ball mill, Hammer mill and attrition mill are used for fine grinding whereas the jaw crushers, crusher rolls and gyratory crushers are used for coarse grinding.

8. What is the working principle of hammer mill?
a) Impact
b) Compression
c) Shear
d) Tear
Answer: a
Clarification: A hammer mill is a mill which is used to shred or crush larger material into smaller pieces by the repeated blows of little hammers. It creates impact force.

9. Which of the following forces acts in attrition mill?
a) Impact and crush
b) Compression and impact
c) Shear and crush
d) Tear and impact
Answer: c
Clarification: It is also known as burr mill. Grains are rubbed between the grooved flat faces of rotating circular disks where one plate is stationary and fixed with the body of the mill while the other one is rotating disk. Material is fed between the plates and is reduced by crushing and shear.

10. Are gyratory crusher and cone crusher same?
a) True
b) False
Answer: b
Clarification: Gyratory crushers are for primary crushing. Cone crushers are used for secondary or tertiary crushing for making a cubical product for feeding to process equipment.

250+ TOP MCQs on Crystallization – Nucleation Mechanism and Answers

Food Processing Unit Operations Multiple Choice Questions on “ Crystallization – Nucleation Mechanism”.

1. What is nucleation in crystallization?
a) It is the initial step in crystallization
b) It is the final step in crystallization
c) It is the step where nucleus is added
d) It is the sub category crystallization
Answer: a
Clarification: Nucleation is the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapor, in which a small number of molecules arranged in a pattern.

2. How to initiate crystallization?
a) Adding seed crystals
b) Adjusting temperature
c) Adjusting pressure
d) Adjusting concentration
Answer: a
Clarification: Crystallization can be spontaneous or can be done by addition of small amount of the seed crystal or the pure compound to the saturated solution.

3. How does temperature affect nucleation?
a) Nucleation is directly proportional to temperature
b) Nucleation is indirectly proportional to temperature
c) Nucleation and temperature are always at equilibrium
d) Nucleation and temperature does not depend on each other
Answer: b
Clarification: The decrease in nucleation centers at high temperature interprets that decrease in supersaturation, would increase in critical size of nucleus and free energy of nucleus formation.

4. What is nucleation in freezing?
a) Process of gathering of molecules into tiny clusters
b) It is the final step in freezing
c) It is the step where nucleus is added
d) It is the sub category freezing
Answer: a
Clarification: Nucleation is a process where the molecules or the atoms in a liquid start to gather into tiny clusters, arranging to form the crystal structure of the solid.

5. Which of the following statements about primary nucleation are correct?
Statement 1:The appearance of the first crystal is called primary nucleation time.
Statement 2:It describes the transition to a new phase.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: The time until the presence of the first crystal is called primary nucleation time, it refers to the first nucleus to form. It describes the transition to a new phase which does not rely on the new phase which is already present.

6. What is homogeneous nucleation?
a) Spontaneously generated nuclei
b) Randomly generated nuclei
c) Orderly generated nuclei
d) Randomly and spontaneously generated nuclei
Answer: d
Clarification: Homogeneous nucleation is the process by which nuclei that are randomly and spontaneously generated grow irreversibly to form a new phase.

7. What is seeding in crystallization?
a) It is the initial step in crystallization
b) It is the final step in crystallization
c) It is the step where nucleus is added
d) It is the sub category crystallization
Answer: c
Clarification: Crystal seeding is the process of adding homogeneous or heterogeneous crystals to a crystallizing solution to nucleate and grow more crystals.

8. What are the factors that affect crystallization seedling?
a) Temperature and pressure
b) Polymorphism of the crystals and pressure
c) Crystal size distribution and temperature
d) Crystal size distribution and polymorphism of the crystals
Answer: d
Clarification: Crystal seeding is the technique to add homogeneous or heterogeneous crystals to a crystallizing solution for nucleating and growing of more crystals. This is done by controlling the polymorphism of the crystals that are formed and crystal size distribution.

9. Which of the following statements about secondary crystallization are correct?
Statement 1:Secondary nucleation is the formation of nuclei from pre-existing crystals.
Statement 2: Only secondary nucleation increases the number of crystals in the system.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: Secondary nuclei are crystal nuclei that are produced from a pre-existing crystal. Primary and secondary nucleation increases the number of crystals in the system and depends on crystals which are already present.

10. Is supersaturation the driving force for all solution crystallization processes?
a) True
b) False
Answer: a
Clarification: Supersaturation is the driving force for all solution crystallization processes where the supersaturated solution spontaneously separate into pure crystals of the solute and a less concentrated solution.