Category: Food Processing Unit Operations Objective Questions

250+ TOP MCQs on Crystallizers and Answers

Food Processing Unit Operations Multiple Choice Questions on “Crystallizers”.

1. What is the main feature of circulating liquid crystallizer?
a) Efficiency is high
b) Supersaturation is created in a separate region
c) Low capital cost
d) Easy maintenance
Answer: b
Clarification: The specialty of circulating liquor crystallizer is that supersaturation is produced in a separate region before the liquor flows into crystal suspension vessel.

2. What is evaporative crystallization?
a) Evaporation of the solvent
b) Separate components at higher temperature
c) Separate components at lower temperature
d) Mix components at higher temperature
Answer: a
Clarification: Crystallization is due to evaporation of the solvent. It creates a vapor and a suspension of crystals in the mother liquor. The evaporation heat is added in the vapor stream.

3. Which of the manufacturing unit use melt crystallizers?
a) Ice creams
b) Automobiles
c) Salt preparation
d) Semiconductor
Answer: d
Clarification: Crystals form in these crystallizers is from the high-quality melts which has large yields, pure and defect free crystals. These are typically used for semiconductor manufacture.

4. How are crystals in precipitation vessels?
a) Small size
b) Large size
c) Medium size
d) Very large size
Answer: a
Clarification: In precipitation vessels, the feed streams entering the vessel produce high supersaturation levels by chemical reaction and therefore produces very rapidly a large numbers of small crystals.

5. Which of the following statements about crystallizers design are correct?
Statement 1:Selection of supersaturation generation method is not necessary.
Statement 2:Choice of batch or continuous operation is important.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: A crystallizer’s design sequence involves the basic data collection following selection of the supersaturation generation method and choosing the batch/continuous operation.

6. What is salting out process?
a) Addition of salt to precipitate the product from solvent
b) Addition of salt to precipitate the product from solution
c) Removal of salt to in the product
d) Removal of salt to precipitate the product from solution
Answer: b
Clarification: Salting out is the process where salt with common ion is added to precipitate product from solution. This is similar to the characteristics of reaction crystallization.

7. How is product purity increased?
a) Boiling
b) Sweating
c) Freezing
d) Adding solute
Answer: b
Clarification: The purity of is increased by sweating process. In this process, the impurities are removed out of the solidified crystals before recovery process. The period of released pressure from the substance is used as sweating time

8. What are the key parameters of rate of generation of supersaturation?
a) Cooling and addition rate
b) Evaporation and addition rate
c) Cooling and evaporation
d) Cooling, evaporation or addition rate
Answer: a
Clarification: This is a low temperature distillation method which allows for separation of nonvolatile, water immiscible substances at temperatures below boiling point of individual constituents. This preserves components that will be disrupted at high temperatures.

9. Which of the following statements about continuous crystallizers are correct?
Statement 1:These produce a consistent product.
Statement 2: More energy efficient.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Continuous crystallizers produce a consistent product and more energy efficient than batch process. Therefore the continuous crystallizers are used in high-production rate systems. More process knowledge is required.

10. Is feed rate the only adjustable parameter in continuous crystallizers?
a) True
b) False
Answer: b
Clarification: The only adjustable parameters in the continuous crystallizers are usually the feed rate, residence time and supersaturation generation rate.

250+ TOP MCQs on Equilibrium Concentration Relationship and Answers

Food Processing Unit Operations Problems on “Equilibrium Concentration Relationship”.

1. What is equilibrium constant expression?
a) The ratio of the concentrations of the reactants and molar constant and products
b) The ratio of the concentrations of the products and reactants
c) The ratio of the concentrations of the reactants and products
d) The ratio of the concentrations of the catalyst and products
Answer: c
Clarification: The ratio of the concentrations of the reactants and products is called as equilibrium constant expression. When the reaction reaches equilibrium, the association between the concentrations of the reactants and products termed by the equilibrium constant expression is always same.

2. How does increase in concentration affect equilibrium?
a) It will shift towards the products.
b) It will shift towards the reactants.
c) No change
d) It will shift according to pressure change
Answer: a
Clarification: When there is increase in concentration the equilibrium will shift towards the products. There will be increase in product formation and there will be decrease in concentration of the reactants as the concentration of the products increases.

3. What affects equilibrium?
a) Changes in concentration
b) Changes in and pressure
c) Changes in temperature
d) Changes in concentration, temperature, and pressure
Answer: d
Clarification: Changes in concentration, temperature, and pressure can affect the position of equilibrium of a reversible reaction. If the forward reaction is endothermic, then there is an increase in temperature that causes the system to shift toward the products.

4. Do catalysts affect equilibrium?
a) True
b) False
Answer: b
Clarification: The catalyst speeds up the forward and back reaction to the same extent and addition of a catalyst does not affect the relative rates of the two reactions and cannot affect the position of equilibrium.

5. What is the relation between Kp and K?
a) Kp=K(RT)Δn
b) Kp=K-(RT)Δn
c) Kp=K+(RT)Δn
d) Kp=K/(RT)Δn
Answer: a
Clarification: The relation between Kp and K is Kp=K(RT)Δn. An equilibrated system that contains products and reactants in a single phase is a homogeneous equilibrium where as a system whose reactants, products are in more than one phase, it is called as heterogeneous equilibrium.

6. The equilibrium constant for the reaction of nitrogen and hydrogen to give ammonia is 0.95 at 745 K. The balanced equilibrium equation is as follows:
N2(g)+3H2(g)⇌2NH3(g)
What is Kp for this reaction at the same temperature?
a) 2.54×10-4
b) 3.85×10-4
c) 4.27×10-4
d) 3.73×10-4
Answer: a
Clarification: This reaction has 2 moles of gaseous product and 4 moles of gaseous reactants, so Δn=(2−4)=−2. We know K, and T=745K.
Kp=K(RT)−2
0.95 x {[0.08206(L⋅atm)/(mol⋅K)][745K]}-2 = 2.54×10-4.

7. What is use of law of mass action in equilibrium?
a) Predicts behaviors of solutions in dynamic equilibrium
b) To calculate the concentration of products
c) To calculate the concentration of reactants
d) Predicts behaviors of solutes
Answer: a
Clarification: Law of mass action in equilibrium predicts behaviors of solutions in dynamic equilibrium. The law of mass action defines that the rate of the chemical reaction is directly proportional to the product of the activities or the reactants concentration.

8. Who discovered law of mass action?
a) Guldberg and Waage
b) Newton
c) Henricus
d) Gyarmati
Answer: a
Clarification: Guldberg and Waage recognized that chemical equilibrium is a dynamic process where rates of forward reactions and rate of backward reactions must be equal at chemical equilibrium.

9. Are these statements about the Equilibria involving physical processes true?
Statement 1: Equilibrium is possible only in an open system.
Statement 2: All measurable properties of the system remain constant.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Equilibrium is possible only in a closed system. All measurable properties remain constant of the system. Both the opposing processes occur at the same rate. It is a dynamic state but stable condition.

10. Is equilibrium mean equal concentrations?
a) True
b) False
Answer: b
Clarification: Equilibrium does not essentially mean that substances present are in equivalent amounts. It is defined that the reaction has reached to a point where the reactant’s concentrations and product’s concentration are static with time and the forward and backward reactions have the equal rate.

Food Processing Unit Operations Problems,

250+ TOP MCQs on Drying – Psychrometry and Answers

Food Processing Unit Operations Multiple Choice Questions on “Drying – Psychrometry”.

1. What is psychometric chart?
a) It is the graphical representation of thermodynamic properties
b) It is the graphical representation of chemical properties
c) It is the graphical representation of drying properties
d) It is the graphical representation of mechanical properties
Answer: a
Clarification: Psychometric chart is a graphical representation of thermodynamic properties of moist air at one atmosphere like wet bulb temperature, dry bulb temperature, dew point temperature, humidity ratio, relative humidity, specific volume and enthalpy.

2. Who invented the psychometric chart?
a) Dr Richard Seligman
b) George Babcock
c) George Brayton
d) Willis H. Carrier
Answer: d
Clarification: Dr Richard Seligman invented heat exchanger. George Babcock invented boiler. George Brayton invented engine. Willis H. Carrier invented psychometric chart.

3. Which lines indicate wet bulb temperatures in the psychometric charts?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves
Answer: a
Clarification: The temperature read by the thermometer where the bulb of thermometer is enclosedwith a wet cloth is called as wet bulb temperature. If the reading of the wet bulb temperature is lower, this indicates that the surroundings have lower humidity.When the relative humidity is 100%, then wet bulb temperature is equal to the air temperature.

4. Which lines indicate dry bulb temperatures in the psychometric chart?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves
Answer: b
Clarification:The dry-bulb temperature is defined as the temperature of air which is measured by a thermometer that is freely exposed to the air, but protected from radiation and the moisture content. It is the true thermodynamic temperature.Dry bulb temperatures in the psychometric charts areindicated by vertical lines.

5. Which lines indicate relative humidity in the psychometric charts?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves
Answer: d
Clarification: The relative humidity is defined as the amount of water vapor present in air.It is normally expressed as a percentage of the amount needed for saturation at the same temperature. Relative humidity in the psychometric charts is indicated by curves.

6. What is another name for humidity ratio?
a) Mixing ratio
b) Water ratio
c) Relative humidity ratio
d) Bound water ratio
Answer: a
Clarification: Humidity ratio is the fraction of mass of water vapor per unit mass of dry air at the given conditions thermodynamic conditions. It is known as the moisture content or the mixing ratio. It is typically plotted as the ordinate on the vertical axis of the graph.

7. Who invented the sling psychrometrer?
a) Sir John Leslie
b) Leonardo da Vinci
c) George Babcock
d) George Brayton
Answer: a
Clarification: Sir John Leslie invented the sling psychrometrer. A sling psychrometer is an instrument that measures the dew point and relative humidity in an area. It has two thermometers, they are a wet bulb and a dry bulb.

8. What is wet bulb depression?
a) Difference between dry bulb temperature and wet bulb temperature at any point
b) Difference between relative humidity and wet bulb temperature at any point
c) Difference between dew point and wet bulb temperature at any point
d) Difference between dry bulb temperature and dew point temperature at any point
Answer: a
Clarification: The wet bulb depression is defined as the difference between dry bulb temperature and wet bulb temperature at any point. It indicates relative humidity of the air.

9. What is dew point depression?
a) Difference between dry bulb temperature and dew point temperature of air
b) Difference between wet bulb temperature and dew point temperature of air
c) Difference between relative humidity and dew point temperature of air
d) Difference between wet bulb depression and dew point temperature of air
Answer: a
Clarification: The dew point depression is defined as the difference between dry bulb temperature and dew point temperature of air. As the dew point depression deals with the moisture in the atmosphere, it is very important in forest, agricultural and particularly in forecasting wildfires.

10. Is dew point same as wet bulb?
a) True
b) False
Answer: b
Clarification: The wet bulb temperature is defined as the temperature that a wet bulb which is covered by wet cotton wick will reach from evaporative cooling. Whereas the dew point temperature is the temperature that the atmosphere would have to be cooled for complete saturation of air with water.

250+ TOP MCQs on Pressure Measurement in a Fluid and Answers

Food Processing Unit Operations Questions and Answers for Freshers on “Pressure Measurement in a Fluid”.

1. Manometer is used for measuring __________
a) pressure
b) speed
c) Fathometer
d) density

Answer: a
Clarification: Manometer is used for measuring pressure. Tachometer is used for measuring speed. Hydrometeris used for measuring density. Fathometeris used for measuring ocean depth.

2. Which instrument is used to measure medium pressure?
a) Bourdon tube pressure gauges
b) Barometric sensor
c) Piezoelectric pressure sensor
d) Piezoresistive pressure sensor

Answer: a
Clarification: Bourdon tube pressure gauges are widely used to measure medium to high pressure. The range of pressure it can detect is from 600mbar to 4000 bar. The measuring unit consists of curved tube with circular, spiral or coiled shape called as bourdon tube.

3. Which pressure instrument is used inweather networks?
a) Bourdon tube pressure gauges
b) Barometric sensor
c) Piezoelectric pressure sensor
d) Piezoresistive pressure sensor

Answer: b
Clarification: Barometric sensoris used in weather networks. These sensors measure the fluctuations in the pressure exerted by atmosphere. They are enclosed with a data logger and is well protected from precipitation, water ingress and condensing humidity.

4. _____________ measure dynamic pressure.
a) Bourdon tube pressure gauges
b) Barometric sensor
c) Piezoelectric pressure sensor
d) Piezoresistive pressure sensor

Answer: c
Clarification: Piezoelectric pressure sensors measure dynamic pressure. The dynamic pressure measurements include the blast, ballistics, turbulence and engine combustion. These sensors have the ability to measure quasi static pressures. They are fast response, extended ranges, ruggedness and high stiffness

5. Which instrument uses the change in electric resistance to measure the pressure?
a) Bourdon tube pressure gauges
b) Barometric sensor
c) Piezoelectric pressure sensor
d) Piezoresistive pressure sensor

Answer: d
Clarification: Piezoresistive pressure sensoruses the change in electric resistance of a material when stretched to measure the pressure. Due to the simple design and robustness, this instrument is used for wide range of applications. These are used for gauge, absolute and relative pressure measurement in both high and low pressure applications.

6. Which of the following statements about pressure transmitters are correct?
Statement 1: It contains pressure sensor and signal conditioner.
Statement 2:There are four main types of pressure transmitters.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: b
Clarification: Pressure transmitters contain pressure sensor and a signal conditioner to amplify the weak electrical signals that are sent through the pressure sensors for measuring the pressure. There are four main types of pressure transmitters. They are absolute, gauge, differential pressure, and multivariable.

7. Which of the following statements about vacuum gauges are correct?
Statement 1: Thermal vacuum gauges sense the cooling effect of a heated filament.
Statement 2: Thermal vacuum gauges designed to measure high pressures.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: a
Clarification: The vacuum gauges designed to measure very low pressures or in a vacuum.The vacuum gauges sense the cooling effect of a heated filament on the gases in the vacuum chamber being measured. It consists of heated thin wire. These resemble as thermal flow meters, where heated wire is placed into the flow steam and infer the flow by measuring the speed with which heat is dissipated. The vacuum gauges sense the cooling effect of a heated filament on the gases in the vacuum chamber being measured.

8. One pascal is equivalent to _______ of force applied over an area of one meter squared.
a) one newton
b) 100 newton
c) 1000 newton
d) 10 newton

Answer: a
Clarification: One pascal is equivalent to one newton of force applied over an area of one meter squared. The pascal is the unit of pressure and it is named after the scientist Blaise Pascal.

9. The manomeric fluid density should be ______than that of flowing fluid.
a) greater
b) smaller
c) equal
d) very small

Answer: a
Clarification: The manometer is also called as wet meter. The density of the manomeric fluid should be greater than that of flowing fluid. Mercury can be used because it has a high density and therefore manometer size is minimized.

10. What is relation between PSI and Bar?
a) 1 Bar = 14.5 Psi
b) 1 Bar = 20 Psi
c) 1 Bar = 201 Psi
d) 1 Bar = 1 Psi

Answer: a
Clarification: For all pressure unit conversions, Psi (pounds per square inch) is 1 pound of force per square inch. Bar is equal to the atmospheric pressure at sea level.

250+ TOP MCQs on Size Reduction – Oil Extraction and Answers

Food Processing Unit Operations Multiple Choice Questions on “Size Reduction – Oil Extraction”.

1. Why hexane is used for extraction?
a) Easy oil recovery
b) Higher boiling point
c) Easy separation
d) Catalyst
Answer: a
Clarification: Hexane is commonly used for oil extraction because of the easy oil recovery, narrow boiling point and also has exceptional solubilizing capability.

2. What is solvent extraction process?
a) Separate components based boiling point
b) Separate compounds based on their relative solubility
c) Separate components at lower temperature
d) Separated through evaporation
Answer: b
Clarification: Solvent extraction is oil separation technique which is used to separate compounds based on their relative solubility in two dissimilar immiscible liquids, usually water and an organic solvent.

3. Which of the following method uses odorless fats as solvent?
a) CO2 Extraction
b) Maceration
c) Enfleurage
d) Cold Press Extraction
Answer: c
Clarification: In the enfleurage extraction method, petals are placed between layers of purified animal fat, where it gets saturated with flower oil, and alcohol. It is used to recover citrus oils from fruit peels.

4. What is maceration extraction?
a) Immersing a plant in a liquid
b) Separate compounds based on their relative solubility
c) Separate components at lower temperature
d) Separated through evaporation
Answer: a
Clarification: A maceration extraction consists of preserving contact between the plant and liquid for a period of time. It is an extractive technique that is conducted at room temperature where plant is immersed in a liquid like water, oil, alcohol.

5. Which of the following statements about cold pressingare correct?
Statement 1: Produces higher yield.
Statement 2: Produces lower quality of oil.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: d
Clarification: Cold presses are typically mechanically operated. Cold pressing usually produces a lower yield, but higher quality of oil.

6. What is the other name for expression method?
a) CO2 Extraction
b) Maceration
c) Enfleurage
d) Cold Press Extraction
Answer: d
Clarification: Expression is method is also called as cold pressed method of extraction where there is no heat needed for extracting essential oil. In this process, the oil is forced from the material under high mechanical pressure.

7. What solvents are used to extract essential oils?
a) Petroleum ether
b) Ammonia
c) Water
d) Distilled water
Answer: a
Clarification: Essential oils are extracted by using solvents like ethanol, petroleum ether, hexane, and methanol. They have easy oil recovery, narrow boiling point and also have exceptional solubilizing capability.

8. How to increase the extraction efficiency?
a) Crush the material
b) Dissolve in water
c) Dissolve in distilled water
d) Dry the material
Answer: a
Clarification: To increase the extraction efficiency the material should be crushed so that the components are easily dissolved into the solvent. This also results in low time consumption.

9. Is cold extraction the same as cold pressed??
a) True
b) False
Answer: b
Clarification: Cold pressed and cold extraction refers to oils that aren’t heated over 27°C during processing, therefore retains nutrients. Cold pressed oil is made by pressing product in the traditional way whereas cold extraction is oil obtained using centrifuge.

10. How do you remove hexane from oil?
a) Vacuum distillation
b) CO2 Extraction
c) Maceration
d) Enfleurage
Answer: a
Clarification: To remove the hexane from oil, the miscella is treated in a vacuum distillation process. The hexane is evaporated during the distillation method which is condensed and separated from water in a decanter. The recovered hexane is then reused in the extractor.

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.