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Multiple choice question for engineering

Set 1

1. Statement 1: Drying is used for preservation of food.
Statement 2: Convective drying is indirect drying and conductive drying is direct drying.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: a [Reason:] Drying is used for preservation of food as the removal of moisture helps it stay longer. Conductive drying is indirect drying and Convective drying is direct drying.

2. On wet basis, the denominator stays constant whereas in moisture content on dry basis, the denominator changes.
a) True
b) False

View Answer

Answer: b [Reason:] Wet basis involves the amount of moisture content also in the denominator which at different times will be different. Whereas, in dry basis analysis, the denominator is only the weight of the solid. Hence it does not change. Therefore, the correct sentence is – On dry basis, the denominator stays constant whereas in moisture content on wet basis, the denominator changes.

3. Moisture on dry basis cannot be more than hundred percentage.
a) True
b) False

View Answer

Answer: b [Reason:] In dry basis analysis, the denominator is only the weight of the solid. Hence it can be lesser than the overall moisture content which is the numerator. ((Weight of moisture present at any time)/(Weight of dry solid))

4. food-engineering-questions-answers-unit-operations-dehydration-1-q4
The x- axis is the moisture content on dry basis. The y-axis is the equilibrium moisture content.
Which of the following shows Bound moisture content?
a) AIEG
b) GIBF
c) GFHC
d) EGHD

View Answer

Answer: a [Reason:] AIEG represents the bound moisture content.

5. The EMC-RH data is fitted to the Henderson’s equation. Which of the following is true about the relative humidity with respect to food technology terminology?
a) It is also called water activity
b) It is irrelevant with respect to food technology
c) None of the mentioned
d) All of the mentioned

View Answer

Answer: a [Reason:] Relative humidity is also called water activity in food technology.

6. Drying rate curve is plot between _____ and _____
a) Critical moisture content, critical humidity
b) Critical moisture content, drying rate
c) Critical humidity, drying rate
d) Moisture content, drying rate

View Answer

Answer: d [Reason:] Drying rate curve is plot between Moisture content and drying rate.

7. The point where the constant drying period changes to falling rate period is called _____
a) Equilibrium moisture content
b) Critical moisture content
c) Critical humidity
d) Bound moisture content

View Answer

Answer: b [Reason:] The point where the constant drying period changes to falling rate period is called Critical moisture content.

8. Which of the following denotes gas phase mass transfer coefficient?
a) Sherwood number
b) Lewis number
c) Schmidt number
d) None of the mentioned

View Answer

Answer: b [Reason:] Lewis number denotes gas phase mass transfer coefficient as the measurement of gas phase mass transfer is not that easy and needs to be depicted by a dimensionless quantity.

9. Statement 1: Removing of moisture content for grains in the food industry follows the thin layer model of drying bed.
Statement 2: The model for removing moisture from grains is computerized to find out the exact amount of time of exposure of grains for removal of moisture.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Removing of moisture content for grains in the food industry follows the thin layer model of drying bed. The model for removing moisture from grains is computerized to find out the exact amount of time of exposure of grains for removal of moisture.

10. What does the thin layer model of drying beds in drying of grains depend on?
a) Temperature of air
b) Air flow
c) Initial moisture content
d) All of the mentioned

View Answer

Answer: d [Reason:] Thin layer model of drying beds in drying of grains depends on all of the mentioned points.

11. Cabinet tray dryers are not very effective as they do not completely strip off the moisture content from the food item. Hence, they need to be combined with another dryer for effective results.
a) True
b) False

View Answer

Answer: a [Reason:] Cabinet tray dryers are not very effective as they do not completely strip off the moisture content from the food item. Hence, they need to be combined with another dryer for effective results.

12. Statement 1: Cabinet tray dryers are used for storing grains.
Statement 2: Cabinet tray dryers are used for low cost foods.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: d [Reason:] Bin dryers are used for storing grains. Cabinet tray dryers are not very effective as they do not completely strip off the moisture content from the food item. Hence, they’re used for low cost foods.

13. Tunnel dryer is only a continuous version of a cabinet tray dryer.
a) True
b) False

View Answer

Answer: a [Reason:] Tray dryers are operated under batch conditions. Tunnel dryers just move these trays while hot air is simultaneously supplied.

Set 2

1. Shifting of a pair of ripened apples from the store house to the vegetable cart is called mass transfer.
a) True
b) False

View Answer

Answer: b [Reason:] Shifting of a pair of ripened apples from the store house to the vegetable cart is only called material handling.

2. Statement 1: When alcohol is allowed to move from chamber A to chamber B when a barrier between them is removed, it is called multi phase diffusion.
Statement 2: When oxygen is made to diffuse into water, it’s called continuous molecular diffusion.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: d [Reason:] Alcohol and water are miscible in each other. They aren’t different phases. Hence, it cannot be called multi phase diffusion. When oxygen is made to diffuse into water, it’s called continuous molecular diffusion.

3. Velocity gradient is the main driving force in mass transfer.
a) True
b) False

View Answer

Answer: b [Reason:] Velocity gradient is the main driving force in momentum transfer.

4. Statement 1: A phase boundary exists between alcohol and oxygen.
Statement 2: Phase boundary varies with agitation. It is inversely proportional to the amount of agitation provided.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Both the statements pertaining to phase boundary are true.

5. A phase boundary between alcohol and water exists.
a) True
b) False

View Answer

Answer: b [Reason:] Alcohol and water are miscible in each other. They aren’t different phases. Hence, no phase boundary exists.

6. Statement 1: Diffusion is faster than convective mass transfer.
Statement 2: Mass transfer is proportional to the area of contact.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: d [Reason:] Convective mass transfer is faster than diffusion. Mass transfer is proportional to the area of contact.

7. Statement 1: Resistance is inversely proportional to the inter-facial area.
Statement 2: The inter-facial area of a body is the area of the dispersed phase in a unit volume of the vessel.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Resistance is inversely proportional to the inter-facial area. The inter-facial area of a body is the area of the dispersed phase in a unit volume of the vessel.

8. Ratio of equilibrium concentrations of solute A in liquid phase and gas phase i.e. CAL* and CAg* respectively is α. α is called _____
a) Diffusion coefficient
b) Distribution coefficient
c) Mass transfer coefficient
d) None of the mentioned

View Answer

Answer: b [Reason:] CAL*/CAg* = α = Distribution coefficient.

9. Statement 1: Diffusion of gas component through the resistive film to the bulk of the liquid is the rate determining step.
Statement 2: Diffusion of gas component through the gas-liquid inter-phase is the rate determining step.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: a [Reason:] Diffusion of gas component through the resistive film to the bulk of the liquid is the rate determining step as the resistance during this is maximum.

10. In a packaging of dry grapes, the packaging material is made of polyethylene. The dry grapes have certain moisture content. Which of the following is true with respect to the diffusion of certain amount of moisture through the packing?
a) The moisture will not diffuse
b) The diffusion in this case is called permeability
c) None of the mentioned
d) Both of the mentioned

View Answer

Answer: b [Reason:] In packaging (especially polymers) terminology, the term diffusion is referred to as permeability.

Set 3

1. Statement 1: Distillation is not used very widely in the food industry.
Statement 2: Steam distillation can be done when the volatile component is not miscible in water.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Distillation is not used very widely in the food industry. Steam distillation can be done when the volatile component is not miscible in water.

2. Out of the limited applications of distillation in the food industry, which of the following is an application?
a) Use in brewer industry
b) Use in solvent recovery industry
c) Use in steam distillation
d) All of the mentioned

View Answer

Answer: d [Reason:] All of the mentioned industries is where distillation is used.

3. This method is used in food processing for removal of bad odours from food.
a) Flash distillation
b) Steam distillation
c) Batch distillation
d) Gas adsorption

View Answer

Answer: b [Reason:] Steam distillation is used in food processing for removal of bad odours from food.

4. When the mass balance in a distillation column is F = B + D, how can D that is the distillate be increased?
a) Decreasing vacuum in distillation unit
b) Increase vacuum in distillation unit
c) None of the mentioned
d) Both of the mentioned

View Answer

Answer: b [Reason:] By increasing the vacuum in the distillation unit, the vapor-liquid separation takes place.

5. Statement 1: Rectification involves the liquid and vapors to pass a cascade of stages.
Statement 2: In rectification, both heat and mass transfer takes place till equilibrium is reached.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Rectification involves the liquid and vapors to pass a cascade of stages. In rectification, both heat and mass transfer takes place.

6. When there is a mixture of liquids present, the boiling point lies between the boiling points of both the components.
a) True
b) False

View Answer

Answer: a [Reason:] When there is a mixture of liquids present, the boiling point lies between the boiling points of both the components.

7. Statement 1: Vapor phase is always more of volatile components.
Statement 2: Liquid phase is always more of high boiling point liquids.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Vapor phase is always more of volatile components. Liquid phase is always more of high boiling point liquids.

8. _____ gives the relationship between the concentration of gas entering stage n and concentration of liquid leaving stage n.
a) Equilibrium curve
b) Operating line
c) Equilibrium line
d) None of the mentioned

View Answer

Answer: b [Reason:] Operating line gives the relationship between the concentration of gas entering stage n and concentration of liquid leaving stage n.

9. Which of the following statements is correct with respect to gas absorption?
a) Sufficient contact time plays an important role in absorption
b) Adequate contact area plays an important role in absorption
c) Contact time becomes irrelevant after equilibrium and only the interfacial area plays a crucial role
d) All of the mentioned

View Answer

Answer: d [Reason:] Sufficient contact time and adequate contact area play an important role in absorption. But, contact time becomes irrelevant after equilibrium and only the interfacial area plays a crucial role.

10. Statement 1: Packed towers are used for physical absorption.
Statement 2: Agitated vessels are used for physical absorption.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: a [Reason:] Packed towers are used for physical absorption. Agitated vessels are used for chemical absorption.

11. To increase the solubility of carbon-di-oxide in coke, it is subjected to high pressure.
a) True
b) False

View Answer

Answer: a [Reason:] To increase the solubility of carbon-di-oxide or other gases in aerated drinks, it is subjected to high pressure.

12. How does the solubility of carbon-di-oxide in coke increase when it is subjected to high pressure?
a) Interfacial area increases
b) Pressure drop decreases
c) It shifts the equilibrium to a higher side
d) All of the mentioned

View Answer

Answer: c [Reason:] The solubility of carbon-di-oxide in coke increase when it is subjected to high pressure as it shifts the equilibrium to a higher side and mass transfer takes place till equilibrium is established.

13. Which of the following is true about an agitator vessel?
a) Small bubbles have a high interfacial area
b) Bubbles in an agitator vessel are small
c) Small bubbles have a lower rise velocity
d) All of the mentioned

View Answer

Answer: d [Reason:] Bubbles in an agitator vessel are small. Small bubbles have a high interfacial area and a low rise velocity.

14. Agitator vessels are taller than bubble columns.
a) True
b) False

View Answer

Answer: b [Reason:] Agitator vessels are shorter than bubble columns because they’ve mechanical agitation. Also, they’ve small bubble sizes which have a low rise velocity and hence more contact time is available.

15. Extremely small packing is favorable for packed towers as the surface area increases.
a) True
b) False

View Answer

Answer: b [Reason:] With the decrease in the size of the packing, the pressure drop increases, hence, extremely small packing is not ideal. An optimum size needs to be calculated.

Set 4

1. Statement 1: Evaporation is considered a mass and heat transfer operation.
Statement 2: After evaporation, solids are left behind.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: c [Reason:] Evaporation is considered as a pure heat transfer operation. After evaporation, solvent is left behind.

2. During evaporation of edible solutions, the BPR-boiling point rise should be _____ and the foaming and scale formation should be _____
a) Low, minimum
b) High, maximum
c) Low, maximum
d) High, minimum

View Answer

Answer: a [Reason:] During evaporation of edible solutions, the BPR-boiling point rise should be low and the foaming and scale formation should be minimum.

3. Which of the following is true while concentrating jams?
a) They’re sensitive to heat
b) Evaporation process for jams is carried out under vacuum
c) At vacuum, the boiling point decreases
d) All of the mentioned

View Answer

Answer: d [Reason:] All the given statements with respect to jams are true.

4. Statement 1: Boiling point rise is due to the colligative properties due to the presence of solid particles in the solvent.
Statement 2: Boiling point rise is due to the increase in pressure at the bottom of the solvent due to hydro-static head of the column.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Boiling point rise maybe due to both of the above mentioned reasons.

5. Statement 1: Duhring’s rule states that the ratio of temperatures at which two solutions have the same vapor pressure is a constant.
Statement 2: Duhring’s rule states that the boiling point of a solution is a linear function of the boiling point of pure water at the same pressure.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Both the statements are true. Duhring’s rule is stated in both the ways.

6. Statement 1: In a multiple effect evaporator, the overall temperature drop is equal to the individual drops at each step.
Statement 2: In a multiple effect evaporator, the total area is equal to the sum of the individual areas.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: c [Reason:] In a multiple effect evaporator, the total temperature drop is equal to the sum of the individual temperatures at each step. In a multiple effect evaporator, the total area is equal to the individual areas at each step.

7. Statement 1: Forward feeding requires pumps for the feed at every step.
Statement 2: In a backward feeding arrangement, the most concentrated feed is exposed to the maximum steam in order to remove heat. This is its advantage.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: d [Reason:] Backward feeding arrangement requires pumps for the feed at every step.

8. One disadvantage with backward feeding is that the feed gets very concentrated at the beginning few units itself and hence it’s difficult to feed it to the next evaporator unit.
a) True
b) False

View Answer

Answer: b [Reason:] One disadvantage with forward feeding is that the feed gets very concentrated at the beginning few units itself (due to direct steam supply with provides high heat) and hence it’s difficult to feed it to the next evaporator unit.

9. Mixed feed arrangement offers the advantage of omitting the usage of pumps by transferring feed in the direction of low pressure. That’s an advantage taken from forward feeding arrangement.
a) True
b) False

View Answer

Answer: a [Reason:] Mixed feed arrangement offers the advantage of omitting the usage of pumps by transferring feed in the direction of low pressure. That’s an advantage taken from forward feeding arrangement.

10. At a food processing industry, the steam was re-compressed and a small amount of steam at high pressures and temperatures was sent into the next evaporation chamber in a multiple effect evaporator. Which of the following is true with respect to the above sentences?
a) There might be wear and tear in the evaporator
b) The overall pressure and temperature of steam increases which is desired
c) The capacity of the evaporator increases
d) All of the mentioned

View Answer

Answer: d [Reason:] The overall pressure and temperature of steam increases which is desired and the capacity of the evaporator increases but there might be wear and tear in the evaporator.

Set 5

1. Liquid-liquid extraction is called leaching.
a) True
b) False

View Answer

Answer: b [Reason:] Solid-liquid extraction is called leaching.

2. If extraction is done at the _____ of the solvent, it is called _____
a) Melting point, decoction
b) Boiling point, decoction
c) Melting point, leaching
d) Boiling point, leaching

View Answer

Answer: b [Reason:] If extraction is done at the boiling point of the solvent, it is called decoction.

3. Statement 1: Soya bean has a high oil content.
Statement 2: If the oil content is high, extraction is done by solvent extraction alone.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: c [Reason:] Soya bean has low oil content. If the oil content is low, extraction is done by solvent extraction alone.

4. Oil seed cakes are obtained by _____
a) Solvent extraction
b) Mechanical pressing
c) None of the mentioned
d) Both of the mentioned

View Answer

Answer: b [Reason:] Oil seed cakes are obtained by mechanical pressing.

5. Statement 1: Partition coefficient pertains to solid-liquid extraction.
Statement 2: Leaching involves both heat and mass transfer.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: c [Reason:] Partition coefficient pertains to liquid-liquid extraction. Leaching involves mass transfer.

6. Which among the following factors does NOT affect extraction?
a) Solubility of solute in the solvent
b) Degree of agitation
c) Concentration difference
d) None of the mentioned

View Answer

Answer: d [Reason:] All the given factors affect extraction.

7. Multi-stage counter-current extraction is expensive as more extractors are needed to strip the solid off the solvent.
a) True
b) False

View Answer

Answer: a [Reason:] Multi-stage counter-current extraction is expensive as more extractors are needed to strip the solid off the solvent.

8. Statement 1: Multi-stage cross-current extraction – the solids contain some amount of solute after every extraction.
Statement 2: Single-stage batch extractor – Used in labs and not on large scale as solvent is continuously subjected to heat.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: c [Reason:] Single-stage batch extractor – the solids contain some amount of solute after every extraction. Multi-stage cross-current extraction – Used in labs and not on large scale as solvent is continuously subjected to heat.

9. _____ is the diagonal of the x-y diagram.
a) Operating line
b) Equilibrium line
c) Equilibrium curve
d) None of the mentioned

View Answer

Answer: b [Reason:] Equilibrium line is the diagonal of the x-y diagram.

10. Statement 1: In counter-current extraction, equilibrium is reached at every stage.
Statement 2: Right angled triangle method also called as difference point method is used to calculate the ideal number of stages for extraction.
a) True, False
b) True, True
c) False, False
d) False, True

View Answer

Answer: b [Reason:] Both statements are true. In counter-current extraction, equilibrium is reached at every stage. Right angled triangle method also called as difference point method is used to calculate the ideal number of stages for extraction.

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