Finals (Sepa) Mulcho

b

Which of the following statements about absorption is correct?

A. Absorption is the process of transferring a solute from a gas phase to a solid phase.

B. Absorption is the process of transferring a solute from a gas phase to a liquid phase.

C. Absorption is the process of transferring a solute from a liquid phase to a gas phase.

D. Absorption is the process of transferring a solute from a liquid phase to a solid phase.

d

In an absorption process, the term "loading" refers to:

A. The amount of solvent used per unit of gas treated.

B. The concentration of solute in the gas phase.

C. The concentration of solute in the liquid phase.

D. The amount of solute absorbed per unit volume of absorbent.

c

What is the primary driving force for mass transfer in absorption?

A. Temperature gradient

B. Pressure gradient

C. Concentration gradient

D. Volumetric flow rate

d

Which of the following is NOT a common solvent used in gas absorption processes?

A. Water

B. Organic solvents

C. Aqueous solutions of acids or bases

D. Metallic solvents

b

Stripping is best defined as:

A. The removal of solvent from a solute.

B. The removal of solute from a liquid mixture by a gas phase.

C. The removal of solute from a gas mixture by a liquid phase.

D. The removal of solvent from a liquid mixture by a solid phase.

c

In stripping operations, the key parameter to control is:

A. Temperature of the liquid phase.

B. Pressure of the gas phase.

C. Flow rate of the stripping gas.

D. Concentration of solute in the liquid phase.

a

Which of the following equations represents the material balance for an absorption process in steady-state conditions?

A. FyF +SxS = VyV + LxL

B. FyF = VyV

C. FyF = SxS

D. FyF +VyV = LxL

b

The Kremser equation is used to calculate:

A. The height of the absorption column.

B. The number of theoretical stages in an absorption or stripping process.

C. The flow rate of the absorbent.

D. The pressure drop across the absorption column.

b

The term "operating line" in the context of absorption refers to:

A. A line that represents the equilibrium stages in a McCabe-Thiele diagram.

B. A line that represents the mass balance in the absorption column.

C. A line that represents the concentration of the solvent.

D. A line that represents the temperature profile along the column.

d

Which of the following factors does NOT affect the efficiency of an absorption process?

A. Solubility of the gas in the liquid.

B. Temperature of the liquid phase.

C. Flow rate of the gas phase.

D. Color of the absorbent.

b

In a ternary liquid-liquid extraction system, which component is usually the solute?

A. Component present in the highest concentration.

B. Component that is to be extracted.

C. Component that acts as the solvent.

D. Component that acts as the raffinate.

c

The term "tie line" in the context of ternary liquid-liquid extraction refers to:

A. Line connecting points of equal solute concentration.

B. Line connecting initial & final solute concentrations.

C. Line connecting compositions of coexisting phases.

D. Line indicating the path of extraction efficiency.

b

Which of the following best describes the role of a solvent in liquid-liquid extraction?

A. It increases the pressure of the system.

B. It selectively dissolves one or more components from a liquid mixture.

C. It reacts chemically with the solute to form a new compound.

D. It decreases the temperature of the system.

c

In a ternary phase diagram, the plait point is:

A. The point where the feed mixture is introduced.

B. The point where the solvent and raffinate compositions are equal.

C. The point where the two liquid phases become identical.

D. The point where the extract and raffinate phases intersect.

b

The distribution coefficient (K) in liquid-liquid extraction is defined as:

A. The ratio of the mass of solute in the extract phase to the mass of solute in the raffinate phase.

B. The ratio of the concentration of solute in the extract phase to the concentration of solute in the raffinate phase.

C. The ratio of the flow rate of the extract phase to the flow rate of the raffinate phase.

D. The ratio of the volume of the extract phase to the volume of the raffinate phase.

b

In a ternary liquid-liquid extraction system, which component is usually the solute?

A. The component present in the highest concentration.

B. The component that is to be extracted.

C. The component that acts as the solvent.

D. The component that acts as the raffinate.

c

The term "tie line" in the context of ternary liquid-liquid extraction refers to:

A. A line connecting points of equal solute concentration.

B. A line connecting the initial and final concentrations of a solute.

C. A line connecting the compositions of coexisting phases in equilibrium.

D. A line indicating the path of extraction efficiency.

b

18. Which of the following best describes the role of a solvent in liquid-liquid extraction?

A. It increases the pressure of the system.

B. It selectively dissolves one or more components from a liquid mixture.

C. It reacts chemically with the solute to form a new compound.

D. It decreases the temperature of the system.

c

19. In a ternary phase diagram, the plait point is:

A. The point where the feed mixture is introduced.

B. The point where the solvent and raffinate compositions are equal.

C. The point where the two liquid phases become identical.

D. The point where the extract and raffinate phases intersect.

b

The distribution coefficient (K) in liquid-liquid extraction is defined as:

A. The ratio of the mass of solute in the extract phase to the mass of solute in the raffinate phase.

B. The ratio of the concentration of solute in the extract phase to the concentration of solute in the raffinate phase.

C. The ratio of the flow rate of the extract phase to the flow rate of the raffinate phase.

D. The ratio of the volume of the extract phase to the volume of the raffinate phase.

d

When designing an absorption column for a gas-liquid system, which parameter is most critical in determining the column

diameter?

A. The solubility of the gas in the liquid.

B. The liquid-to-gas ratio (L/G).

C. The vapor pressure of the liquid phase.

D. The flooding velocity of the gas phase.

c

In the design of a packed absorption column, which factor primarily influences the height of the packing required to achieve a

given separation?

A. The density of the packing material.

B. The pressure drop across the column.

C. The height equivalent to a theoretical plate (HETP).

D. The diameter of the column.

a

For a counter-current absorption column operating at steady-state, which of the following relationships correctly represents the

mass transfer balance for a differential section of the column?

A. d(Gy) = −KG ∝ (y −y∗)dz

B. d(Lx) = KL ∝ (x − x∗)dz

C. d(Gy) = KL ∝ (y − y∗)dz

D. d(Lx) = −KG ∝ (y − y∗)dz

c

When considering the effect of temperature on the design of an absorption column, which statement is most accurate?

A. Increasing the temperature generally increases the solubility of the gas in the liquid, thus reducing the column height

required.

B. Decreasing the temperature typically decreases the gas phase mass transfer coefficient, thus increasing the column diameter.

C. Increasing the temperature typically decreases the solubility of the gas in the liquid, requiring a taller column.

D. The temperature has no significant effect on the solubility of the gas in the liquid or the column design.

c

When designing a liquid-liquid extraction column, which parameter is most critical in determining the column diameter?

A. The interfacial tension between the two liquid phases.

B. The density difference between the two phases.

C. The volumetric flow rate of the dispersed phase.

D. The solubility of the solute in the solvent.

d

In a liquid-liquid extraction column, the term "height equivalent to a theoretical stage" (HETS) is used to:

A. Measure the diameter of the column.

B. Determine the number of theoretical stages required.

C. Calculate the pressure drop across the column.

D. Assess the efficiency of mass transfer.

a

For a counter-current liquid-liquid extraction process, which of the following best describes the effect of increasing the solvent-

to-feed ratio on the design of the extraction column?

A. It decreases the number of theoretical stages required.

B. It increases the height of the extraction column.

C. It has no effect on the column design.

D. It decreases the diameter of the column.

a

In the design of a mixer-settler extraction system, the primary purpose of the mixer is to:

A. Provide intimate contact between the two liquid phases.

B. Separate the two liquid phases.

C. Increase the pressure of the system.

D. Decrease the temperature of the system.

d

Which of the following factors has the least impact on the design of a liquid-liquid extraction column?

A. The solute distribution coefficient.

B. The interfacial tension between the phases.

C. The viscosity of the continuous phase.

D. The color of the solvent.

b

In a liquid-liquid extraction process, which criterion is most important for selecting the solvent?

A. High volatility.

B. High solute selectivity.

C. Low cost.

D. High viscosity.

a

In the design of a centrifugal extractor, the separation efficiency is primarily influenced by:

A. The rotational speed of the centrifuge.

B. The temperature of the feed mixture.

C. The density difference between the two phases.

D. The solubility of the solute in the solvent.

b

When designing a liquid-liquid extraction column, the term "solvent flooding" refers to:

A. The condition where the solvent flow rate is too low to achieve adequate extraction.

B. The condition where the solvent flow rate is too high, causing phase separation to be disrupted.

C. The point where the solvent completely displaces the feed phase.

D. The maximum capacity of the column for handling the solvent.

b

Which factor is most critical in determining the design of the leaching equipment for solid-liquid extraction?

A. Solubility of the solid in the solvent.

B. Particle size distribution of the solid.

C. Color of the solvent.

D. Density of the solid.

b

In leaching equipment design, the term "residence time" refers to:

A. The time required for complete dissolution of the solute.

B. The time the solvent and solid remain in contact.

C. The time taken for the solvent to evaporate.

D. The time required for the solute to crystallize.

c

Which type of leaching equipment is best suited for handling large quantities of ore with high extraction efficiency?

A. Batch leaching tank

B. Continuous stirred tank reactor (CSTR)

C. Percolation leaching system

D. Rotary drum extractor

c

In the design of a washing system, which parameter is most critical for achieving efficient washing?

A. Temperature of the washing fluid

B. Viscosity of the washing fluid

C. Flow rate of the washing fluid

D. Pressure of the washing fluid

d

When designing a leaching operation, the selection of the solvent is critical. Which of the following characteristics is least

important in solvent selection?

A. High solubility for the target solute.

B. Low cost.

C. Low toxicity.

D. High viscosity.

b

The design of leaching equipment often includes the calculation of the "number of extraction stages." Which factor primarily

influences this calculation?

A. The density of the solvent.

B. The distribution coefficient of the solute.

C. The color of the solid.

D. The temperature of the solvent.

a

In a counter-current washing operation, increasing the number of washing stages will:

A. Decrease the amount of solvent required.

B. Increase the concentration of impurities in the solid.

C. Increase the amount of solvent required.

D. Decrease the efficiency of washing.

b

Which of the following best describes the "heap leaching" process used in industrial applications?

A. A process where the solid is continuously stirred in a solvent.

B. A process where the solid is placed in a pile and the solvent percolates through the pile.

C. A process where the solid is dissolved in a high-pressure reactor.

D. A process where the solid and solvent are mixed in a rotary drum.

c

In liquid-liquid extraction involving ternary systems, what is the primary purpose of the solvent?

A) To dissolve the feed components

B) To act as a catalyst

C) To selectively dissolve one or more components from the feed

D) To neutralize the feed components

c

The selection of a suitable solvent for liquid-liquid extraction is based on which key property?

A) High viscosity

B) High boiling point

C) High selectivity and solubility for the solute

D) High density

a

In a ternary phase diagram for liquid-liquid extraction, the plait point represents:

A) The composition at which the two liquid phases become identical

B) The maximum solubility of the solute in the solvent

C) The point where the feed composition equals the solvent composition

D) The intersection of the tie lines

c

Which of the following is a characteristic of a good extraction solvent in ternary systems?

A) Low solubility in the raffinate phase

B) High miscibility with the feed

C) High solubility in the extract phase

D) Low density compared to the solute

b

In liquid-liquid extraction with ternary systems, the term "tie line" refers to:

A) The line connecting the feed composition to the solvent composition

B) The line connecting the equilibrium compositions of the two coexisting phases

C) The line representing the phase boundary

D) The line indicating the solubility limit of the solute

c

The lever rule in the context of ternary liquid-liquid extraction systems is used to determine:

A) The boiling point of the mixture

B) The distribution coefficient

C) The relative amounts of the coexisting phases

D) The density of the extract phase

c

In liquid-liquid extraction, the efficiency of separation is improved by:

A) Increasing the solute concentration in the feed

B) Decreasing the temperature of the system

C) Using a solvent with higher selectivity for the solute

D) Increasing the mixing time

a

In leaching, the purpose of the solvent is to:

A) Extract soluble components from the solid matrix

B) React chemically with the solute

C) Dissolve the entire solid matrix

D) Precipitate the solute out of solution

c

Which factor primarily affects the rate of leaching?

A) The boiling point of the solvent

B) The color of the solid matrix

C) The surface area of the solid particles

D) The pH of the solvent

b

In a typical leaching process, increasing the temperature generally:

A) Decreases the solubility of the solute

B) Increases the solubility of the solute

C) Has no effect on the solubility

D) Decreases the leaching rate

d

The efficiency of leaching can be improved by:

A) Using a solvent with a low density

B) Reducing the agitation speed

C) Using a solvent that forms a precipitate with the solute

D) Increasing the solvent-to-solid ratio

a

In countercurrent leaching, the solute concentration in the solvent:

A) Increases as the solvent moves through the leaching stages

B) Is lower in the final solvent stream than in the initial stream

C) Remains constant throughout the process

D) Decreases as the solvent moves through the leaching stages

c

The primary goal of washing in a leaching process is to:

A) Increase the particle size of the solid matrix

B) Separate the solvent from the solute

C) Remove residual solute from the solid matrix

D) Decrease the temperature of the leachate

c

In solid-liquid extraction, the distribution coefficient (Kd) is defined as:

A) ratio of solute concentration in the solid to that in liquid

B) ratio of solvent volume to solid mass

C) ratio of solute concentration in the liquid to that in solid

D) ratio of solvent density to solute density

d

Which of the following is a key consideration when selecting a solvent for leaching?

A) High viscosity

B) High boiling point

C) High vapor pressure

D) High selectivity for the solute