Question:
In liquid-liquid extraction, the distribution coefficient D is defined as:
In liquid-liquid extraction, the distribution coefficient D is defined as:
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Always remember that distribution coefficients are temperature-dependent.
Operating temperature must be maintained constant during extraction to ensure stable and predictable distribution behaviour.
Operating temperature must be maintained constant during extraction to ensure stable and predictable distribution behaviour.
Updated On: Jul 3, 2026
- Concentration in extract / Concentration in raffinate
- Concentration in feed / Concentration in solvent
- Mole fraction in heavy phase / light phase
- Activity coefficient ratio
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the thermodynamic definition of the distribution coefficient (or partition coefficient, \( D \)) in liquid-liquid extraction.
Step 2: Key Formula or Approach:
Liquid-liquid extraction involves separating a solute from a liquid feed by contacting it with an immiscible solvent phase.
At equilibrium, the solute distributes itself between the two phases (the solvent-rich extract phase and the diluent-rich raffinate phase) according to the distribution coefficient:
\[ D = \frac{C_E}{C_R} \]
where \( C_E \) is the solute concentration in the extract phase, and \( C_R \) is the solute concentration in the raffinate phase.
Step 3: Detailed Explanation:
• Extract Phase: The phase containing the solvent and the extracted solute.
• Raffinate Phase: The residual liquid feed phase from which the solute has been removed.
• Distribution Coefficient Significance: The value of \( D \) measures the solvent's affinity for the solute.
A high distribution coefficient (\( D \gt 1 \)) is desirable because it means less solvent is required to achieve a specified separation.
If \( D \lt 1 \), the solute has a higher affinity for the feed diluent, making extraction difficult.
• Selectivity comparison: The separation efficiency is also governed by selectivity (\( \beta \)), which is the ratio of the distribution coefficient of the solute to that of the diluent.
Step 4: Final Answer:
The distribution coefficient is defined as the concentration of solute in the extract phase divided by the concentration of solute in the raffinate phase.
The question asks for the thermodynamic definition of the distribution coefficient (or partition coefficient, \( D \)) in liquid-liquid extraction.
Step 2: Key Formula or Approach:
Liquid-liquid extraction involves separating a solute from a liquid feed by contacting it with an immiscible solvent phase.
At equilibrium, the solute distributes itself between the two phases (the solvent-rich extract phase and the diluent-rich raffinate phase) according to the distribution coefficient:
\[ D = \frac{C_E}{C_R} \]
where \( C_E \) is the solute concentration in the extract phase, and \( C_R \) is the solute concentration in the raffinate phase.
Step 3: Detailed Explanation:
• Extract Phase: The phase containing the solvent and the extracted solute.
• Raffinate Phase: The residual liquid feed phase from which the solute has been removed.
• Distribution Coefficient Significance: The value of \( D \) measures the solvent's affinity for the solute.
A high distribution coefficient (\( D \gt 1 \)) is desirable because it means less solvent is required to achieve a specified separation.
If \( D \lt 1 \), the solute has a higher affinity for the feed diluent, making extraction difficult.
• Selectivity comparison: The separation efficiency is also governed by selectivity (\( \beta \)), which is the ratio of the distribution coefficient of the solute to that of the diluent.
Step 4: Final Answer:
The distribution coefficient is defined as the concentration of solute in the extract phase divided by the concentration of solute in the raffinate phase.
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