Number of extractions (n) - LLE

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In summary, the distribution constant of stearic acid between n-heptane and acetic acid is 4.95 at 25 °C. To reduce the residual content of stearic acid in the acetic acid layer to 0.08% of its original value, multiple extractions with equal volumes of n-heptane are necessary. The original amount of stearic acid remaining in the acetic acid after a single extraction is approximately 0.92%. However, this calculation may not be accurate without further information and clarification on relevant equations and definitions.
  • #1
il postino
31
7
Homework Statement
Determine the number of extractions from a solution
Relevant Equations
ni (alfa) = ni . f^n
Hi all!
The distribution constant of stearic acid between n-heptane and acetic acid is 4.95 at
25 ° C. Determine the number of extractions from a solution of stearic acid in acid
acetic acid, with successive portions of n-heptane of equal volume to the solution, necessary
to reduce the residual content of stearic acid in the acetic acid layer to 0.08% of
its original value.I don't know where to start, could you help me?
 
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  • #2
How much original stearic acid (what fraction of it) is left in the acetic acid after a single extraction?
 
  • #3
[QUOTE = "Borek, publicación: 6389436, miembro: 23711"]
¿Cuánto ácido esteárico original (qué fracción) queda en el ácido acético después de una única extracción?
[/ CITAR]

0.92%?
 
  • #4
Show how you got this number (doesn't look right to me).
 
  • #5
And your relevant equations are pretty unhelpful. If you wrote out the definition of distribution constant, and defined what symbols mean you would be most of the way to solving the problem.
 

1. What is the purpose of determining the number of extractions in liquid-liquid extraction (LLE)?

The number of extractions in LLE is used to determine the efficiency of the extraction process and to optimize the amount of solvent needed for a desired level of separation. It also helps in predicting the number of extraction steps required to achieve a desired degree of separation.

2. How is the number of extractions calculated in LLE?

The number of extractions (n) in LLE is calculated using the equation n = log(Co/Cf) / log(R), where Co is the initial concentration of the solute in the aqueous phase, Cf is the final concentration of the solute in the aqueous phase, and R is the distribution coefficient of the solute between the two phases.

3. What factors affect the number of extractions in LLE?

The number of extractions in LLE is affected by several factors, such as the distribution coefficient, the initial and final concentrations of the solute, the volume of the solvent, and the efficiency of the mixing and separation processes. The choice of solvent and the pH of the aqueous phase can also impact the number of extractions.

4. How does the number of extractions affect the overall efficiency of LLE?

The number of extractions in LLE is directly related to the efficiency of the process. A higher number of extractions can lead to a more thorough separation of the solutes, but it also requires more time and resources. On the other hand, a lower number of extractions may not achieve the desired level of separation. Therefore, it is important to optimize the number of extractions for a specific separation process.

5. Can the number of extractions be used to compare the efficiency of different extraction methods?

Yes, the number of extractions can be used to compare the efficiency of different extraction methods, as long as the same solvents and conditions are used. However, it should be noted that the number of extractions is just one factor in determining the efficiency of an extraction process, and other factors such as selectivity and yield should also be considered when comparing different methods.

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