Partition Coefficient and Retardation Factor

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The discussion revolves around calculating the retardation factor (Rd) and partition coefficients (Kd and Koc) for solutes based on given equations and data. The user successfully calculated Koc using the log equation and derived Kd, but struggles with conceptual questions regarding the relationship between coefficients and a provided graph. They believe that solute C has the highest partition coefficient and solute A the lowest, based on their dissolution rates. For Part B, the user attempted to derive Rd for solute B by comparing the time taken by solutes A and B but is uncertain about the correctness of their method and the relevance of the 20 cm length mentioned in the problem. Overall, the user seeks clarification on their calculations and conceptual understanding of the retardation factor and partition coefficients.
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Homework Statement



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Homework Equations



Rd = retardation factor = (1 + (ƥbKd / n))

log(Koc) = -0.55logS + 3.64

Kd = Koc*foc

The Attempt at a Solution



Part C is the only part I feel sure on. I simply plugged 1480 mg/L into the log(Koc) equation above to solve for Koc. Then I multiplied Koc by the foc given in the problem statement to obtain Kd. Finally, I plugged Kd in the Rd equation above along with the bulk density of the soil and the soil porosity given, and solved. Seems straight forward enough.

Part A is simply a concept-type question, but I do not know how to relate coefficients to this type of graph shown. Since there is no textbook for the class, I have no way to confirm if I'm right or not in my current thinking. I answered that the partition coefficient would be biggest for solute C and smallest for solute A, because a small partition coefficient would imply it dissolves in water more easily, shown by the graph for solute A reaching equilibrium the quickest. Am I correct here?

Part B is the oddest for me. At first I thought it was giving me the Rd of solute A so that I could plug in and solve for Kd, then use that Kd for the solute B to solve for its Rd. However, plugging in 1 for Rd gives a Kd of 0, so it must not be the right method. So, I simply compared the times it took solute A and solute B, and multiplied solute A's Rd by the same factor. So since 3.5 hours is 1.75x more than 2 hours, I did (1 * 1.75) = 1.75 for the Rd of solute B. I'm sure this method is totally wrong, but I have no references to find the right way, so any help would be much appreciated.

One thing that immediately let's me know I'm wrong somewhere is that I never used the 20 cm length given in the problem statement. Is this somehow used to find solute B's Rd?
 
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