Please help I\'m a bit confused on this Q1) please explain the distribution coef
ID: 845762 • Letter: P
Question
Please help I'm a bit confused on this
Q1) please explain the distribution coefficient.
Q2) Linus and Niels need to extract organic chemical A from water to methylene chloride. They both have 75mg of A dissolved in 2mL of water. They are allowed to use 3mL of methylene chloride to extract A. Linus adds the 3mL of methylene chloride in one portion to the aqueous solution, shakes, removes the organic layer and evaporates the solvent away. Niels performs two successive extractions with 1.5mL of methylene chloride each time. He shakes each one, removes the organic layer each time, combines them and evaporates the solvent away. Which student will have a greater recovery of compound A? Why? If compound A has a distribution coefficient of 10 then how much did each student recover?
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Thank you for the help
Explanation / Answer
Distribution Coefficient If a solute is introduced into any two phase system which may be gas/solid, gas/liquid, liquid/liquid or liquid/solid, it will become distributed between the two phases and, when equilibrium is reached, the solute distribution will be defined by the distribution coefficient. The distribution coefficient of a solute between two phases is calculated as the ratio of the concentration of the solute in one phase to the concentration of the solute in the other phase under equilibrium conditions. Either phase may be used as the reference phase, but in chromatography, the distribution coefficient is always referred to the stationary phase (i.e. the ratio of the concentration of the solute in the stationary phase to that in the mobile phase). The concentration may be taken as mass per unit volume in both phases (which is the most usual) or the mass per unit mass in both phases which is sometime employed in gas solid chromatography. The distribution coefficient is temperature dependant.
Well let's take an example that we have an a container with both oil and water in it these are inmiscible, know, let's say there is elemental iodine I2 in this container, iodine is nonpolar, so there will be more dissolved in the oil (an organic non polar solvent) than the water (a nonorganic polar solvernt). However, there will be a trace amount of iodine dissolved in the water. The distribution coefficient for this oil, we will say equals K. K=(concentration in mol/L of I2 in oil)/(concentration in mol/L of I2 in water) The distribution constant describes thr ration of iodine concentration in the organic layer to that in water.