Those fo you who are in fist year at LSOP...

Seeing as Course A exams are starting soon, I was wondering if we could set up like a study group on TSR, so if we were having any difficulties we could just post up on here and help each other out. It should help us all... Anyone interested?

yep we should :yep:

OP

I need help with this question to do with solubilities etc:
If you have plotted a graph of solubility of a drug against concentration of surfactant with given values, how do you find the 'intrinsic solubility' of the drug from the graph? And how do you find the critical micellar concentration of the surfactant from the graph? So confused! (JAN 2008 Question B5)

Reply 3

ahmadjan3

12

shenzys

I need help with this question to do with solubilities etc:
If you have plotted a graph of solubility of a drug against concentration of surfactant with given values, how do you find the 'intrinsic solubility' of the drug from the graph? And how do you find the critical micellar concentration of the surfactant from the graph? So confused! (JAN 2008 Question B5)

sorry dont remember anything as i have not started revising yet :o:

i am screwed :frown:

Reply 4

kiz_m

Intrinsic solubility is defined as the number of moles/L of solute that disolves into solution. I'm 'guessing', so don't take this to be the right answer...

By 'intrinsic solubility of vitalin in water' i think it means, without the addition of surfactant. So you can take that to be the solubilities below the CMC, so '2.4mM'. But 2.4mM = 2.4 mMoles/L, and intrinsic solubility is measured as 'moles/L', so maybe just divide that value by a 1000 to give 0.0024M/L? :confused:

The CMC of the surfactant is the minimum concentration of surfactant at which micelles begin forming, therefore the point at which solubilisation can begin.
If you look at the table provided, it indicates that the solubility of Vitalin doesn't change up until 10mM of surfactant, so this is the 'CMC'. So the question just required you to look at the table, not the graph :smile: