Chemical Forums
Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: technologist on June 30, 2006, 12:18:50 AM
-
A & B are two completely Miscible Liquids where A is solute & B is solvent.
A has 10% solubility in another solvent C. B & C r completely Immiscible.
Now if I start on 100 Kg solution basis of A & B with 20% concentration of A in B.
100 Kg of solution will have 20 Kg A & 80 Kg B.
Now I add 200 Kg of C in the Solution & mix it thoroughly and then allow to separate out 2 phases.
Question is
What will be the amount of A in B & in C?
I know it depends on Partition Coeff. of A in B & C but that is unknown at this stage.
Next Question.
Suppose whole A i.e. 20 Kg comes in C & I separate B & C (They r Immiscible). Now if I add 20 Kg of B again in 220 Kg of C+A & mix it & separate it again.
Will whole of 20 Kg of A go to B? Bcoz A have very good solubility in B?
Any help & discussion...
-
A & B are two completely Miscible Liquids where A is solute & B is solvent.
A has 10% solubility in another solvent C. B & C r completely Immiscible.
So what you're saying is...that A will dissolve 1/10 as much in C as in B. (Assuming A is 100% soluble in B - because otherwise, it wouldn't be the solute any more, would it?)
Now if I start on 100 Kg solution basis of A & B with 20% concentration of A in B.
100 Kg of solution will have 20 Kg A & 80 Kg B.
Agreed.
Now I add 200 Kg of C in the Solution & mix it thoroughly and then allow to separate out 2 phases.
So now you have 20 kg of A dissolve among 80 kg of B and 200 kg of C.
Question is
What will be the amount of A in B & in C?
C dissolves A one tenth as much as B does. So you need 10 kg of C to dissolve as much A as 1 kg of B. In effect, the 200 kg of C is going to act just like 20 kg of B (20 is one tenth of 200).
Now it's like you have 20 kg of A dissolved among two systems: one with 80 kg of B, one with 20 kg of B. And the concentration of A is going to be the same in each of them...since they're both B (or at least, effectively). So, 80/(80+20) of the A will be dissolved in the REAL B, and 20/(80+20) will be dissolved in the pseudo-B (which is really C).
Hope that helps...maybe it was too confusing...I think it's alright.
I know it depends on Partition Coeff. of A in B & C but that is unknown at this stage.
I think I used partition coefficients without knowing it :P
And the whole second question can be solved similarly to the first one....and sometimes using a variable like x really really helps I find.
Man I hope I'm right on this...
-
Its logical.
But Assumption of 100% Solubiility of A in B is something I am not sure about. Bcoz 80% A + 20% B solution also exist. I mean any no beyond 50% A gives more than 100% Solubiility for A&B solution.
However, I am not clear if C is also there.
-
Is solvent C much more volatile than solvent B?
-
Solvent B is more volatile.
-
If solvent B is more volatile than solvent C, wouldn't it be less energy intensive to distill A from A & B compare to distill A from A & C
-
U r right. But my planning is different to recover it.
Anyway it seems that now I need hands on lab experience to establish the things.
Thanks to all.