Asked by Megan
I have this awful problem due tomorrow; if anyone can help it would be much appreciated.
Most introductory chemistry texts provide a formula for the freezing point depression/boiling point of elevations:
delta-T(f,b)= K(f,b) * m
(m = molality)
In fact, these are derived equations for dilute solutions. They are generated from the more general relationships....
ln Xsolv= delta-b/R [(1/T) - (1/Tb)]
-ln Xsolv= delta-Hf/R [(1/T) - (1/Tf)]
Please derive the latter from the former for boiling point elevation, and indicate which values are contained in the super-constant Kb. (This is a difficult derivation; you'll find some assumptions are made based on the fact that the solution is dilute.)
Two question first on just what's being asked:
1. I'm going to start with the first equation and end up with one of the next two, correct?
2. What does it mean "Indicate which values are contained in the super-constant Kb"?
Here are my thoughts so far, looking just at the variables in both equations:
I know that...
ln P2/P1= delta-Hfusion/R [(1/T2)-(1/T1)]
dT/dP= delta-Hfusion/T [V1 - V2]
Μu(i)= Μu°i + RT ln a(i)
And in dilute systems a(i) --> 1
P(i)= Xi*P°i
P(t)= XB(P°B - P°A) + P°A
I looked through my worksheets and tried to pull out anything that looked useful, but I'm not sure how to piece it all together. Any help would be much appreciated.
Most introductory chemistry texts provide a formula for the freezing point depression/boiling point of elevations:
delta-T(f,b)= K(f,b) * m
(m = molality)
In fact, these are derived equations for dilute solutions. They are generated from the more general relationships....
ln Xsolv= delta-b/R [(1/T) - (1/Tb)]
-ln Xsolv= delta-Hf/R [(1/T) - (1/Tf)]
Please derive the latter from the former for boiling point elevation, and indicate which values are contained in the super-constant Kb. (This is a difficult derivation; you'll find some assumptions are made based on the fact that the solution is dilute.)
Two question first on just what's being asked:
1. I'm going to start with the first equation and end up with one of the next two, correct?
2. What does it mean "Indicate which values are contained in the super-constant Kb"?
Here are my thoughts so far, looking just at the variables in both equations:
I know that...
ln P2/P1= delta-Hfusion/R [(1/T2)-(1/T1)]
dT/dP= delta-Hfusion/T [V1 - V2]
Μu(i)= Μu°i + RT ln a(i)
And in dilute systems a(i) --> 1
P(i)= Xi*P°i
P(t)= XB(P°B - P°A) + P°A
I looked through my worksheets and tried to pull out anything that looked useful, but I'm not sure how to piece it all together. Any help would be much appreciated.