# Answer to Question #32065 in Physical Chemistry for Luis Tudayan

Question #32065
The freezing point of blood serum is about - 0.56 deg C. What is its osmotic pressure at 37 deg C?
1
2013-06-21T10:45:52-0400
Freezingpoint depression is given by:
&Delta;T = Kf&middot;i&middot;m
where
Kf cryoscopic constant of solvent Kf = 1.86Kkg/mol
i van't Hoff factor of solute.
m Molality = mole solute / kg solvent

Osmotic pressurie point depression is given by:
&pi; = i&middot;c&middot;R&middot;T
where
i van't Hoff factor of solute.
c Molarity = mole solute / m&sup3; solution
R universal gas constant
T absolute temperature in K

Assume that
1. van't Hoff factors does not change between -0.56&deg;C and 37&deg;C
2. volumes of solution is equal to the volumes of solvent contained of
solution.

Then you can calculate the molarity from multiplying by pure water
density.
c = m &middot;&rho;w
(at 37&deg;C &rho;w = 994kg/m&sup3;)

Solve freezing point equation for molality
m = &Delta;T/(Kf&middot;i)

=&gt;
c = [&Delta;T/( Kf&middot;i)] &middot; &rho;w

=&gt;
&pi; = i &middot; [&Delta;T/( Kf&middot;i) ] &middot;&rho;w &middot; R &middot; T = [&Delta;T/Kf] &middot;&rho;w &middot; R &middot; T = [0.56K / 1.86Kkg/mol ] &middot; 994kg/m&sup3; &middot; 8.314472J/mol K &middot; 310K = 771361.3 Pa = 7.613atm

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Assignment Expert
07.08.13, 17:27