# 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?

Expert's answer

Freezingpoint depression is given by:

ΔT = K

where

K

i van't Hoff factor of solute.

m Molality = mole solute / kg solvent

Osmotic pressurie point depression is given by:

π = i·c·R·T

where

i van't Hoff factor of solute.

c Molarity = mole solute / m³ solution

R universal gas constant

T absolute temperature in K

Assume that

1. van't Hoff factors does not change between -0.56°C and 37°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 ·ρ

(at 37°C ρ

Solve freezing point equation for molality

m = ΔT/(K

=>

c = [ΔT/( K

=>

π = i · [ΔT/( K

ΔT = K

_{f}·i·mwhere

K

_{f}cryoscopic constant of solvent K_{f}= 1.86Kkg/moli van't Hoff factor of solute.

m Molality = mole solute / kg solvent

Osmotic pressurie point depression is given by:

π = i·c·R·T

where

i van't Hoff factor of solute.

c Molarity = mole solute / m³ solution

R universal gas constant

T absolute temperature in K

Assume that

1. van't Hoff factors does not change between -0.56°C and 37°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 ·ρ

_{w}(at 37°C ρ

_{w}= 994kg/m^{³})Solve freezing point equation for molality

m = ΔT/(K

_{f}·i)=>

c = [ΔT/( K

_{f}·i)] · ρ_{w}=>

π = i · [ΔT/( K

_{f}·i) ] ·ρw · R · T = [ΔT/K_{f}] ·ρ_{w}· R · T = [0.56K / 1.86Kkg/mol ] · 994kg/m³ · 8.314472J/mol K · 310K = 771361.3 Pa = 7.613atm
## Comments

Assignment Expert07.08.13, 17:27You're welcome. We are glad to be helpful.

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Luis Tudayan21.07.13, 17:14thanks for the answer :>

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