Question

calculate the osmotic pressure at 25C across a semipermeable membrane separating seawater (1.14 M total particles) from a .47 M solution of aqueous NaCl.

Answer 1

The osmotic pressure of NaCl solution will be

pi = i X concentration X R X T

R= gas constant = 0.0821 L atm / mol K

T = 298 K

i = Van't hoff factor = 2

c= concentration = 0.47 M

osmotic pressure = 2 X 0.47 X 0.0821 X 298 = 22.998 atm

2) osmotic pressure of sea water will be

pi = concentration X R X T

R= gas constant = 0.0821 L atm / mol K

T = 298 K

c= concentration = 1.14 M

osmotic pressure = 1.14X 0.0821 X 298 = 27.891 atm

So pressure gradient will be = 27.891 - 22.998 = 4.893 atm