Osmotic Pressure — Van't Hoff's Law
Solute particles cross a semipermeable membrane driven by concentration gradients
Setup
Solute concentration (left):
0.7
M
Solute concentration (right):
0.2
M
Temperature T:
298
K
Membrane permeability:
0.5
Reset Particles
Π = cRT
ΔΠ =
--
atm
Van't Hoff (1886):
osmotic pressure Π = cRT, where c is molar concentration, R the gas constant, T temperature.
Water flows through the semipermeable membrane (blue line) to equalize chemical potential. Solute molecules (large colored dots) cannot cross.
Watch the water level change and pressure build!