Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Relative osmotic pressure is the pressure required to stop the net flow of solvent molecules through a semipermeable membrane when compared between two solutions. It reflects the difference in solute concentration across the membrane.
Osmotic pressure depends on the solute concentration; higher solute concentrations result in higher osmotic pressures.
Relative osmotic pressure can be measured using van't Hoff's law: $\Pi = iMRT$, where $\Pi$ is osmotic pressure, $i$ is the ionization constant, $M$ is molarity, $R$ is the gas constant, and $T$ is temperature.
It plays a critical role in biological systems, helping to maintain proper cell function and volume.
In medical applications, relative osmotic pressure is crucial for processes like dialysis and intravenous fluid administration.
Differences in relative osmotic pressure can lead to osmosis, causing water to move from areas of low solute concentration to high solute concentration.