How this calculator works
Use the dilute-solution van t Hoff relation with a separate empirical osmotic coefficient. The concentration is for solute formula units before dissociation. A particle factor of two idealizes complete dissociation into two species; the osmotic coefficient represents additional departures from ideality. Avoid counting the same nonideality in both inputs. Mass mode uses final solution volume.
Formula
Pi = i phi c R T, with c in mol/m3, T in K and Pi in Pa.
Worked example
At 300 K, c = 100 mol/m3, i = 1 and phi = 1 give Pi = 249433.8785445972 Pa. Doubling i doubles the pressure.
Advertisement
Frequently asked questions
Can the particle factor be non-integer?
Yes. An effective measured factor can represent incomplete dissociation.
Is this an osmolality calculation?
No. It uses amount per solution volume, not amount per kilogram of solvent.
Does temperature have to be kelvin?
The calculation uses kelvin; the selector also accepts Celsius and Fahrenheit.