Compute van ’t Hoff osmotic pressure from molarity, temperature, and i.
| π (Pa) | – |
Use this calculator for physical chemistry or physiology: a known molarity at a bath temperature, perhaps a salt that splits.
The calculation is π = iCRT with C in mol/L, T in kelvin, R the gas constant, and the result in pascals. The factor 1000 converts mol/L into mol/m³ so that π comes out in Pa. Temperature may be entered in °C or °F. i = 1 for glucose, about 2 for fully dissociated NaCl.
This is the ideal dilute van ’t Hoff law. It does not include osmotic coefficients or a non-ideal virial correction.
C (mol/L): Molarity in mol/L. 0.15 is a rough saline.
Temperature: Solution temperature in °C or °F. Body temperature is 37 °C; lab is often 25 °C.
i: van ’t Hoff factor. 1 for nonelectrolytes, 2 if NaCl fully dissociates.
π (Pa): Osmotic pressure in pascals. Divide by 10⁵ for a bar-scale number; 1 M ideal nonelectrolyte at 25 °C is about 2.48 MPa.
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