247.76
kPa
2.4452
atm
1,858.33
mmHg
247.76
kPa
2.4452
atm
1,858.33
mmHg
The Osmotic Pressure Calculator determines the osmotic pressure of a solution using the van't Hoff equation. Osmotic pressure is the minimum pressure needed to prevent the inward flow of solvent across a semipermeable membrane. It is a colligative property that depends on the concentration of solute particles, not their identity.
This concept is critical in biology for understanding water movement across cell membranes, kidney filtration, plant water uptake, and intravenous fluid preparation in medicine.
The calculator uses the van't Hoff equation:
π = i × M × R × T
The result is given in kPa, atm, and mmHg for convenience.
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Results
Glucose does not dissociate (i = 1), so a 0.1 M solution exerts about 248 kPa or 2.45 atm of osmotic pressure.
Inputs
Results
NaCl dissociates into two ions (i = 2). Normal saline at body temperature produces approximately 772 kPa, close to blood osmotic pressure.
The van't Hoff factor (i) represents the number of particles a solute produces when dissolved. For non-electrolytes like glucose or sucrose, i = 1. For NaCl, i = 2 (Na⁺ + Cl⁻). For CaCl₂, i = 3 (Ca²⁺ + 2Cl⁻). Real values may be slightly less than ideal due to ion pairing.
Osmotic pressure drives water movement across biological membranes. It determines cell turgor in plants, controls fluid balance in blood and tissues, governs kidney filtration, and is critical for preparing isotonic IV solutions to prevent cell lysis or crenation.
Osmolarity is the total concentration of solute particles in a solution (measured in osmol/L), while osmotic pressure is the actual pressure exerted by that concentration difference across a membrane. Osmotic pressure depends on osmolarity, temperature, and the van't Hoff equation relates them quantitatively.
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