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What is the difference between osmolarity and osmolarity ??
Hossam Elgnainy Selected answer as best April 24, 2025
It looks like you typed the same word twice: osmolarity and osmolarity. Maybe you meant to ask about the difference between:
- Osmolarity and osmolality?
If so, here’s the difference:
- Osmolarity is the number of osmoles of solute per liter of solution (Osm/L).
- Osmolality is the number of osmoles of solute per kilogram of solvent (Osm/kg).
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- Osmolarity depends on volume, which can change with temperature.
- Osmolality depends on mass, which is more stable and accurate, especially in clinical settings (like blood or urine tests).
Hossam Elgnainy Selected answer as best April 24, 2025
1. Osmolarity (in mOsm/L):
Osmolarity = Molarity (mol/L) × Number of particles (n) × 1000
Example: For 0.9% NaCl (0.154 mol/L), which dissociates into 2 particles (Na⁺ and Cl⁻):
Osmolarity = 0.154 × 2 × 1000 = 308 mOsm/L
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2. Osmolality (in mOsm/kg):
Osmolality = Molality (mol/kg) × Number of particles (n)
In clinical settings (plasma osmolality is often estimated by):
Osmolality = (2 × [Na⁺]) + (Glucose / 18) + (BUN / 2.8)
All concentrations in mg/dL
Is the equation used to calculate osmolarity the same used to calculate osmolality ?