How do you calculate osmolarity from osmolality?

Question

Henry Antrim · Accepted Answer

Consider the definitions...

#"Osmolarity"="Moles of ions in solution"/"Litres of solution"# #"Osmolality"="Moles of ions in solution"/"Kilograms of solvent"# For most DILUTE solutions in WATER, #"Osmolarity"="Osmolality"#...but here we are given no data with respect to the composition of the solutions or their respective densities...so we are in no position to assess the comparison....

Caleb Adams · Answer

undefined To calculate osmolarity from osmolality, you need to know the volume of the solution. Osmolarity is the concentration of a solution expressed in osmoles of solute per liter of solution (osmol/L), while osmolality is the concentration of a solution expressed in osmoles of solute per kilogram of solvent (osmol/kg).

To convert osmolality to osmolarity, you can use the following equation:

$$ Osmolarity = Osmolality \times \frac{\text{Density of the solvent}}{1000} $$

Where:
- Osmolarity is the concentration of the solution in osmoles per liter (osmol/L).
- Osmolality is the concentration of the solution in osmoles per kilogram (osmol/kg).
- Density of the solvent is the density of the solvent in grams per milliliter (g/mL) or kilograms per liter (kg/L).

By multiplying the osmolality by the density of the solvent divided by 1000, you can convert osmolality to osmolarity.