How do you calculate the osmolarity of seawater?
You add up the molarities of the constituent ions.
The composition of seawater varies around the world, but the concentrations of the six most abundant ions in a "typical" sample are:
Thus, if you consider just the
If you include the magnesium, calcium, potassium, and sulfate ions, the osmolarity is closer to 1200 mOsmol/L.