Osmolality and osmolarity are two terms that are used to measure the amount of osmoles of solute present in a kilogram of solvent, and the number of osmoles that 1 liters of a solution contains, respectively. The term that explains the osmotic concentration of a solution is known as osmolarity, and it is expressed as osmoles of solute per liter of solution.
At times, to determine the osmolarity of a solution can be very difficult since its volume is usually affected by any change in temperature and pressure, and it also changes when more solutes are added. Osmolality, on the other hand, is used to determine the concentration of the dissolved solutes or particles in a fluid. Unlike the volume of osmolarity that changes by the addition of more solutes, the volume of osmolality does not change regardless of any factor; as a result, the osmolality of a solution can be easily determined. The unit of osmolality is Osm/Kg, whereas the unit of osmolarity is Osm/L.