Osmolarity

Osmolarity is the number of particles per litre of solution. It is a measure of soulte concentration. Osmolarity of a solution is based on the number of ions the molecule dissolved in the solution dissociates into and the molar concentration of that solution. For example, NaCl dissociates into two ions (Na+ and Cl-) within aqueous conditions. Osmolarity = M x n (no.of ions). As a result, in a 1M solution of NaCl, the osmolarity will be 2Osm.

One way in which osmolarity is regulated is by the pumping out of ions by the sodium/potassium pump.