Osmosis, Reverse Osmosis & Solution Types

Osmosis: Spontaneous flow of solvent molecules from a region of lower solute concentration (dilute) to a higher solute concentration through a semipermeable membrane (SPM).

Reverse Osmosis (RO): Flow of solvent in the reverse direction (from solution to pure solvent) when a pressure greater than the osmotic pressure ($\text{Pressure} > \pi$) is applied on the solution side. Used in desalination of seawater.

Types of Solutions (Based on Osmotic Pressure):

• Isotonic Solutions: Two solutions having equal osmotic pressure ($$\pi_1 = \pi_2$$) at the same temperature. No net osmosis occurs.
• Hypertonic Solution: Solution with a higher osmotic pressure relative to another. RBCs shrink (plasmolysis) when placed in a hypertonic solution.
• Hypotonic Solution: Solution with a lower osmotic pressure relative to another. RBCs swell and burst (hemolysis) when placed in a hypotonic solution.