How does osmotic pressure affect solute concentration?

Osmotic pressure is a result of concentration, not a cause, so the way it affects concentration is by causing osmosis to occur.

Osmotic pressure is a colligative property, which means it is a result of having a mixture of individual particles (solutes) inside a predominantly fluid environment (solvent) (we will ignore solid here, as alloys cannot perform osmosis).

The osmotic pressure is essentially how much water is drawn in through a semipermeable membrane (a membrane that allows the to pass through but not the solutes). We typically only work with water as the solvent so I will stay in that mode from now on.

Refer to this diagram to see how water preferentially passes from the solution with fewer solutes to the solution with more solutes (it’s an average, water molecules are actually passing both ways). You can think of the solution with more solutes as having less water, and the solutes also stick to their water more, preventing water molecules from going back as much.

Eventually the level that is higher has more gravitational pull, so the total difference in fluid height creates a pressure equal and opposite to the osmotic pressure of water preferentially flowing to that side. This has the effect of diluting the more concentrated side and concentrating the more dilute side.

Also note that if the concentrations become equal then the osmosis will be balanced (water flowing through both sides equally). So to answer your question, osmotic pressure will cause the two concentrations to equalize, but only if there is a semipermeable membrane between them.

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