what is osmotic pressure

Osmotic pressure is the minimum pressure that needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. It is a colligative property of solutions that is dependent on the concentration of solute particles in the solution/13%3A_Solutions_and_their_Physical_Properties/13.07%3A_Osmotic_Pressure). Osmotic pressure is the pressure caused by a difference in the amounts of solutes between solutions separated by a semipermeable membrane. The net flow of solvent through a semipermeable membrane is called osmosis, and the direction of net solvent flow is always from the side with the lower concentration of solute to the side with the higher concentration/13%3A_Solutions_and_their_Physical_Properties/13.07%3A_Osmotic_Pressure). The osmotic pressure of a solution depends on the concentration of dissolved solute particles and can be calculated using the van t Hoff equation: π = iCRT, where π is osmotic pressure, i is the dimensionless van t Hoff index, c is the molar concentration of solute, R is the ideal gas constant, and T is the absolute temperature/13%3A_Solutions_and_their_Physical_Properties/13.07%3A_Osmotic_Pressure). Osmotic pressure is essential for many living things, including plants, where it is vital in plant turgidity and osmoregulation. In addition, osmotic pressure is the basis of filtering, a process commonly used in water purification.