Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute.
Osmotic potential is the opposite of water potential with the former meaning the degree to which a solvent (usually water) would want to stay in a liquid.
When a biological cell is in a hypotonic environment (the cell interior contains a lower concentration of water and a higher concentration of other molecules than its exterior), water flows across the cell membrane into the cell, causing it to expand due tosmotic pressure. In plant cells, the cell wall restricts the expansion, resulting in pressure on the cell wall from within calledturgor pressire. The osmotic pressure π of a dilute solution can be calculated using the formula
π = iMRT,
i is the van 't Hoff factor
M is the molarity
R is the gas constant, where R = 0.08206 L · atm · mol-1 · K-1
T is the thermodynamic temperature (formerly called absolute temperature)
Note the similarity of the above formula to the ideal gas law and also that osmotic pressure is not dependent on particle charge.
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