What is osmotic pressure, and what is it dependent on?
1 Answer
Jul 4, 2017
Osmotic pressure is the pressure that needs to be applied to one side of a semi-permeable membrane to prevent solvent flow across the membrane into the more concentrated side, and is given by:
#Pi = iMRT# ,where:
#i# is the van't Hoff factor for the solute(s), i.e. the effective number of particles in solution per formula unit.#M# is the solution concentration in... well,#"mol/L"# , molarity,#"M"# .#Pi# is the osmotic pressure in#"atm"# , if#R# is the universal gas constant in#"L"cdot"mol/atm"cdot "K"# .#T# is temperature in#"K"# , as usual.
Thus, osmotic pressure is dependent on
- the electrolytic features of the solute (the stronger the electrolyte, the more particles per formula unit, and thus the higher the
#Pi# needed to stop a larger number of solute particles from sucking up the solvent) - the concentration of the solution on one side of the membrane (the higher it is, the greater the
#Pi# needed to stop a higher concentration of solute from sucking up the solvent) - the temperature of the solution (the higher it is, the greater
#Pi# is to stop the faster solvent flow in warmer environments)
These are all direct proportionalities, i.e. as