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OSMOTIC PRESSURECourse Title: Physical Chemistry IICourse Code: ACCE 260Applied Chemistry & Chemical Engineering

SHAIKH ASHRAFUL ALAM Dept. of Applied Chemistry & Chemical Engineering BSMRSTU,Gopalgang,Bangladesh

OsmosisThe passage of solvent into solution or from more dilute to concentrated solution when the two are separated from each other by a semipermeable membrane is known as osmosis.Diffusion of water through the semi permeable membrane from a solution of lower concentration towards a solution of higher concentration

Pure SolventConcentrated Solutionsemi permeable membrane Solvent molecule

Solute molecule

A semi-permeable membrane discriminates on the basis of molecular typeSolvent molecules pass throughLarge molecules or ions are blocked

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Osmotic PressureOsmotic pressure is the minimum pressure which needs to be applied to a solution to prevent interior flow of water across a semipermeable membrane. orThe pressure required to stop osmosis.

Osmosis and Osmotic Pressure

Determination of Osmotic PressurePfeffers MethodBerkely and Hartheys MethodA Modern Osmometer.

Important term of osmosis & Osmotic pressureIsotonic: Solutions have equal concentration of solute, and so equal osmotic pressure. Hypertonic: Solution with higher concentration of solute.Hypotonic: Solution with lower concentration of solute.

Isotonic

Hypertonic

Hypotonic

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Law of osmotic pressure

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Calculating osmotic pressure

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Relation between osmatic pressure and other colligative properties

Osmotic Pressure Applications:Osmotic pressure effects normally move solvent molecules from a dilute to a concentrated solution. In water desalination a large external pressure is used to push solvent molecules (water) from sea water through a membrane to produce drinking water. The process is shown below.

Desalination of saltwater by reverse osmosis

Importance of Osmosis and Osmotic PressureOncotic pressure of blood plasmaFormation of tissue fluidRegulation of cell volume

Oncotic or colloid osmotic pressure is a form of osmotic pressure exerted by proteins.13