Osmotic pressure
- 2. OSMOTIC PRESSURE CourseTitle: Physical Chemistry II Course Code: ACCE 260 Applied Chemistry & Chemical Engineering
- 3. SHAIKH ASHRAFUL ALAM Dept. of Applied Chemistry & Chemical Engineering BSMRSTU,Gopalgang,Bangladesh
- 4. Osmosis The 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 Solvent Concentrated Solution semi permeable membrane Solvent molecule Solute molecule
- 5. Osmotic Pressure Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent interior flow of water across a semipermeable membrane. or The pressure required to stop osmosis.
- 6. Osmosis and Osmotic Pressure
- 7. Determination of Osmotic Pressure Pfeffer’s Method Berkely and Harthey’s Method A Modern Osmometer.
- 8. Important term of osmosis & Osmotic pressure Isotonic: 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
- 9. Law of osmotic pressure Boyle-van’t Hoff law for solutions Charles’- Van’t Hoff law for solution Combination of two law we get Van’t Hoff law for solution π𝑉 = 𝑛𝑅𝑇 ( here 𝜋 is osmotic pressure)
- 10. Calculating osmotic pressure The ideal gas law states But n/V = M and so Where 𝑀 is the molar concentration of particles and 𝜋 is the osmotic pressure, 𝑖 isVan’t Hoff factor 𝑃𝑉 = 𝑛𝑅𝑇 𝜋 = 𝑖𝑀𝑅𝑇
- 11. Relation between osmatic pressure and other colligative properties ∆𝑇𝑖 = (𝑅𝑇𝑖)2 ∆𝐻𝑖 × 𝑛2 𝑛1 + 𝑛2 = (𝑅𝑇 𝑖)2 ∆𝐻 𝑖 × 𝑥2 Here, ∆𝑇𝑖 is the elevation in the boiling or depression in the freezing point. 𝑇𝑖 is the boiling or freezing point of the solvent. ∆𝐻𝑖 is the enthalpy change during phase change. 𝑥2 is the mole fraction of solute in solution.
- 12. 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
- 13. Importance of Osmosis and Osmotic Pressure Oncotic pressure of blood plasma Formation of tissue fluid Regulation of cell volume