This presentation discusses osmotic pressure and its related concepts. Osmosis is the passage of solvent through a semipermeable membrane from a less concentrated to a more concentrated solution. Osmotic pressure is the minimum pressure required to prevent osmosis, or the flow of water across the membrane. It further defines isotonic, hypertonic, and hypotonic solutions and outlines methods to determine osmotic pressure. Van't Hoff's law relates osmotic pressure to concentration and temperature. Osmotic pressure has important applications including desalination and maintaining fluid balance in the body.

1. Welcome
to
My Presentation

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