Osmotic Pressure Equation - Overview, Structure, Properties & Uses

Osmotic Pressure Equation - Overview, Structure, Properties & Uses

What is osmotic pressure?

Osmotic pressure definition: The osmotic pressure of a solution is measured using a semipermeable membrane, a barrier having pores tiny enough to enable solvent molecules to flow through but not solute molecules or ions. Osmosis (from the Greek osmós, meaning "push") is the net flow of a solvent through a semipermeable membrane. Osmotic pressure meaning: The lowest pressure that must be given to a solution to stop the flow of solvent molecules across a semipermeable membrane is known as osmotic pressure (osmosis). It is a colligative feature that is influenced by the solute particle concentration in the solution. The concentration of dissolved solute particles determines the osmotic pressure of a solution. The law of osmotic pressure equation is like the ideal gas equation:

Also read -

  • NCERT Solutions for Class 11 Chemistry

  • NCERT Solutions for Class 12 Chemistry

  • NCERT Solutions for All Subjects

Osmotic pressure formula/Osmotic pressure equation:


Where is the osmotic pressure

The molarity of a solution is defined as the letter M gives the number of moles of solute per unit volume of solution

R is the ideal gas constant,

T is the absolute temperature.

Osmotic pressure units is mol/L.

Jacobus van't Hoff, a Dutch chemist, proposed a link between a solution's colloid osmotic pressure equation and the molar concentration of its solute. It's worth noting that this equation only applies to solutions that behave like perfect ones.

π =iCRT

where π is defined as the osmotic pressure.

i is called the van’t Hoff factor.

C is defined as the molar concentration of the solute present in the solution.

R is called the universal gas constant.

T is the temperature of the system enclosed within.

Osmosis :

What is Osmosis ?

The transport of solvent molecules through a semipermeable membrane from an area with low solute concentration to a region with high solute concentration is referred to as osmosis. The two sides of the semipermeable membrane eventually reach a state of balance (equal solute concentration on both sides of the semipermeable membrane). Solute particles cannot flow through the semipermeable barrier since it only permits solvent molecules to pass through. The osmosis process can be stopped if enough pressure is applied to the solution side of the semipermeable membrane. The osmotic pressure is the minimal amount of pressure required to stop the osmosis process.

Osmosis can be illustrated with the help of a U shaped tube, such as the one shown in figure, which has pure water in one arm and a dilute aqueous solution of glucose in the other. Water flows across the membrane in a net flow until the levels in the arms stop changing, indicating that equilibrium has been reached. The difference in pressure between the two sides, in this case the heights of the two columns, is the osmotic pressure equation (π) of the glucose solution. Although the semipermeable membrane allows water molecules to flow in either way, the rate of flow is different in both directions due to the different concentrations of water in the two arms. By applying a pressure to the right arm equivalent to the osmotic pressure equation of the glucose solution, the net flow of water across the membrane can be blocked.

Reverse Osmosis :

Osmosis in reverse is referred to as reverse osmosis. Whereas osmosis happens naturally without the need of energy, reversing the process requires the application of energy to the more saline solution. The majority of dissolved salts, organics, bacteria, and pyrogens flow through a reverse osmosis membrane, but not the majority of dissolved salts, organics, bacteria, and pyrogens. However, in order to desalinate (demineralize or deionize) water, you must apply pressure to the reverse osmosis membrane that is larger than the naturally occurring osmotic pressure. This allows pure water to pass through while keeping the bulk of impurities out.

Applications and Examples of Osmosis

Plants rely on osmotic pressure to keep their upright structure. When the plant receives enough water, its cells (which contain multiple salts) absorb the water and expand. Plant cells expand, increasing the pressure on their cell walls and forcing them to stand erect. When a plant receives insufficient water, its cells become hypertonic (they shrink due to loss of water). They wilt and lose their solid, erect posture as a result. The molecular weights of substances can also be determined by measuring osmotic pressure. Desalination and purification of saltwater, which includes the use of osmotic pressure, is another key application. Osmosis is extremely significant in biochemistry, biology, and medicine due to the high magnitude of osmotic pressures. Almost every barrier that divides an organism or cell from its environment functions as a semipermeable membrane, allowing water but not solutes to pass through. The compartments within an organism or cell are the same way. Certain specialised barriers, including in your kidneys, are slightly more permeable and use a similar mechanism known as dialysis, which allows water and tiny molecules to pass through but not large molecules like proteins.

Over the long winter, the same method has been employed to preserve fruits and their critical vitamins. Sugar is used in jams and jellies in high proportions not only for sweetness, but also to raise the osmotic pressure. As a result, any bacteria that survive the cooking process are dried, preventing them from growing in an otherwise rich bacterial growth medium. Bacteria cannot develop in ham, bacon, salt pig, salt fish, and other preserved meats thanks to a similar salt-based method. When red blood cells are placed in a solution with an osmotic pressure that is substantially lower or much greater than the internal pressure of the cells, the influence of osmotic pressure is strikingly demonstrated. Osmotic pressure is used by trees to carry water and other nutrients from the roots to the top branches, in addition to capillary action. Water evaporation from the leaves causes a local increase in salt concentration, which causes an osmotic pressure to move water up the tree trunk to the leaves.

Also check-

  • NCERT Exemplar Class 11th Chemistry Solutions

  • NCERT Exemplar Class 12th Chemistry Solutions

  • NCERT Exemplar Solutions for All Subjects