What are the columbative properties of solutions?

Solutions are homogeneous systems that contain two or more components, as well as products that are the result of the interaction of these components. They can be in a solid, liquid or gaseous state. Let us consider the liquid state of the solutions. Their composition includes a solvent and a substance dissolved in it (the latter is less).

The colligative properties of solutions are their characteristics, which are directly dependent only on the solvent and the concentration of the solution. They are also called collective or common. The colligative properties of solutions are manifested in mixtures in which there is no chemical interaction between the constituent components. In addition, the forces of mutual action between the particles of the solvent and the particles of the solvent and the substance dissolved in it are equal in ideal solutions.

Colligative properties of solutions:

1) The vapor pressure is lower over the solution than over the solvent.

2) Crystallization of the solution proceeds at a temperature below the crystallization temperature of the solvent in its pure form.

3) The solution boils at a higher temperature than the boiling of the solvent itself.

4) The phenomenon of osmosis.

Consider the colligative properties separately.

Equilibrium at the boundary of the phases in a closed system: liquid-vapor is characterized by saturated vapor pressure. Since in the solution part of the surface layer is filled with molecules of the solute, equilibrium will be achieved with a lower vapor pressure.

The second colligative property-the decrease in the crystallization temperature of the solution as compared with the solvent-is due to the fact that the particles of the solute interfere in the construction of the crystals, and thereby prevent crystallization with a decrease in temperature.

The boiling point of the mixture is higher than that of the pure solvent, because the equality of atmospheric pressure and saturated vapor pressure is achieved with higher heating, since some of the solvent molecules are bound to the particles of the dissolved substance.

The fourth collusive property of solutions is the phenomenon of osmosis.

The phenomenon of osmosis is the ability of the solvent to migrate through a septum that is permeable to some particles (solvent molecules) and impenetrable to others (molecules of the dissolved substance). This septum separates the solution with a high content of solute from a less concentrated solution. An example of such a semipermeable partition can serve as a membrane of a living cell, a bovine bubble, etc. The phenomenon of osmosis is caused by equalization of concentrations on both sides, separated by a membrane, which is thermodynamically more beneficial for the system. As a result of the displacement of the solvent into a more concentrated solution, an increase in pressure is observed in this part of the vessel. This overpressure was called osmotic.

Mathematically, the colligative properties of solutions of nonelectrolytes can be represented by the equations:

Δ Tkip = Sketch ∙ Sm;

Δ Tcr. = Kzam ∙ Sm;

Π = CRT.

The colligative properties in numerical terms differ for solutions of electrolytes and solutions of nonelectrolytes. For the first, they are somewhat larger. This is due to the fact that electrolytic dissociation occurs in them , and the number of particles increases significantly.

The colligative properties of solutions are widely used in everyday life and in industry, for example, the phenomenon of osmosis is used to produce pure water. In living organisms many systems are also built on the colligative properties of solutions (for example, plant cell growth).