Isotonic coefficient

Isotonic solutions are a special group of solutions that are characterized by osmotic pressure. It has such a value, which is characterized by fluids in the body, such as: blood plasma, tears, lymph and so on. All these liquids have a constant pressure in the region of 7.4 atm. In this case, if an injection is injected into the body, the osmotic pressure of the liquids will be disturbed, since a similar equilibrium will be disturbed.

In order to prepare such a solution, it is necessary to make some calculations. The most well-known method of conducting them is none other than the isotonic coefficient of Van't Hoff. With its help it is possible to calculate the isotonic concentration of a solution of a dilute substance, which is not an electrolyte. The osmotic pressure, the amount of solution, and also its temperature are in a certain relationship, which is expressed by the Clapeyron equation. It is used for dilute solutions, because according to Van Hoff's law, substances dissolved in a liquid will behave in the same way as gases, and therefore all the so-called gas laws apply to them.

The isotonic coefficient is nothing more than a parameter that will characterize the behavior of a substance in a solution. If we talk about the numerical equivalent, the isotonic coefficient is equal to the ratio of the numerical value of the col- ligative property that the solution possesses to the same property of the nonelectrolyte, of the same concentration, while all other parameters remain unchanged.

The physical meaning of the isotonic coefficient becomes clear, based on the definition of each col- ligative parameter. They all depend on the concentration of the substance in the solution of the particles. Electrolytes will not enter dissociation reactions, so each individual molecule of such a substance will be a single particle. Electrolytes in the process of solvation will either completely or partially break down into ions, while forming several particles. It turns out that the colligative properties of the solution will depend on the amount of particles of different types, that is, ions, contained in it. Thus, the isotonic coefficient will be a mixture of different solutions of each type of particles. If you consider a solution of bleach, you can see that it consists of three kinds of particles: calcium cations , hypochlorite, and also chloride anions. The isotonic coefficient will show that there are more particles in the electrolyte solution than in the non-electrolyte solution. The coefficient will depend directly on whether a substance can decay into ions-this is nothing more than a property of dissociation.

Since strong electrolytes are completely exposed to dissociation processes, it is fully justifiable to expect that the isotonic coefficient in this case will be equal to the number of ions contained in the molecule. However, in reality, the value of the coefficient will always be less than the value calculated by the formula. This position was justified in 1923 by Debye and Hückel. They formulated the theory of strong electrolytes: ions will not be obstructed to move, as the shell of solvation will form. Moreover, they will also interact with each other, which leads, in the end, to the formation of such a group that will move in the same direction in the solution. These are the so-called ionic associations, as well as ion pairs. All processes in solution will occur in this way, as if it contains few particles.

The interaction of ions will begin to weaken as the temperature increases, and their concentration also decreases. All this is explained by the fact that in this case the probability of meeting different particles in solution decreases.