Electrolytes

The electrolyte is a substance, solution or melt, which conduct electric current. The electrolytes are related acids, bases and salts. Substances not conduct electric current, dissolved or molten state, is called a non-electrolytes. These include many organic substances, such as sugar, alcohol and other Capacity of electrolyte solutions to conduct the electric current to the fact that the molecules of electrolytes when dissolved break into electrically positively and negatively charged particles (ions. The amount of the charge of an ion is numerically equal to the weight of an atom or group of atoms forming ion. Ions are different from the atoms and molecules not only by the presence of electric charges, but by other properties, for example ions of chlorine have no smell, no color, no other properties of the molecules of chlorine. Positively charged ions are called cations, negatively charged-anions. Cations form atoms of hydrogen H+, metal: K+, Na+, CA2+, Fe3+ and some groups of atoms, for example, the group ammonium NH+4 ; anions form atoms or groups of atoms, which is the acid residues, such as Cl-, NO-3, SO2-4, CO2-3 .
The collapse of the molecules of electrolyte ions is called electrolytic dissociation, or ionization, and is a reversible process, i.e. in the solution to attain a state of equilibrium where many molecules of electrolytes splits into ions, as many of their newly formed of ions. Dissociation of electrolytes on the ions can be represented by the General equation: , where KmAn - medicationabana molecule, z+1 - cation carrying z1 positive charges, Andz-2 - anion with z2 negative charges, m, and n is the number of cations and anions are produced in the dissociation of one molecule of the electrolyte. For example, .
The number of positive and negative ions in the solution may be different, but the total charge cations always equal to the total charge of anions, so the solution in General electrically neutral.
Strong electrolytes almost completely dissociated into ions at any concentration, in their solution. These include a strong acid (see), strong bases and almost all salt (see). A weak electrolyte, which include weak acids and bases, and some salts, such as mercuric chloride HgCl2, dissociate only partially; the degree of dissociation, i.e. the share of molecules, dissolved ions, increases with decreasing the concentration of the solution.
A measure of the ability of electrolytes to disintegrate into ions in solutions can serve as the electrolytic dissociation constant (constant ionization)equal
where in square brackets shows the concentrations of the corresponding particles in the solution.
When passing through the electrolyte solution of the direct electric current cations are moved to a negatively charged electrode - cathode, anions move to the positive electrode (the anode, where cast their charges, becoming electrically neutral atoms or molecules (cations receive electrons from the cathode, and anions give electrons at the anode). As the process of attachment of electrons to the substance is recovering, and the process of recoil electrons substance - oxidation, by passing an electric current through the electrolyte solution at the cathode is the restoration of cations, and at the anode oxidation of anions. This oxidation-reduction process called electrolysis.
Electrolytes are indispensable components of liquids and dense tissue of organisms. In physiological and biochemical processes play an important role such inorganic ions, as N+, Na+, K+, CA2+, Mg2+, HE-C1-HCO-3, H2RO-4, SO2-4 (see Mineral metabolism). Ions H+ and ITis in the human body are in very small concentrations, but their role in the processes of life is overwhelming (see Acid-base balance). The concentration of the ions Na+ and Cl- far exceeds that of all other inorganic ions together. Cm. also, Buffer solutions, Ionites.

The electrolyte is a substance, solution or melt, which conduct electric current. Typical electrolytes are salts, acids and bases.
According to the theory of electrolytic dissociation Arrhenius equation molecules in solutions of electrolytes spontaneously break into the positively and negatively charged particles (ions. Positively charged ions are called cations, negatively charged - anions. The amount of the charge of an ion is determined by the valence (see) atom or group of atoms that constitute this ion. Cations form usually metal atoms, such as+, Na+, Ca2+, Mg3+, Fe3+, and some other groups of atoms (for example, a group of ammonium NH4); anions, as a rule, are formed by atoms and groups of atoms, which is the acid residues, such as Cl-, J-, Br-, S2-, NO3-, CO3, SO4, PO4. Each molecule is electrically neutral, so the number of elementary positive charges cations equal to the number of elementary negative charges of anions are produced in the dissociation of molecules. Presence of ions due to the ability of electrolyte solutions to conduct the electric current. Therefore, the solutions of electrolytes called ionic conductors, or guides of the second kind.
Dissociation of molecules of electrolyte ions can be presented the following General equation:
where KpAq - medicationabana molecule, KP+1 - cation carrying n1 positive charges, AP - anion with n2 negative charges, p and q is the number of cations and anions, are part of the molecule of the electrolyte. For example, the dissociation of sulfuric acid and hydroxide ammonium is expressed by the equations:
The number of ions contained in the solution was measured in grams-ions on 1 l of a solution. Gram-ion - ion mass of this kind, expressed in grams and is numerically equal to the formula weight of the ion. Formula weight find the sum of the atomic weights of atoms forming this ion. For example, a formula weight of ions SO4-equal: 32,06+4-16,00=96,06.
Electrolytes are divided into low molecular weight, macromolecular (polyelectrolytes and colloid. Examples of low-molecular electrolyte, or just electrolytes, may serve as usual low-molecular acids, bases and salts, which are in turn divided into strong and weak electrolytes. Weak electrolytes not completely dissociated into ions, resulting in a solution of it is the dynamic balance between ions and medicationavandiaga molecules electrolytes (equation 1). As weak electrolytes are weak acids, weak bases and some salt, such as mercuric chloride HgCl2. Quantitatively the process of dissociation can be characterized by the degree of electrolytic dissociation degree of ionization) alpha, isotonic factor i and electrolytic dissociation constant (constant ionization) K. the Degree of electrolytic dissociation α call the proportion of molecules of electrolytes, which breaks down into ions in the solution. Value and measured in fractions of a unit or in %, depends on the nature of the electrolyte and solvent: it decreases with increase in concentration of a solution and usually slightly changes (increases or decreases) with increasing temperature; it is also affected by the introduction into the solution of this electrolyte stronger electrolyte, forming the same name of Nona (for example, the degree of electrolytic dissociation of acetic acid CH3COOH decreases adding to its hydrochloric acid HCl or sodium acetate CH3COONa).
Isotonic ratio, or the ratio of van't Hoff, i is equal to the sum of the number of ions and narodoslawsky molecules of the electrolyte to the number of its molecules, taken for preparation of a solution. I is determined experimentally by measuring osmotic pressure, lowering the freezing point of the solution (see Geometria) and some other physical properties of the solutions. The values of i and II related equation
where n is the number of ions produced in the dissociation of one molecule of this electrolyte.


The electrolytic dissociation constant K is a constant of balance. If the electrolyte dissociates ions by the equation (1)then
where, and [KpAq] - concentration in the solution of cations and anions (g-ion/l) and medicationovernight of molecules (mol/l), respectively. Equation (3) is a mathematical expression of the mass action law as applied to the process of electrolytic dissociation. The more It is, the electrolyte better splits into ions. For this electrolyte To depend on temperature (usually with increasing temperature increases) and, unlike a, does not depend on the concentration of the solution.
If the molecule weak electrolyte can dissotsiiruut not on two, but on a larger number of ions, the dissociation occurs in stages (step dissociation). For example, weak carbonic acid H2FROM3 in aqueous solutions dissociates in two stages:
1st level:
2nd level:
While the dissociation constant of the 1st stage is considerably higher than that of the 2nd stage.
Strong electrolytes according to the theory of Debye-chukkala in solutions of fully dissociative ions. Examples of these electrolytes can serve as a strong acids, strong bases and almost all of soluble salts. Because of the almost total dissociation of strong electrolytes in their solutions contains a huge number of ions, the distances between which are such that between the oppositely charged ions are the electrostatic force of attraction, so that each ion is surrounded by ions of opposite charge (ionic atmosphere). The presence of ionic atmosphere reduces chemical and physiological activity of ions, their mobility in the electric field, and other properties of ions. The electrostatic attraction between oppositely charged ions increases with increase in ionic force of a solution equal to the sum of products of concentration With each ion in the square of its valence Z:
(4)
For example, ionic force of 0.01 molar solution MgSO4 equal
Solutions of strong electrolytes regardless of their nature at the same ionic strength (not exceeding, however, 0,1) have the same ionic activity. Ion power of the blood of man is not greater than 0.15. For the quantitative description of properties of solutions of strong electrolytes was introduced value, called the activity and formally replaces the concentration in equations arising from the law of mass action, such as in equation (1). Activity and having the dimension of the concentration associated with the concentration equation
a=f·(5)
where f is the activity factor, showing what proportion of the actual concentration of these ions in the solution is effective concentration or activity. With a decrease in the concentration of the solution f is increasing and in very dilute solutions is equal to 1; in the latter case a=C.
Low-molecular electrolyte are indispensable components of liquids and dense tissue of organisms. From ions of low-molecular electrolyte in physiological and biochemical processes play an important role cations H+, Na+, Mg2+, Ca2+ and anions IT-, Cl-, NSOs3, H2RO4, the MIT4, SO4 (see Mineral metabolism). The ions H + and Oh - organisms, including humans, are in very small concentrations, but their role in the processes of life is overwhelming (see Acid-base balance). Concentrations of Na+ and Cl - far exceed the concentration of all other ions together.
For living organisms highly characteristic of the so-called antagonism ions - the ability of ions in solution, mutually reduce inherent in each of them the action. It is established, for example, that ions of Na+ in the concentration in which they are found in the blood, toxic to many isolated bodies of animals. However, the toxicity of Na+ is adding to the containing solution in the corresponding concentration of ions K+ and Ca2 + . Thus, ions K+ and Ca2+ are antagonists of Na+. Solutions in which harmful effect to any of ions eliminated by the action of the ion antagonists, are called equilibriating solutions. The antagonism of the ions detected by their action on a variety of physiological and biochemical processes.
Polyelectrolytes are called high-molecular electrolyte; examples of these include proteins, nucleic acids, and many other biopolymers (see high-Molecular compounds), and a number of synthetic polymers. As a result of dissociation of polyelectrolytes formed by low-molecular ions (counterions), as a rule, are of different nature and multicharged macromolecular ion. Part of counterions closely associated with macromolecular ion electrostatic forces; the rest are in solution in the free state.
Examples of colloidal electrolytes can serve as soap, tannins and some dyes. For solution of these substances are characterized by equilibrium:
micelles (colloidal particles) - > molecules → ions.
When diluted solution of the equilibrium moves from left to right.
Cm. also Ampholytes.