What are electrolytes. Cheat sheet "electrolytes and non-electrolytes"

In the section on the question What substances are electrolytes? given by the author Olga Dubrovina the best answer is Substances that decompose into ions in solutions or melts and therefore conduct electric current are called electrolytes. Substances that do not decompose into ions under the same conditions and do not conduct electric current are called non-electrolytes. Strong electrolytes are substances that, when dissolved in water, almost completely decompose into ions. As a rule, strong electrolytes include substances with ionic or highly polar bonds: all highly soluble salts, strong acids (HCl, HBr, HI, HClO4, H2SO4, HNO3) and strong bases (LiOH, NaOH, KOH, RbOH, CsOH, Ba (OH) 2, Sr (OH) 2, Ca (OH) 2). In a strong electrolyte solution, the solute is mainly in the form of ions (cations and anions); non-dissociated molecules are practically absent. Weak electrolytes Substances that partially dissociate into ions. Solutions of weak electrolytes, along with ions, contain undissociated molecules. Weak electrolytes cannot give a high concentration of ions in solution. Weak electrolytes include: 1) almost all organic acids (CH3COOH, C2H5COOH, etc.); 2) some inorganic acids (H2CO3, H2S, etc.); 3) almost all poorly soluble salts, bases and ammonium hydroxide in water (Ca3 (PO4) 2; Cu (OH) 2; Al (OH) 3; NH4OH); 4) water. They poorly (or almost do not conduct) electric current. СH3COOH « CH3COO- + H+Cu(OH)2 « + + OH- (first stage)+ « Cu2+ + OH- (second stage) H2CO3 « H+ + HCO- (first stage) HCO3- « H+ + CO32- (second stage)

Answer from Prosyanka[guru]
acids, bases and some salts

Answer from European[guru]
Yes, acids, salts and alkalis, but in general those who in a dissolved state do not conduct so in their pure form

Answer from Adaptability[guru]
Any that dissociate into ions in water .. :-))

Answer from Anel Saduakasova[newbie]
ELECTROLYTES are solutions of salts, acids and alkalis, as well as molten salts and metals. Electrolytes are good conductors of electric current.

Answer from Olia Titova[newbie]
all highly soluble salts, strong acids (HCl, HBr, HI, HClO4, H2SO4, HNO3) and strong bases (LiOH, NaOH, KOH, RbOH, CsOH, Ba(OH)2,Sr(OH)2,Ca(OH) 2).

Answer from Yohlana[master]
Electrolytes include: acids, salts, alkalis

Answer from Ling Kwon[newbie]
With ionic and covalent polar type of chemical bond.

- (Greek). A liquid body decomposed by an electric (galvanic) current. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. ELECTROLYTE A liquid subject to decomposition by galvanic current. ... ... Dictionary of foreign words of the Russian language

electrolyte- a, m. electrolyte m. electro + gr. lytos is degradable. specialist. A chemical substance (in melt or solution) that can be decomposed into its component parts when an electric current is passed through it. battery electrolyte. BASS 1. Throwing ... ... Historical Dictionary of Gallicisms of the Russian Language

electrolyte- A solution in which, when an electric current passes through it, the decomposition of a substance occurs, which leads to the appearance of an electric current. The electrolyte is the basis of accumulators and batteries. [Hypertext encyclopedic dictionary on ... ... Technical Translator's Handbook

ELECTROLYTE- ELECTROLYTE, a solution or molten salt capable of conducting electricity and used for ELECTROLYSIS (during which it decomposes). Current in electrolytes is conducted by charged particles IONS, not electrons. For example, in lead ... ... Scientific and technical encyclopedic dictionary

ELECTROLYTE- ELECTROLYTE, electrolyte, husband. (from the word electric and Greek lytos dissolved) (physical). A solution of a substance capable of being broken down into its component parts by electrolysis. Explanatory Dictionary of Ushakov. D.N. Ushakov. 1935 1940 ... Explanatory Dictionary of Ushakov

electrolyte- noun, number of synonyms: 1 catholyte (1) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

Electrolyte- Electrolytes are substances, solutions and alloys of which, with other substances, electrolytically conduct galvanic current. A sign of electrolytic conductivity, in contrast to metallic, should be considered the ability to observe chemical ... ... Encyclopedia of Brockhaus and Efron

electrolyte- - a substance whose aqueous solution or melt conducts an electric current. General chemistry: textbook / A. V. Zholnin ... Chemical terms

ELECTROLYTE- a substance whose aqueous solution or melt conducts an electric current (see), resulting from electrolytic (see). This E., also called (see) the second kind, differ from metals (conductors of the first kind), in which the transfer ... Great Polytechnic Encyclopedia

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Inorganic Chemistry Part I Surface Phenomena at the Oxide-Electrolyte Boundary in Acid Media Tutorial ,

Electrolytes are substances whose solutions or melts conduct electricity. Electrolytes include acids, bases and salts. Substances that do not conduct electric current in a dissolved or molten state are called non-electrolytes. These include many organic substances, such as sugars, etc. The ability of electrolyte solutions to conduct electric current is explained by the fact that electrolyte molecules, when dissolved, decompose into electrically positively and negatively charged particles - ions. The value of the charge of an ion is numerically equal to the valency of the atom or group of atoms that form the ion. Ions differ from atoms and molecules not only in the presence of electric charges, but also in other properties, for example, ions have neither smell, nor color, nor other properties of chlorine molecules. Positively charged ions are called cations, negatively charged anions. Cations form hydrogen H + , metals: K + , Na + , Ca 2+ , Fe 3+ and some groups of atoms, for example, the ammonium group NH + 4; anions form atoms and groups of atoms that are acid residues, for example Cl - , NO - 3 , SO 2- 4 , CO 2- 3 .

The breakdown of electrolyte molecules into ions is called electrolytic dissociation, or ionization, and is a reversible process, that is, an equilibrium state can occur in a solution in which how many electrolyte molecules decompose into ions, so many of them are re-formed from ions. The dissociation of electrolytes into ions can be represented by the general equation: where KmAn is an undissociated molecule, K z + 1 is a cation carrying z 1 positive charges, A z- 2 is an anion having z 2 negative charges, m and n are the number of cations and anions formed during the dissociation of one electrolyte molecule. For example, .

The number of positive and negative ions in a solution can be different, but the total charge of the cations is always equal to the total charge of the anions, so the solution as a whole is electrically neutral.

Strong electrolytes almost completely dissociate into ions at any concentration in solution. These include strong acids (see), strong bases and almost all salts (see). Weak electrolytes, which include weak acids and bases and some salts, such as mercuric chloride HgCl 2 , dissociate only partially; the degree of their dissociation, i.e., the proportion of molecules decomposed into ions, increases with decreasing solution concentration.

A measure of the ability of electrolytes to decompose into ions in solutions can be the electrolytic dissociation constant (ionization constant), equal to
where square brackets show the concentrations of the corresponding particles in the solution.

When a constant electric current is passed through the electrolyte solution, the cations move to the negatively charged electrode - the cathode, the anions move to the positive electrode - the anode, where they give up their charges, turning into electrically neutral atoms or molecules (cations receive electrons from the cathode, and anions donate electrons at the anode) . Since the process of attaching electrons to a substance is reduction, and the process of donating electrons by a substance is oxidation, when an electric current is passed through an electrolyte solution, cations are reduced at the cathode, and anions are oxidized at the anode. This redox process is called electrolysis.

Electrolytes are an indispensable component of liquids and dense tissues of organisms. In physiological and biochemical processes, such inorganic ions as H +, Na +, K +, Ca 2+, Mg 2+, OH -, Cl -, HCO - 3, H 2 PO - 4, SO 2- 4 (see Mineral exchange). Ions H + and OH - in the human body are in very low concentrations, but their role in life processes is enormous (see Acid-base balance). The concentration of Na + and Cl - ions significantly exceeds that of all other inorganic ions combined. See also Buffer solutions, Ion exchangers.

Electrolytes are substances whose solutions or melts conduct electric current. Typical electrolytes are salts, acids and bases.

According to the Arrhenius theory of electrolytic dissociation, electrolyte molecules in solutions spontaneously decompose into positively and negatively charged particles - ions. Positively charged ions are called cations, negatively charged anions. The value of the charge of an ion is determined by the valency (see) of the atom or group of atoms that form this ion. Cations usually form metal atoms, for example, K+, Na+, Ca2+, Mg3+, Fe3+, and some groups of other atoms (for example, the ammonium group NH 4); anions, as a rule, are formed by atoms and groups of atoms that are acidic residues, for example Cl-, J-, Br-, S2-, NO 3 -, CO 3 , SO 4 , PO 4 . Each molecule is electrically neutral, so the number of elementary positive charges of cations is equal to the number of elementary negative charges of anions formed during the dissociation of the molecule. The presence of ions explains the ability of electrolyte solutions to conduct electric current. Therefore, electrolyte solutions are called ionic conductors, or conductors of the second kind.

The dissociation of electrolyte molecules into ions can be represented by the following general equation:

where is an undissociated molecule, is a cation with n1 positive charges, is an anion with n2 negative charges, p and q are the number of cations and anions that make up the electrolyte molecule. So, for example, the dissociation of sulfuric acid and ammonium hydroxide is expressed by the equations:

The number of ions contained in a solution is usually measured in gram ions per 1 liter of solution. Gram-ion - the mass of ions of a given type, expressed in grams and numerically equal to the formula weight of the ion. The formula weight is found by summing the atomic weights of the atoms that form a given ion. So, for example, the formula weight of SO 4 ions is equal to: 32.06+4-16.00=96.06.

Electrolytes are divided into low molecular weight, high molecular weight (polyelectrolytes) and colloidal. Examples of low molecular weight electrolytes, or simply electrolytes, are ordinary low molecular weight acids, bases and salts, which in turn are usually divided into weak and strong electrolytes. Weak electrolytes do not completely dissociate into ions, as a result of which a dynamic equilibrium is established in the solution between ions and undissociated electrolyte molecules (equation 1). Weak electrolytes include weak acids, weak bases, and some salts, such as mercuric chloride HgCl 2 . Quantitatively, the dissociation process can be characterized by the degree of electrolytic dissociation (ionization degree) α, the isotonic coefficient i and the electrolytic dissociation constant (ionization constant) K. The degree of electrolytic dissociation α is the fraction of electrolyte molecules that decomposes into ions in a given solution. The value of a, measured in fractions of a unit or in%, depends on the nature of the electrolyte and solvent: it decreases with increasing solution concentration and usually changes slightly (increases or decreases) with increasing temperature; it also decreases when a stronger electrolyte is introduced into the solution of a given electrolyte, forming the same nones (for example, the degree of electrolytic dissociation of acetic acid CH 3 COOH decreases when hydrochloric acid HCl or sodium acetate CH 3 COONa is added to its solution).

The isotonic coefficient, or van't Hoff coefficient, i is equal to the ratio of the sum of the number of ions and undissociated electrolyte molecules to the number of its molecules taken to prepare the solution. Experimentally, i is determined by measuring the osmotic pressure, lowering the freezing point of a solution (see Cryometry), and some other physical properties of solutions. The values i and α are interconnected by the equation

where n is the number of ions formed during the dissociation of one molecule of a given electrolyte.

The electrolytic dissociation constant K is the equilibrium constant. If the electrolyte dissociates into ions according to equation (1), then

where, and - concentrations in solution of cations and anions (in g-ion/l) and undissociated molecules (in mol/l), respectively. Equation (3) is a mathematical expression of the law of mass action as applied to the process of electrolytic dissociation. The more K, the better the electrolyte decomposes into ions. For a given electrolyte, K depends on temperature (usually it increases with increasing temperature) and, unlike a, does not depend on the concentration of the solution.

If a weak electrolyte molecule can dissociate not into two, but into a greater number of ions, then the dissociation proceeds in stages (stepwise dissociation). For example, weak carbonic acid H 2 CO 3 in aqueous solutions dissociates in two steps:

In this case, the dissociation constant of the 1st stage significantly exceeds that of the 2nd stage.

Strong electrolytes, according to the Debye-Hückel theory, in solutions are completely dissociated into ions. Examples of these electrolytes are strong acids, strong bases, and almost all water-soluble salts. Due to the complete dissociation of strong electrolytes, their solutions contain a huge number of ions, the distances between which are such that electrostatic attraction forces appear between oppositely charged ions, due to which each ion is surrounded by ions of the opposite charge (ionic atmosphere). The presence of an ionic atmosphere reduces the chemical and physiological activity of ions, their mobility in an electric field, and other properties of ions. The electrostatic attraction between oppositely charged ions increases with an increase in the ionic strength of the solution, which is equal to half the sum of the products of the concentration C of each ion and the square of its valency Z:

So, for example, the ionic strength of a 0.01 molar solution of MgSO 4 is

Solutions of strong electrolytes, regardless of their nature, with the same ionic strength (however, not exceeding 0.1) have the same ionic activity. The ionic strength of human blood does not exceed 0.15. For a quantitative description of the properties of solutions of strong electrolytes, a quantity called activity a was introduced, which formally replaces the concentration in equations arising from the law of mass action, for example, in equation (1). Activity a, which has the dimension of concentration, is related to concentration by the equation

where f is the activity coefficient, showing what proportion of the actual concentration of these ions in the solution is their effective concentration or activity. As the concentration of the solution decreases, f increases and in very dilute solutions becomes equal to 1; in the latter case, a = C.

Low molecular weight electrolytes are an indispensable component of liquids and dense tissues of organisms. Of the ions of low molecular weight electrolytes, H+, Na+, Mg2+, Ca2+ cations and anions OH-, Cl-, HCO 3 , H 2 PO 4 , HPO 4 , SO 4 play an important role in physiological and biochemical processes (see Mineral metabolism). Ions H + and OH- in organisms, including the human body, are in very low concentrations, but their role in life processes is enormous (see Acid-base balance). The concentrations of Na+ and Cl- greatly exceed the concentration of all other ions combined.

For living organisms, the so-called antagonism of ions is highly characteristic - the ability of ions in solution to mutually reduce the action inherent in each of them. It has been established, for example, that Na + ions in the concentration in which they are found in the blood are poisonous for many isolated organs of animals. However, the toxicity of Na+ is suppressed when K+ and Ca2+ ions are added to the solution containing them in appropriate concentrations. Thus, K+ and Ca2+ ions are antagonists of Na+ ions. Solutions in which the harmful effect of any ions is eliminated by the action of antagonist ions are called equilibrated solutions. Antagonism of ions was discovered when they act on a variety of physiological and biochemical processes.

Polyelectrolytes are called high-molecular electrolytes; examples are proteins, nucleic acids, and many other biopolymers (see Macromolecular Compounds), as well as a number of synthetic polymers. As a result of the dissociation of macromolecules of polyelectrolytes, low molecular weight ions (counterions) are formed, as a rule, of a different nature and a multiply charged macromolecular ion. Some of the counterions are firmly bound to the macromolecular ion by electrostatic forces; the rest are in solution in a free state.

Soaps, tannins, and certain dyes are examples of colloidal electrolytes. Solutions of these substances are characterized by equilibrium:
micelles (colloidal particles) → molecules → ions.

When the solution is diluted, the equilibrium shifts from left to right.

Dissociation of electrolytes

Electrolytes are substances with ionic or highly polar covalent bonds. The former exist in the form of ions even before they are transferred to a dissolved or molten state. Electrolytes include salts, bases, acids.

Rice. 1. Table difference between electrolytes and non-electrolytes.

Distinguish between strong and weak electrolytes. Strong electrolytes, when dissolved in water, completely dissociate into ions. These include: almost all soluble salts, many inorganic acids (for example, H 2 SO 4 , HNO 3 , HCl), hydroxides of alkali and alkaline earth metals. Weak electrolytes, when dissolved in water, slightly dissociate into ions. These include almost all organic acids, some inorganic acids (for example, H 2 CO 3), many hydroxides (except hydroxides of alkali and alkaline earth metals).

Rice. 2. Table of strong and weak electrolytes.

Water is also a weak electrolyte.

Like other chemical reactions, electrolytic dissociation in solutions is written as dissociation equations. At the same time, for strong electrolytes, the process is considered as going irreversibly, and for electrolytes of medium strength and weak ones, as a reversible process.

acids- These are electrolytes, the dissociation of which in aqueous solutions proceeds with the formation of hydrogen ions as cations. Polybasic acids dissociate in steps. Each next step goes with more and more difficulty, since the resulting ions of acid residues are weaker electrolytes.

Foundations- electrolytes that dissociate in an aqueous solution with the formation of a hydroxide ion OH- as an anion. The formation of a hydroxide ion is a common feature of bases and determines the general properties of strong bases: alkaline character, bitter taste, soapiness to the touch, reaction to an indicator, neutralization of acids, etc.

Alkalis, even slightly soluble ones (for example, barium hydroxide Ba (OH) 2) dissociate completely, for example:

Ba (OH) 2 \u003d Ba 2 + 2OH-

salt- these are electrolytes that dissociate in an aqueous solution with the formation of a metal cation and an acid residue. Salts do not dissociate in steps, but completely:

Ca (NO 3) 2 \u003d Ca 2 + + 2NO 3 -

Theory of electrolytic dissociation

electrolytes- substances that undergo electrolytic dissociation in solutions or melts and conduct electric current due to the movement of ions.

Electrolytic dissociation is the breakdown of electrolytes into ions when they are dissolved in water.

The theory of electrolytic dissociation (S. Arrhenius, 1887) in the modern sense includes the following provisions:

Electrolytes, when dissolved in water, decompose (dissociate) into ions - positive (cations) and negative (anions). Ionization occurs most easily for compounds with an ionic bond (salts, alkalis), which, when dissolved (an endothermic process of destruction of the crystal lattice), form hydrated ions.

Rice. 3. Scheme of electrolytic dissociation of salt.

Hydration of ions is an exothermic process. The ratio of energy costs and gains determines the possibility of ionization in solution. When a substance with a polar covalent bond (for example, hydrogen chloride HCl) is dissolved, water dipoles orient themselves at the corresponding poles of the dissolved molecule, polarize the bond and turn it into an ionic one, followed by hydration of the ions. This process is reversible and can go either completely or partially.

hydrated ions are stable and move randomly in solution. Under the action of an electric current, the motion acquires a directed character: cations move towards the negative belt (cathode), and anions - towards the positive belt (anode).
dissociation (ionization) is a reversible process. The completeness of ionization depends on the nature of the electrolyte (alkali salts dissociate almost completely), its concentration (ionization becomes more difficult with an increase in concentration), temperature (an increase in temperature promotes dissociation), the nature of the solvent (ionization occurs only in a polar solvent, in particular, in water).

These are substances whose solutions or melts conduct an electric current. They are also an indispensable component of liquids and dense tissues of organisms.

Electrolytes include acids, bases and salts. Substances that do not conduct electric current in a dissolved or molten state are called non-electrolytes. These include many organic substances, such as sugars, alcohols, etc. The ability of electrolyte solutions to conduct electric current is explained by the fact that electrolyte molecules, when dissolved, decompose into electrically positively and negatively charged particles - ions. The value of the charge of an ion is numerically equal to the valency of the atom or group of atoms that form the ion. Ions differ from atoms and molecules not only in the presence of electric charges, but also in other properties, for example, chlorine ions have neither smell, nor color, nor other properties of chlorine molecules.

Positively charged ions are called cations, negatively charged anions. Cations form hydrogen atoms H + , metals: K + , Na + , Ca 2+ , Fe 3+ and some groups of atoms, for example, the ammonium group NH + 4; anions form atoms and groups of atoms that are acid residues, for example Cl - , NO - 3 , SO 2- 4 , CO 2- 3 .

The term E. was introduced into science by Faraday. Until very recently, typical salts, acids and alkalis, as well as water were attributed to K. E. Studies of non-aqueous solutions, as well as studies at very high temperatures, have greatly expanded this area. I. A. Kablukov, Kadi, Karara, P. I. Walden and others showed that not only aqueous and alcoholic solutions conduct electricity noticeably, but also solutions in a number of other substances, such as, for example, in liquid ammonia, liquid sulfur dioxide anhydride; The famous Nernst incandescent lamp, the principle of which was discovered by the brilliant Yablochkov, is an excellent illustration of these facts. A mixture of oxides - the "incandescent body" in a Nernst lamp, which is not conductive at ordinary temperature, at 700 ° becomes excellent and, moreover, retains a solid state electrolytic conductor. It can be assumed that most of the complex substances studied in inorganic chemistry, with appropriate solvents or at a sufficiently high temperature, can acquire the properties of electrons, with the exception, of course, of metals and their alloys and those complex substances for which metallic conductivity will be proved. At the moment, the indications of the metallic conductivity of molten silver iodide, etc., must be considered insufficiently substantiated. The other must be said about the majority of substances containing carbon, that is, those studied in organic chemistry. It is unlikely that there will be solvents that will make hydrocarbons or their mixtures (paraffin, kerosene, gasoline, etc.) current conductors. However, in organic chemistry we also have a gradual transition from typical electrolytes to typical non-electrolytes: starting from organic acids, to phenols containing a nitro group in their composition, to phenols that do not contain such a group, to alcohols, aqueous solutions of which belong to insulators with small electrical excitation forces and , finally, to hydrocarbons - typical insulators. For many organic, and also to some extent also some inorganic compounds, it is difficult to expect that an increase in temperature will make them e., since these substances decompose earlier from the action of heat.

In such an indefinite state was the question of what E. is, until his theory of electrolytic dissociation was brought to the decision.

electrolytic dissociation.

The dissociation of electrolytes into ions can be represented by the general equation: where KmAn is an undissociated molecule, K z + 1 is a cation carrying z 1 positive charges, A z- 2 is an anion having z 2 negative charges, m and n are the number of cations and anions formed during the dissociation of one electrolyte molecule. For example, .
The number of positive and negative ions in a solution can be different, but the total charge of the cations is always equal to the total charge of the anions, so the solution as a whole is electrically neutral.
Strong electrolytes almost completely dissociate into ions at any concentration in solution. These include strong acids (see), strong bases and almost all salts (see). Weak electrolytes, which include weak acids and bases and some salts, such as mercuric chloride HgCl 2 , dissociate only partially; the degree of their dissociation, i.e., the proportion of molecules decomposed into ions, increases with decreasing solution concentration.
A measure of the ability of electrolytes to decompose into ions in solutions can be the electrolytic dissociation constant (ionization constant), equal to
where square brackets show the concentrations of the corresponding particles in the solution.

Books

Dissociation of electrolytes

Theory of electrolytic dissociation

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