Organic compounds containing oxygen Monocarboxylic acids.

C₁-HCOOH-Methanoic acid-Formic acid (Common name) -(formiate); C₂-CH₃COOH-Ethanoic acid-Acetic acid-(acetate); C₃-CH₃CH₂COOH-Propanoic acid-Propionic acid-(propionate; C₄-CH₃(CH₂)₂COOH-Butanoic acid-Butyric acid- (butyrate) C₅-CH₃(CH₂)₃COO-Pentanoic acid-Valeric acid-(valerate); C₆-CH₃(CH₂)₄COOH-Hexanoic acid-Caproic acid-(caproate) ДИКАРБОНОВЫЕ C₂-HOOC-COOH-Ethanedioic acid-Oxalic acid-Oxalate C₃-HOOC-CH₂-COOH-Propanedioic acid-Malonic acid-Malonate; C₄-HOOC-(CH₂)₂-COO-Butanedioic acid-Succinic acid-Succinate; C₅-HOOC-(CH₂)₃-COOH-Pentanedioic acid-Glutaric acid-Glutarate. ESTERS This name is given to those generally smelling substances that contain the esters functional group R-COO-R₁. The sweet and pleasant odours and tastes of many foods are due to complex mixtures of organic compounds, of which esters are generally the most prevalent component. Table lists some of the esters that are used as flavouring agents.Пример methyl butanoate, ethyl butanoate, butyl butanoate. ETHERS These are substances that contain two organic groups attached to the same OXYGEN atom. i.e. They contain the functional group - R – O – R’ The R groups may be aromatic or aliphatic or they may be part of a ring structure.

Types of organic reactions- A chemical change involves a reorganization of the atoms in one or more substances. This process is represented by a chemical equation with the reactants on the left side of an arrow and the products on the right side 1. Addition. The double bond dissolves back to single bond and new bonds reach out to A and B whose bond is also dissolving. A_E – electrophylic addition – электрофильное присоединение A_N – nucleophylic addition – нуклеофильное присоединение. 2. Elimination (E) This is the opposite of addition i.e. a double bond is created when two groups on adjacent carbons are rejected by the molecule. The groups are just those groups which were added in the first place. The only one we cannot do is the elimination of H-H bond. 3. Substitution (S) One non-carbon group is replaced by another group. Usually only occurs at a singly bonded site. The only example so far is halogen/UV on alkanes but alkanols and haloalkanes love a bit of substitution as well. S_E – electrophylic substitution – электрофильное замещение S_N – nucleophylic substitution – нуклеофильное замещение 4. Condensation and Hydrolysis Condensation is where two molecules join together and lose a simple molecule. e.g. water or carbon dioxide. Hydrolysis is the reverse. 5. Oxidation and Reduction Are opposite of each other. Oxidation is either adding O or making it have a double bond or removing H or both. Reduction is the opposite. 6. Isomerization This is when a substance changes into another form with different properties but the same molecular formula. For example: n -pentane → iso -pentane The different forms are called “isomers”, and the phenomenon of the existence of different forms “isomerism”. Polymerization This is when a substance changes into another substance with the same composition but a much higher molecular mass. For example: nC₂H₄ethylene (monomer)→ (–CH₂–CH₂–)_n polyethylene (polymer)) The product of such a reaction is called a “polymer”, and the starting material the corresponding “monomer”. The term polymerization is also used for processes in which a polymer is formed, not from the monomer, but from other reactants of low molecular mass. This usage is somewhat misleading, but is well established.

Oligomerization This is similar to polymerization except that the product contains only a small number of monomer units. For example: 3C₂H₂ —heat, catalyst→ C₆H₆The degree of oligomerization is specified by the numerical prefixes di-, tri-, etc., as in dimer, trimerize, etc.

Substitution Reactions of Benzene Because of its greater stability than alkenes benzene tends to undergo substitution reactions rather than addition reactions (as do the alkenes). Nitration. Benzene reacts with a mixture of concentrated nitric and sulfuric acids to produce nitrobenzene as shown in the reaction below. The process is termed nitration. Sulfuric acid is the catalyst and the mixture must be warmed to about 500^оC to initiate the reaction Halogenation. Both bromine and chlorine react with benzene if iron is present. The actual catalyst is FeCl₃ or FeBr₃ (metallic iron also works as a catalyst because it reacts with halogens to produce the above salts). Alkylation (Friedel-Crafts reaction) Substitution of an alkyl group onto a benzene ring is called alkylation. The reaction is very similar to halogenations except that aluminum chloride is used to catalyze the reaction, as shown in the reaction below. In general alkyl halide RX is used in the substitution to produce an alkyl-benzene.

Aromatic hydrocarbons. Benzene and derivatives of benzene. These are compounds that contain the benzene ring as part of their structure.Benzene is used mainly as an intermediate to make other chemicals. About 80% of benzene is consumed in the production of three chemicals, ethylbenzene, cumene, and cyclohexane. Its most widely produced derivative is ethylbenzene, precursor to styrene, which is used to make polymers and plastics. In laboratory research, toluene is now often used as a substitute for benzene. The solvent-properties of the two are similar, but toluene is less toxic and has a wider liquid range. Benzene represents a special problem in that, to account for the bond lengths quantitatively, there must either be electron delocalization (molecular orbital theory) or a spin coupling of the p-orbitals (valence bond theory)

Nomenclature of Aromatic Compounds For molecules having alkyl groups or other simple substituents attached to the benzene ring benzene is used as the parent name and the attached groups are named in alphabetical order before it. If more than one substituent is attached to the benzene ring, their locations are specified by numbers. The lowest possible numbers are used and the substituents are named in alphabetical order. When only two substituents are present the prefixes ortho-, meta- and para are used in place of 1, 2-, 1, 3- and 1, 4- respectively. Ortho-, meta- and para- are generally abbreviated to o-, m- and p- in most cases. Benzene derivatives have from one to six substituents attached to the central benzene core. Examples of benzene compounds with just one substituent are phenol, which carries a hydroxyl group, and toluene with a methyl group. When there is more than one substituent present on the ring, their spatial relationship becomes important for which the arene substitution patterns ortho, meta, and para are devised. For example, three isomers exist for cresol because the methyl group and the hydroxyl group can be placed next to each other (ortho), one position removed from each other (meta), or two positions removed from each other (para). Xylenol has two methyl groups in addition to the hydroxyl group, and, for this structure, 6 isomers exist

Heterocyclic and polyaromatic hydrocarbons. Polyaromatic hydrocarbons. Polyaromatic hydrocarbons (PAH s), also known as polycyclic aromatic hydrocarbons or polynuclear aromatic hydrocarbons are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). As a pollutant, they are of concern because some compounds have been identified as carcinogenic, mutagenic, and teratogenic. PAHs are also found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish.

Fundamentals of biochemistry. Types of biomolecules. Biochemistry, sometimes called biological chemistry, is the study of chemical processes within and relating to, living organisms. By controlling information flow through biochemical signaling and the flow of chemical energy through metabolism, biochemical processes give rise to the complexity of life. Over the last 40 years, biochemistry has become so successful at explaining living processes that now almost all areas of the life sciences from botany to medicine are engaged in biochemical research. Today, the main focus of pure biochemistry is in understanding how biological molecules give rise to the processes that occur within living cells, which in turn relates greatly to the study and understanding of whole organisms.Proteins

Белки) Proteins are large biological molecules, or macromolecules, consisting of one or more chains of amino acid residues.Lipids(Липиды) Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others.Carbohydrates(Углеводы) A carbohydrate is a large biological molecule, or macromolecule, consisting only of carbon (C), hydrogen (H), and oxygen (O), usually with a hydrogen: oxygen atom ratio of 2: 1 (as in water); in other words, with the empirical formula Cm(H2O)n (where m could be different from n).Nucleic acids(Нуклеиновые кислоты) Nucleic acids are polymeric macromolecules, or large biological molecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides.Vitamines(Витамины) A vitamin is an organic compound required by an organism as a vital nutrient in limited amounts. An organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and on the particular organismEnzymes(Ферменты) Enzymes are large biological molecules responsible for the thousands of metabolic processes that sustain life. They are highly selective catalysts, greatly accelerating both the rate and specificity of metabolic reactions, from the digestion of food to the synthesis of DNA. Most enzymes are proteins.

Carbohydrates. Carbohydrate Classification There are a variety of interrelated classification schemes. The most useful classification scheme divides the carbohydrates into groups according to the number of individual simple sugar units. Monosaccharides contain a single unit; disaccharides contain two sugar units; and polysaccharides contain many sugar units as in polymers - most contain glucose as the monosaccharide unit. Monosaccharides: Glucose, Galactose, Fructose, Ribose, Glyceraldehyde. Disaccharides: Sucrose, Maltose, Lactose Polysaccharides: Starch, Glycogen, Cellulose. Functional Groups Aldoses contain the aldehyde group - Monosaccharides in this group are glucose, galactose, ribose, and glyceraldehyde. Ketoses contain the ketone group - The major sugar in this group is fructose. Reducing: Contain a hemiacetal or hemiketal group. Sugars include, glucose, galactose, fructose, maltose, lactose Non-reducing: Contain no hemiacetal groups. Sucrose and all polysaccharides are in this group. Monosaccharides: Monosaccharides are formed by a single molecule. It means that when hydrolyzed they can not release simpler molecules. Examples of this group of carbohydrates are glucose, ribose and fructose, among others. Oligosaccharides. They are formed by 2-9 monomers linked through glycosidic linkages; in other words, when hydrolyzed these compounds release 2 to 9 monosaccharides (some texts say up to 20; in fact, oligosaccharides release “a few” monosaccharides). Polysaccharides: Polysaccharides are carbohydrates formed by more than 9 monosaccharides (some texts say more than 10 monosaccharides, other texts say more than 20…in fact, they usually are formed by a lot of monosaccharides!). When the polysaccharides are formed by the same type of monosaccharides, they are called homopolysaccharides.

Amino acids. Proteins and its structure. Enzymes. Amino acids are biologically important organic compounds composed of amine (-NH₂) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, though other elements are found in the side-chains of certain amino acids. Proteinogenic amino acids are amino acids that are precursors to proteins, and are produced by cellular machinery coded for in the genetic code of any organism. There are 22 standard amino acids, but only 21 are found in eukaryotes. Of the 22, selenocysteine and pyrrolysine are incorporated into proteins by distinctive biosynthetic mechanisms. The other 20 are directly encoded by the universal genetic code. Humans can synthesize 11 of these 20 from each other or from other molecules of intermediary metabolism. The other 9 must be consumed (usually as their protein derivatives) in the diet and so are thus called essential amino acids. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine Protein structure is the biomolecular structure of a protein molecule. Each protein is a polymer – specifically a polypeptide – that is a sequence formed from various L-α -amino acids (also referred to as residues) vitamins. A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. An organic chemical compound is called a vitamin when the organism cannot synthesize the compound in sufficient quantities, and must be obtained through the diet; thus, the term " vitamin" is conditional upon the circumstances and the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animal organisms.Vitamin A (Retinol)- Cod liver oil; Vitamin B₁ (Thiamine)-Rice bran; Vitamin C (Ascorbic acid)-Citrus, most fresh foods; Vitamin D (Calciferol)- Cod liver oil; Vitamin E) (Tocopherol)- Wheat germ oil, unrefined vegetable oils; Vitamin B₂ (Riboflavin)-Meat, dairy products, eggs. Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C).

Аlkaloids and hormones. Alkaloids are a group of naturally occurring chemical compounds, that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure are also attributed to alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and more rarely other elements such as chlorine, bromine, and phosphorus.Contains nitrogen - usually derived from an amino acid. Bitter tasting, generally white solids (exception - nicotine is a brown liquid). They give a precipitate with heavy metal iodides: Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer's reagent (potassiomercuric iodide solution). Cream coloured precipitate. Dragendorff's reagent (solution of potassium bismuth iodide) gives orange coloured precipitate with alkaloids. Caffeine, a purine derivative, does not precipitate like most alkaloids. Alkaloids are basic - they form water soluble salts. Most alkaloids are well-defined crystalline substances which unite with acids to form salts. In plants, they may exist in the free state, as salts or as N-oxides. Occur in a limited number of plants. Nucleic acid exists in all plants, whereas, morphine exists in only one plant species.Alkaloids can be classified; in terms of their BIOLOGICAL activity, CHEMICAL structure (nucleus containing nitrogen), BIOSYNTHETIC pathway (the way they are produced in the plant). HORMONES A hormone is a class of regulatory biochemicals produced in particular parts of organisms by specific cells, glands, and/or tissues and then transported by the bloodstream to other parts of the body, with the intent of influencing a variety of physiological and behavioral activities, such as the processes of digestion, metabolism, growth, reproduction, and mood control. Hormonal signaling involves the following: Biosynthesis of a particular hormone in a particular tissue. Storage and secretion of the hormone. Transport of the hormone to the target cell(s). Recognition of the hormone by an associated cell membrane or intracellular receptor protein. Relay and amplification of the received hormonal signal via a signal transduction process: This then leads to a cellular response. The reaction of the target cells may then be recognized by the original hormone-producing cells, leading to a down-regulation in hormone production. This is an example of a homeostatic negative feedback loop. Those classes of hormones are found too in other groups of animals. In insects and crustaceans, there is a hormone with an unusual chemical structure, compared with other animal hormones, the juvenile hormone, a sesquiterpenoid

Nucleic acids. RNA. DNA. Nucleic acids are polymolecules, or large biomolecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides. Each nucleotide has three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is deoxyribose, the polymer is DNA. If the sugar is ribose, the polymer is RNA.Nucleic acids were discovered by Friedrich Miescher in 1869. Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses).Ribonucleic acid (RNA) functions in converting genetic information from genes into the amino acid sequences of proteins. The three universal types of RNA include transfer RNA (tRNA), messenger RNA (mRNA), and ribosomal RNA (rRNA).

Analytical chemistry is one of the chemical disciplines. Analytical chemistry is united with other chemical sciences with common chemical laws and based on studying of chemical properties of substances. Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample, and quantitative analysis determines the amount of certain components in the substance. The separation of components is often performed prior to analysis. Analytical chemistry is the chemical science about: – theoretical base of chemical analysis of substances; – method of detection and identification of chemical elements; – methods of qualitative determination of substances; – methods of selection (separation) of chemical elements and its compounds; – methods of establishing the structure of chemical compounds. Subjects of analytical chemistry are: chemical elements and its compounds and processing of transformation of substances in run chemical reactions. Aims of analytical chemistry are: 1. Establishing the chemical composition of analyzed object (isotopic, elementary, ionic, molecular, phase) – qualitative analysis. Qualitative analysis consist from – identification – establishing of identity of researched chemical compounds with well-known substance due to compare its physical and chemical properties – and detection – checking the presence in analyzed objects some components, impurities, functional groups etc. 2. Determination of content (amount and concentration) some components in analyzed objects – quantitative analysis. 3. Determination (establishing) of structure of chemical compound – nature and number of structural elements, its bonds one to another, disposition in space. 4. Detection of heterogeneity on surface or in volume of solids, distribution of elements in layers. 5. Research process in time: establishing character, mechanism and rate of molecular regrouping.6. Developing of present analytical methods theory, working out the new methods of analysis.

The role of analytical chemistry. Analytical chemistry is applied throughout industry, medicine, and all the sciences. To illustrate, consider a few examples. The concentrations of oxygen and of carbon dioxide are determined in millions of blood samples every day and used to diagnose and treat illnesses. Quantities of hydrocarbons, nitrogen oxides, and carbon monoxide present in automobile exhaust gases are measured to determine the effectiveness of emission-control devices. Quantitative measurements of ionized calcium in blood serum help diagnose parathyroid disease in humans. Quantitative determination of nitrogen in foods establishes their protein content and thus their nutritional value. The interdisciplinary nature of chemical analysis makes it a vital tool in medical, industrial, government, and academic laboratories throughout the world.

Analytical chemistry achieves the aims by various methods of analysis: I. Physical – determination of components of investigated substances without chemical reactions (destroying of sample): 1.Spectral analysis – investigation of emission and absorption spectra.2. Fluorescence analysis – investigation of luminescence, caused action of UV-radiation. 3. Roentgen-structural analysis – using X-ray.4.Mass-spectra analysis.5.Densimetry – measurement of density. II. Instrumental (physical-chemical) – based on measurement of physical parameters (properties) of substances in run of chemical reaction. This method divides on 1.Electrochemical– measurement of electrical parameters of electrochemical reactions. 2. Optical – investigation the influence of various electromagnetic radiation on substance.3.Thermal (heating) – investigation the changes the properties of substance by heat (undergo) action. III. Chemical – measurement of chemical bonds energy.Chemical analysis has some steps: 1. Sampling. 2. Dissolving the sample (in water, acid or alkali).3. Executing (running) the chemical reaction X + R → P.4. Measurement of definite parameter. In accordance to analytical reaction (X + R → P) applies three groups of chemical analysis methods: Measurement of amount (quantity) of reaction product P: mass, physical properties. Measurement of amount of reagent R that interacted with determined substance: volume of solution reagent R with known concentration. Registration changes of substance X acting with reagent: measurement of gas volumes.

Chemical methods of analysis. Titration. Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Since volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant or titrator is prepared as a standard solution. A known concentration and volume of titrant reacts with a solution of analyte or titrand to determine concentration Procedure A typical titration begins with a beaker or Erlenmeyer flask containing a very precise volume of the analyte and a small amount of indicator placed underneath a calibrated burette or chemistry pipetting syringe containing the titrant. Preparation techniques Typical titrations require titrant and analyte to be in a liquid (solution) form. Though solids are usually dissolved into an aqueous solution, other solvents such as glacial acetic acid or ethanol are used for special purposes (as in petrochemistry). Concentrated analytes are often diluted to improve accuracy. Types of titrations There are many types of titrations with different procedures and goals. The most common types of qualitative titration are acid-base titrations and redox titrations. Acid–base titration Acid-base titrations depend on the neutralization between an acid and a base when mixed in solution. In addition to the sample, an appropriate indicator is added to the titration chamber, reflecting the pH range of the equivalence point. Redox titration Redox titrations are based on a reduction-oxidation reaction between an oxidizing agent and a reducing agent. A potentiometer or a redox indicator is usually used to determine the endpoint of the titration, as when one of the constituents is the oxidizing agent potassium dichromate. Complexometric titration Complexometric titrations rely on the formation of a complex between the analyte and the titrant. In general, they require specialized indicators that form weak complexes with the analyte. Complexometric titration Complexometric titrations rely on the formation of a complex between the analyte and the titrant. In general, they require specialized indicators that form weak complexes with the analyte. Endpoint and equivalence point Though equivalence point and endpoint are used interchangeably, they are different terms. Equivalence point is the theoretical completion of the reaction: the volume of added titrant at which the number of moles of titrant is equal to the number of moles of analyte, or some multiple thereof (as in polyprotic acids). Back titration Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated.

Instrumental analysis- Instrumental analysis is a field of analytical chemistry that investigates analytes using scientific instruments. Spectroscopy is the study of the interaction between matter and radiated energy. Mass spectrometry (MS) is an analytical technique that produces spectra (singular spectrum) of the masses of the atoms or molecules comprising a sample of material. Electroanalytical methods are a class of techniques in analytical chemistry which study an analyte by measuring the potential (volts) and/or current (amperes) in an electrochemical cell containing the analyte. Potentiometry Potentiometry passively measures the potential of a solution between two electrodes, affecting the solution very little in the process. The potential is then related to the concentration of one or more analytes. Coulometry Coulometry uses applied current or potential to completely convert an analyte from one oxidation state to another. In these experiments, the total current passed is measured directly or indirectly to determine the number of electrons passed Voltammetry Voltammetry applies a constant and/or varying potential at an electrode's surface and measures the resulting current with a three electrode system. This method can reveal the reduction potential of an analyte and its electrochemical reactivity. Polarography Polarography is a subclass of voltammetry that uses a dropping mercury electrode as the working electrode. Amperometry Amperometry is the term indicating the whole of electrochemical techniques in which a current is measured as a function of an independent variable that is, typically, time or electrode potential.

Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures. The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase. The various constituents of the mixture travel at different speeds, causing them to separate. The separation is based on differential partitioning between the mobile and stationary phases. Chromatography was first employed by Russian scientist Mikhail Tsvet in 1900. Column chromatography Column chromatography is a separation technique in which the stationary bed is within a tube. Planar chromatography is a separation technique in which the stationary phase is present as or on a plane. The plane can be a paper, serving as such or impregnated by a substance as the stationary bed (paper chromatography) or a layer of solid particles spread on a support such as a glass plate (thin layer chromatography). Paper chromatography Paper chromatography is a technique that involves placing a small dot or line of sample solution onto a strip of chromatography paper. The paper is placed in a jar containing a shallow layer of solvent and sealed. Thin layer chromatography (TLC) is a widely employed laboratory technique and is similar to paper chromatography. However, instead of using a stationary phase of paper, it involves a stationary phase of a thin layer of adsorbent like silica gel, alumina, or cellulose on a flat, inert substrate. Gas chromatography (GC), also sometimes known as gas-liquid chromatography, (GLC), is a separation technique in which the mobile phase is a gas. Gas chromatographic separation is always carried out in a column, which is typically " packed" or " capillary". Liquid chromatography Liquid chromatography (LC) is a separation technique in which the mobile phase is a liquid. Liquid chromatography can be carried out either in a column or a plane Supercritical fluid chromatography Supercritical fluid chromatography is a separation technique in which the mobile phase is a fluid above and relatively close to its critical temperature and pressure. Ion exchange chromatography Ion exchange chromatography (usually referred to as ion chromatography) uses an ion exchange mechanism to separate analytes based on their respective charges.

Law of mass action (LMA). K.Guldberg and P.Waage (1867) clearly stated the Law of Mass Action (sometimes termed the Law of Chemical Equilibrium) in the form: the rate of any chemical reaction is proportional to the product of the masses of the reacting substances, with each mass raised to a power equal to the coefficient that occurs in the chemical equation. “Active mass” was interpreted as concentration and expressed in moles per liter. The law of mass action is a reaction that states that the values of the equilibrium – constant expression K_c are constant for a particular reaction at a given temperature, whatever equilibrium concentrations are substitute

Application of the law of mass action- Chemically pure water conducts an electric current very poorly and has an electrical conductivity of 0.055 µS∙ cm^{− 1}. But nevertheless it has a measurable electrical conductivity that is explained by the slight dissociation of water into hydrogen and hydroxide ions (According to the theories of Svante Arrhenius): H₂O → H⁺ + OH^– The electrical conductivity of pure water can be used to calculate the concentration of hydrogen and hydroxide ions in water. Let us write an expression for the dissociation constant of water: We can rewrite this equation as follows: [H⁺]∙ [OH^–] = [H₂O]∙ K Replacing the product [H₂O]∙ K in the last equation with the new constant K_w, we have: [H⁺]∙ [OH^–] = K_wThe latter K_w is called the ion product of water (or ionization constant, dissociation constant, self-ionization constant). The K_w value is depended of temperature. For pure water at 25°C K_w=10^-14, we have [H⁺] = [OH^-] = 1·10^-7 mol/L. Hence, for this temperature: K_w = 10^-7 ∙ 10^-7 = 10^-14 Solutions in which the concentrations of the hydrogen ions and hydroxide ions are the same are called neutral solutions.