The importance of reaction rates in analytical chemistry presentation. Chemistry presentation: “The rate of chemical reactions. Contact surface of reactants

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Chemical reaction rate

Research objectives: 1. Give a definition to the concept of the rate of a chemical reaction. 2. Experimentally identify the factors influencing the rate of a chemical reaction.

They go in the whole volume 2CO (g) + O 2 (g) = 2CO 2 (g) 2HBr (g) ↔H 2 (g) + Br 2 (g) NaOH (p) + HCl (p) = NaCl (p) + H 2 O (liquid) F (solid) + S (solid) = FeS (solid) Go to the interface CaCO 3 (solid) ↔CaO (solid) + CO 2 (gas) CO 2 (gas) + C ( s) = 2CO (g) 4H 2 O (l) + 3Fe (s) ↔4H 2 (g) + Fe 3 O 4 (s) Classification of reactions by phase composition

Average rate of a homogeneous reaction The rate of a homogeneous reaction is determined by a change in the concentration of one of the substances per unit time υ = - / + ΔC Δt mol l s

The average rate of a heterogeneous reaction is determined by the change in the amount of a substance that has entered into a reaction or formed as a result of a reaction per unit of time per unit of surface Interaction occurs only at the interface between substances S - surface area

Factors affecting the rate of a chemical reaction The nature of the reacting substances Concentration Temperature Catalyst, inhibitor Contact area The reaction occurs when molecules of reacting substances collide, its speed is determined by the number of collisions and their strength (energy)

The nature of the reacting substances The reactive activity of substances is determined: by the nature of chemical bonds, the rate is higher for substances with ionic and covalent polar bonds (inorganic substances), the rate is lower for substances with covalent low-polarity and non-polar bonds (organic substances) υ (Zn + HCl = H 2 + ZnCl 2 )> υ (Zn + CH 3 COOH = H 2 + Zn (CH3COO) 2 by their structure, the speed is higher for metals, which donate electrons more easily (with a large radius of the atom), the speed is higher for non-metals, which more easily accept electrons (with a smaller radius of the atom) υ (2K + 2 H 2 O = H 2 + 2KOH)> υ (2Na + 2 H 2 O = H 2 + 2NaOH)

Jacob Van't Hoff (1852-1911) Temperature increases the number of molecular collisions. Van't Hoff's rule (formulated on the basis of an experimental study of reactions) In the temperature range from 0 ° C to 100 ° C, with an increase in temperature for every 10 degrees, the rate of a chemical reaction increases 2-4 times: Van't Hoff's rule does not have the force of a law. Laboratory technology was imperfect, therefore: it turned out that the temperature coefficient in a significant temperature range is not constant, it was impossible to study both very fast reactions (occurring in milliseconds) and very slow (which require thousands of years) reactions involving large molecules of complex shapes (for example , proteins) do not obey the van't Hoff rule v = v 0  ∆ τ / 10 - van't Hoff temperature coefficient

Concentration For substances to interact, their molecules must collide. The number of collisions is proportional to the number of particles of reacting substances per unit volume, i.e. their molar concentrations. Law of mass action: The rate of an elementary chemical reaction is proportional to the product of the molar concentrations of reactants, raised to powers equal to their coefficients: 1867 K. Guldberg and P. Waage formulated the law of action masses a A + b B  d D + f F v = k C (A) a c (B) bk is the reaction rate constant (v = k at c (A) = c (B) = 1 mol / l)

Contact area The rate of a heterogeneous reaction is directly proportional to the contact surface area of ​​the reagents. When grinding and stirring, the contact surface of the reactants increases, while the reaction rate increases. The rate of a heterogeneous reaction depends on: a) the rate of supply of the reactants to the phase boundary; b) the rate of reaction at the interface, which depends on the area of ​​this surface; c) the rate of removal of reaction products from the phase boundary.

Profile level At "3" - §13 p.126-139, exercise. 1, p. 140. On “4” - §13 p.126-139, exercise 1.2, p.140. On “5” - §13 p.126-139, exercise 4.5, p.140. Basic level At “3” - §12 pp. 49-55, exercise. 5, p. 63. On “4” - §12 p. 49-55, task 1, p. 63. On “5” - §12 p. 49-55, task 2, p. 63.

Continue the phrase: "Today in the lesson I repeated ..." "Today in the lesson I learned ..." "Today in the lesson I learned ..."

http://www.hemi.nsu.ru/ucheb214.htm http://www.chem.msu.su/rus/teaching/Kinetics-online/welcome.html O.S. Gabrielyan. Chemistry. Grade 11. A basic level of. Textbook for general education educational institutions, M., Bustard, 2010 I. I. Novoshinsky, N.S. Novoshinskaya. Chemistry. Grade 10. Tutorial for educational institutions, M., "ONYX 21st century"; "Peace and Education", 2004 OS Gabrielyan, GG Lysova, AG Vvedenskaya. Chemistry teacher's handbook. Grade 11. M., Bustard. 2004 K.K. Kurmasheva. Chemistry in tables and diagrams. M., "New List". 2003 N.B. Kovalevskaya. Chemistry in tables and diagrams. M., "Publishing School 2000". 1998 P. A. Orzhekovsky, N. N. Bogdanova, E. Yu. Vasyukova. Chemistry. Collection of tasks. M. " Eksmo ", 2011 Photos: http://www.google.ru/ Literature:

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Multilevel group work on options on the topic "The rate of chemical reaction. Chemical equilibrium" ....

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Generalizing lesson on the topic “The rate of chemical reactions. Chemical equilibrium ". Purpose: Generalization of the theoretical knowledge of students about the rate of a chemical reaction, factors affecting soon ...

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Analytical reactions in solutions Analytical reactions in solutions, reversible and irreversible Chemical equilibrium Law of mass action, chemical equilibrium constant Factors affecting the displacement of the equilibrium of analytical reactions

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Types of chemical reactions in analytical chemistry acid-base reactions - reactions with proton transfer H + redox reactions (ORR) - reactions with electron transfer ē complexation reactions - reactions with the transfer of electron pairs and the formation of bonds by the donor-acceptor mechanism of the deposition reaction - heterogeneous reaction in solution

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Reversible reactions are widely used in quantitative analysis, i.e. proceeding simultaneously in two opposite directions: aA + bB ↔ cC + dD The reaction proceeding in the direction of the formation of reaction products is called direct aA + bB → cC + dD The reaction proceeding in the direction of the formation of the starting substances - reverse cC + dD → aA + bB In principle , all reactions occurring in nature are reversible, but in cases where the reverse reaction is very weak, the reactions are considered practically irreversible. These usually include those reactions in the course of which one of the resulting products leaves the reaction sphere, i.e. precipitate, are released in the form of a gas, a low-dissociable substance (for example, water) is formed, the reaction is accompanied by the release of a large amount of heat.

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The state of chemical equilibrium is characteristic only for reversible processes. In reversible reactions, the rate of the direct reaction initially has a maximum value, and then decreases due to a decrease in the concentration of the starting materials consumed in the formation of reaction products. The reverse reaction at the initial moment has a minimum rate, which increases as the concentration of the reaction products increases. Thus, the moment comes when the speeds of forward and backward reactions become equal. This state of the system is called chemical equilibrium kpr = krev

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In 1864 - 1867, the Norwegian scientists Guldberg and Vaage established the law of effective masses (they meant concentrations by acting masses. Then the term concentration was not yet known, it was introduced later by Van't Hoff): the rate of a chemical reaction is directly proportional to the product of the concentrations of reactants in powers, equal to the corresponding stoichiometric coefficients. For a reversible reaction of the type aA + bB = cC + dD, according to the law of mass action, the speeds of the forward and reverse reactions are respectively equal: vpr = kpr [A] a [B] v, vrev = krev [C] c [D] d. If vpr = vrev, then kpr [A] a [B] in = krev [C] c [D] d, whence K = krev / kpr = [C] c [D] d / [A] a [B] in ... Thus, the equilibrium constant is the ratio of the product of the concentrations of the reaction products to the product of the concentrations of the initial substances. The equilibrium constant is a dimensionless quantity, since depends on the concentration and amount of substances.

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The value of K, which characterizes the constancy of the equilibrium concentration ratios of reagents at a constant temperature, was called the equilibrium constant by Van't Hoff. The equilibrium constant is one of the quantitative characteristics of the state of chemical equilibrium. Task: write an expression for the equilibrium constant of the following reactions: H2 + I2 ↔ 2HI; K = 2 / N2 + 3H2 ↔ 2NH3; K = 2/3

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The direction of the displacement of chemical equilibrium with changes in concentration, temperature and pressure is determined by the Le Chatelier principle: if an effect is made on a system in equilibrium (change in concentration, temperature, pressure), then the equilibrium in the system shifts towards weakening this effect LE CHATELIER Henri Louis

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For the reaction A + B ↔ C + D Change in concentration If the concentration of the starting materials increases, then the equilibrium shifts towards the formation of reaction products, i.e. to the right A + B → C + D, if the concentration of the starting substances decreases, then the equilibrium shifts towards the starting substances, i.e. to the left A + B ← C + D if the concentration of the reaction products increases, then the equilibrium shifts towards the formation of the initial substances, i.e. to the left A + B ← C + D, if the concentration of reaction products decreases, then the equilibrium shifts towards the formation of reaction products, i.e. to the right, A + B → C + D

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For the reaction A + B ↔ C + D 2) The change in temperature is determined by the heat effect of the reaction during an exothermic process (negative value of the reaction) - if the temperature decreases, then the equilibrium shifts towards the formation of reaction products, i.e. to the right A + B → C + D, if the temperature increases, then the equilibrium shifts towards the starting substances, i.e. to the left A + B ← C + D in an endothermic process (positive value of the reaction) - if the temperature increases, then the equilibrium shifts towards the formation of reaction products, i.e. to the right A + B → C + D, if the temperature decreases, then the equilibrium shifts towards the formation of the initial substances, i.e. left A + B ← C + D

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CLASSIFICATION OF CHEMICAL REACTIONS BY PHYSICITY (AGGREGATE STATE) CHEMICAL REACTIONS HOMOGENEOUS HETEROGENEOUS (reactants and reaction products are in the same phase) 2SO2 (g) + O2 (g) = 2SO3 (g) HCl (g) + NaCl (g) + H2O Feature: they occur throughout the entire volume of the reaction mixture (reactants and reaction products are in different phases) S (solid) + O2 (g) = SO2 (g) Zn (solid) + 2HCl (g) = ZnCl2 ( g) + H2 (d) Feature: flow at the interface

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RATE OF REACTIONS Rate of homogeneous reaction Rate of heterogeneous reaction A (g) + B (g) = C (g) ∆V = V2-V1 ∆ t = t2-t1 V (hom) = ∆V / (∆ t * V) C = V / V (mol / l) V (gom) = ± ∆С / ∆ t (mol / l * s) V (het) = ± ∆V / (S * ∆ t) (mol / m ^ 2 * s)

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Factors affecting the rate of chemical reaction Concentration A + B = C + D V = k [A] * [B] Nature of reactants Contact surface area temperature catalyst

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Problem 1 At some point in time, the chlorine concentration in the vessel, in which the reaction H2 + Cl2 = 2HCl occurs, was 0.06 mol / L. After 5 sec. The chlorine concentration was 0.02 mol / L. What is the average rate of this reaction in the specified period of time? Given C1 (Cl2) = 0.06 mol / L C2 (Cl2) = 0.02 mol / L ∆ t = 5 sec V =? Solution H2 + Cl2 = 2HCl V = - (C2 - C1) / ∆ t = (0.02-0.06) / 5 = 0.008 (mol / L * s) Answer: V = 0.008 (mol / L * s)

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Problem 2 How will the rate of the reaction FeCl3 + 3KCNS = Fe (CNS) 3 + 3KCl change in an aqueous solution when the reaction mixture is diluted twice with water Given C (ions)< 2 раза V2/V1=? Решение Fe(3+) + 3CNS(-) = Fe(CNS)3 V =k*^3 пусть до разбавления: х = Y = ^3 В результате разбавления концентрация ионов уменьшается: x/2 = y/2 = V2/V1 = k*(x/2)*(y/2)^3 = 16 Ответ: V2/V1 = 16 ^3 – в степени 3

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Problem 3 How will the reaction rate change when the temperature rises from 55 to 100 ° C, if the temperature coefficient of the rate of this reaction is 2.5? Given γ = 2.5 t1 = 55 't2 = 100' Vt2 / Vt1 =? Solution = 2.5 * ((100-55) / 10) = = 25 ^ 4.5 = (5/2) ^ 9/9 = 43.7 Answer: the reaction rate increases 43.7 times

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Problem 4 When the temperature rises by 30 ° C, the rate of some reaction increases by 64 times. What is the temperature coefficient of the rate of this reaction? Given Vt2 / Vt1 = 64 t2 = 30 ’γ =? Solution = γ ^ 3 64 = γ ^ 3 γ = 4 Answer: the temperature coefficient of the reaction rate is 4.

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Test: consolidation of knowledge 1. To reduce the reaction rate, it is necessary to: a) increase the concentration of reactants b) introduce a catalyst into the system c) increase the temperature d) lower the temperature 2. The reaction proceeds at the highest rate: a) neutralization b) sulfur burning in air in ) dissolution of magnesium in acid d) reduction of copper oxide with hydrogen 3. Indicate the homogeneous reaction. a) CaO + H2O = Ca (OH) 2 b) S + O2 = SO2 c) 2CO + O2 = 2CO2 d) MgCO3 MgO + CO2 4. Indicate the heterogeneous reaction. a) 2CO + O2 = 2CO2 b) H2 + Cl2 = 2HCl c) 2SO2 + O2 = 2SO2 (cat V2O5) d) N2O + H2 = N2 + H2O 5. Note which reaction is both homogeneous and catalytic. a) 2SO2 + O2 = 2SO3 (cat NO2) b) CaO + CO2 = CaCO3 c) H2 + Cl2 = 2HCl d) N2 + 3H2 = 2NH3 (cat Fe)

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Test: consolidation of knowledge 6. Indicate how the rate of the bimolecular gas reaction 2NO2 = N2O4 will change with an increase in NO2 concentration by three times. a) increase by 3 times b) decrease by 6 times c) increase by 9 times d) increase by 6 times 7. Indicate which process corresponds to the expression of the law of mass action for the rate of chemical reaction V = k ^ x. a) S + O2 = SO2 b) 2H2 + O2 = 2H2O c) 2CO + O2 = 2CO2 d) N2 + O2 = 2NO 8. Note which process speed will not change if the pressure in the reaction vessel is increased (t without change). a) 2NO + O2 = 2NO2 b) H2 + Cl2 = 2HCl c) CaO + H2O = Ca (OH) 2 d) N2O4 = 2NO2 9. Calculate what the temperature coefficient of the reaction rate is if, when the temperature drops by 40'C, it speed decreased 81 times.

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State budget educational institution higher vocational education"Kazan State Medical University" of the Ministry of Health Russian Federation MEDIKO-PHARMACEUTICAL COLLEGE History of the development of analytical chemistry Completed by: Davletshina Gulnaz R group

Analytical chemistry is the science of methods for determining the chemical composition of a substance and its structure. However, this definition of COP appears to be exhaustive. The subject of analytical chemistry is the development of analytical methods and their practical implementation, as well as a broad study of theoretical foundations. analytical methods... This includes studying the forms of existence of elements and their compounds in various media and states of aggregation, determining the composition and stability of coordination compounds, optical, electrochemical and other characteristics of a substance, studying the rates of chemical reactions, determining the metrological characteristics of methods, etc. new methods of analysis and the use of modern advances in science and technology for analytical purposes.

Depending on the task, the properties of the analyte and other conditions, the composition of the substances is expressed in different ways. Chemical composition substances can be characterized by the mass fraction (%) of elements or their oxides or other compounds, as well as by the content of individual chemical compounds or phases, isotopes, etc. actually present in the sample. The composition of alloys is usually expressed by the mass fraction (%) of the constituent cements; composition rocks, ores, minerals, etc. the content of elements in terms of any of their compounds, most often oxides.

Theoretical basis analytical chemistry is constituted by the fundamental laws of natural science, such as the periodic law of D.I. electrochemistry, chemical thermodynamics, solution theory, metrology, information theory and many other sciences.

Analytical chemistry is of great scientific and practical importance. Almost all basic chemical laws were discovered using the methods of this science. The composition of various materials, products, ores, minerals, lunar soil, distant planets and other celestial bodies was established by the methods of analytical chemistry, the discovery of a number of elements of the periodic table was made possible thanks to the use of precise methods of analytical chemistry. The importance of analytical chemistry

Many practical techniques of analytical chemistry and analytical techniques were known in ancient times. This is, first of all, assay art, or assay analysis, which was carried out "dry", that is, without dissolving the sample and using solutions. The methods of assay analysis controlled the purity of noble metals and established their content in ores, alloys, etc. The technique of performing assay analysis was reproduced in laboratory conditions manufacturing process obtaining precious metals. These methods of analysis were used in Ancient Egypt and Greece, they were also known in Kievan Rus. Practical value reactions in solution were small at that time. The main stages of the development of analytical chemistry

Industrial development and various industries by the middle of the 17th century. demanded new methods of analysis and research, since assay analysis could no longer meet the needs of chemical and many other industries. By this time, by the middle of the 17th century. usually include the emergence of analytical chemistry and the formation of chemistry itself as a science. Determination of the composition of ores, minerals and other substances aroused great interest, and chemical analysis became at this time the main research method in chemical science. R. Boyle () developed general concepts about chemical analysis. He laid the foundations for modern qualitative analysis by the "wet" method, that is, by carrying out reactions in solution, led the system of qualitative reactions known at that time and proposed several new ones (for ammonia, chlorine, etc.), applied litmus for the detection of acids and alkalis and made other important discoveries.

M.V. Lomonosov () first began to systematically use scales in the study of chemical reactions. In 1756, he experimentally established one of the fundamental laws of nature, the law of conservation of mass of matter, which formed the basis of quantitative analysis and is of great importance for all science. MV Lomonosov developed many methods of chemical analysis and research that have not lost their significance to this day (filtration under vacuum, operations of gravimetric analysis, etc.). MV Lomonosov's merits in the field of analytical chemistry include the creation of the foundations of gas analysis, the use of a microscope for qualitative analysis of the shape of crystals, which later led to the development of microcrystalloscopic analysis, the design of a refractometer and other devices. MV Lomonosov summarized the results of his own research and the experience of a research chemist, analyst and technologist in his book "The First Foundations of Metallurgy or Ore Mining" (1763), which had a tremendous impact on the development of analytical chemistry and related fields, as well as metallurgy and ore mining.

The use of precise methods of chemical analysis made it possible to determine the composition of many natural substances and products of technological processing, to establish a number of basic laws of chemistry. A.L. Lavoisier () determined the composition of air, water and other substances and developed the oxygen theory of combustion. Based on analytical data, D. Dalton () developed the atomistic theory of matter and established the laws of constancy of composition and multiple ratios. J.L. Gay-Lussac () and A. Avogadro () formulated gas laws.

M.V. Severgin () proposed a colorimetric analysis based on the dependence of the color intensity of a solution on the concentration of a substance, J.L. Gay-Lussac developed a titrimetric method of analysis. These methods, together with gravimetric methods, formed the basis of classical analytical chemistry and have retained their importance to this day. Analytical chemistry, enriched with new methods, continued to develop and improve. At the end of the 18th century. T.E. Lovits (), developing the ideas of M.V. Lomonosov, created microcrystalloscopic analysis, a method for the qualitative analysis of salts by the shape of their crystals.

At the end of the 18th and 19th centuries. by the works of many scientists T.U. Bergman (), L. J. Tenard (), K. K. Klaus () and others, a systematic qualitative analysis... In accordance with the developed scheme, from the analyzed solution, the action of group reagents was used to precipitate certain groups elements, and then within these groups the discovery of individual elements was carried out. This work was completed by K.R. Fresenius (), who wrote textbooks on quality and quantitative analysis and founded the first journal of analytical chemistry (Zeitschrift fur analytische Chemie, now Fresenius Z. anal. Chem.). At the same time, I. Ya. Berzelius () and Yu. Liebig () improved and developed methods for the analysis of organic compounds for the content of the main elements C, H, N, etc. Titrimetric analysis progresses noticeably, methods of iodometry, permanganatometry, etc. the discovery is made in the years. R.V.Bunsen () and G.R. Kirchhoff (). They propose spectral analysis, which is becoming one of the main methods of analytical chemistry, continuously evolving to the present day.

The discovery of the periodic law in 1869 by DI Mendeleev () had a tremendous influence on the development of chemistry and other sciences, and DI Mendeleev's "Fundamentals of Chemistry" became the basis for the study of analytical chemistry. The creation of the theory of the structure of organic compounds by A.M.Butlerov was also of great importance. A significant influence on the formation of analytical chemistry and its teaching was exerted by A.A. english languages... In 1868, on the initiative of D.I. Mendeleev and N. A. Menshutkin, the Russian Chemical Society was established at St. Petersburg University, which in 1869 began to publish its own journal. The creation of the Scientific Chemical Society and the publication of the journal had a beneficial effect on the development of domestic chemistry and analytical chemistry in particular.

A special section of chemistry was developed by NS Kurnakov () physicochemical analysis, based on the study of diagrams "composition property". The method of physicochemical analysis makes it possible to establish the composition and properties of compounds formed in complex systems, according to the dependence of the properties of the system on its composition, without isolating individual compounds in a crystalline or other form.

In 1903 M.S. Tsvet () proposed chromatographic analysis effective method separation of compounds with similar properties, based on the use of adsorption and some other properties of the substance. The advantages of this method were fully appreciated only a few decades after its discovery. A. Martin and R. Sing were awarded the Nobel Prize in 1954 for the development of partition chromatography.

Further development of the theory of analytical chemistry is associated with the discovery by N.N. Beketov () of the equilibrium character of chemical reactions and K.M. Guldberg () and II. Waage () of the law of the acting masses. With the appearance in 1887 of the theory of electrolytic dissociation by S. Arrhenius (), analytical chemists obtained a method of effective quantitative control of chemical reactions, and the successes of chemical thermodynamics further expanded these possibilities. An essential role in the development of the scientific foundations of analytical chemistry was played by the monograph by V. Ostwald () "Scientific foundations of analytical chemistry in an elementary presentation", published in 1894. The works of L.V. Pisarzhevsky () and N. A. Shilova () on the electronic theory of redox processes.

Since the 20s of the XX century. quantitative emission spectral analysis and absorption spectroscopy begin to develop intensively. Devices with photoelectric recording of light intensity are being designed. In 1925, Y. Geyrovsky () developed polarographic analysis, for which in 1959 he was awarded the Nobel Prize. In the same years, chromatographic, radiochemical and many other methods of analysis were developed and improved. Since 1950, the method of atomic absorption spectroscopy proposed by E. Walsh has been rapidly developing.

The development of industry and science has demanded new and sophisticated methods of analysis from analytical chemistry. The need arose for the quantitative determination of impurities at the level and below. It turned out, for example, that the content of the so-called forbidden impurities (Cd, Pb, etc.) in the materials of rocket technology should be no higher than 10 ~ 5%, the content of hafnium in zirconium used as a structural material in nuclear technology should be less than 0, 01%, and in materials of semiconductor technology impurities should be no more than 10%. It is known that the semiconducting properties of germanium were discovered only after samples of this element of high purity were obtained. Zirconium was initially rejected as a structural material in nuclear industry on the grounds that he himself quickly became radioactive, although according to theoretical calculations this should not have been. Later it turned out that it was not zirconium that became radioactive, but the usual companion of zirconium, hafnium, which is in the form of an impurity in zirconium materials.

The present day of analytical chemistry is characterized by many changes: the arsenal of methods of analysis is expanding, especially in the direction of physical and biological; automation and mathematization of analysis; creation of techniques and means of local, non-destructive, remote, continuous analysis; approach to solving problems on the forms of existence of components in the analyzed samples; the emergence of new opportunities for increasing the sensitivity, accuracy and speed of analysis; further expansion of the range of analyzed objects. Computers are now widely used, lasers are doing a lot, laboratory work has appeared; the role of analytical control, especially the objects of our environment, has significantly increased. Interest in the methodological problems of analytical chemistry has increased. How to clearly define the subject of this science, what place it occupies in the system of scientific knowledge, whether it is fundamental or applied, what stimulates its development, these and similar questions have been the subject of many discussions.