Plan: Chemistry and its tasks

1. Contributions of Uzbek scientists to science
SY Yunusov (1909–1991). Academician of UzFA, doctor of chemical sciences, professor. Author of more than 600 scientific articles, more than 100 inventions, more than 10 monographs. In 1969, he was awarded the title of "Hero of Labor". He was awarded a gold medal named after DIMen Deleyev. UzFA founded the Institute of Chemistry of Plant Substances and created the School of Chemistry of Plant Substances. He identified more than 2000 alkaloids in more than 3600 plants found in Uzbekistan.
NA Parpiyev (1931). Academician of UzFA, doctor of chemical sciences, professor. Honored scientist of Uzbekistan. Author of more than 700 articles, 11 monographs, 22 author certificates, 3 textbooks. His scientific works are devoted to the stereochemistry of coordination compounds, their structure. He developed a thermal method for the determination of molybdenum, rhenium, tungsten and mercury and for obtaining highly pure molybdenum. Sh.I. Salihov (1944). Academician of UzFA, doctor of biological sciences, professor. Honored scientist of Uzbekistan, author of more than 350 scientific articles, monographs, more than 100 patents. He created a scientific school about the chemical structure of proteins and their effect on the body. About 10 preparations of the scientist have been introduced into medical practice.
NR Yusupbekov (1940). Academician of UzFA, doctor of technical sciences, professor. Honored scientist of Uzbekistan. In the name of Beruni
Laureate of the state award. Author of more than 600 scientific articles, more than 30 inventions and several monographs. His scientific works belong to the field of chemical cybernetics, and he founded the scientific school of automation of production processes.
HU Usmanov (1916–1994). Academician of UzFA, doctor of chemical sciences, professor. A person of science and technology who served in Uzbekistan. Laureate of the State Prize of Uzbekistan named after Beruni. In 1951, he established a laboratory of polymer materials in the Republic. Under his leadership, a number of technological systems of cotton pulp production meeting the requirements of world standards were developed.
AA Abduvahobov (1941). Academician of UzFA, doctor of chemical sciences, professor. Author of more than 400 scientific articles, more than 20 inventions and 5 monographs. His scientific works belong to the fields of chemistry of elemental organic compounds, problems of fine organic synthesis, determination of the chemical nature of the mechanism of action of lower molecules bioregulators, spatial chemistry, he developed methods of synthesis of pheromones and introduced them to agriculture.
Atoms are the basic structural unit of matter. Although they are very small, their own
has dimensions. Their diameter is around 1 Å (1 Å=10-10 m). Currently, the Å measurement unit is being replaced by the nanometer. Where: (1Å= 0.10 nm; 1 nm = 1 · 10–9m). The absolute mass of atoms is a very small quantity. For example, the absolute mass of a hydrogen atom is 0.00000000000000000000000000167 kg or 1.67·10-27 kg. The absolute mass of a carbon atom is 19.93·10-27 kg. The use of this absolute mass magnitude in making calculations has its own difficulties
causes. Therefore, in chemistry, a relative physical quantity - the relative atomic mass of an element - is calculated. r - English relative - relative. Relative atomic mass is a quantity indicating how many times the mass of an atom of an element is 1/12 (one-twelfth) of the mass of an atom of 12C (carbon-12).
19.93·10-27kg 1/12 of the absolute mass of a carbon (126C) atom (---------- --------------- = 12 =1.66 ·10-27kg) and this quantity is called atomic mass unit (mab). 1 mab=1.66·10-27kg.
For example, with the absolute mass of an oxygen atom equal to 26.57·10-27 kg, its relative atomic mass is:
It is equal to 26.57·10-27 Ar(O) = -------------------------- = 16. So, an oxygen atom is 16 times heavier than 1/12 of the mass of a carbon atom - 1.66·10-27.
Relative atomic mass is a quantitative indicator of an element. The absolute mass of an atom is the actual mass of an atom of an element, which is equal to a very small mass unit.
Calculation of the mass fraction of elements in compounds
The mass fractions of the elements in the substance are expressed in decimals, mostly (%) percentages. Calculate the mass fractions of carbon and oxygen in the carbon dioxide CO2 involved in the photosynthesis process that occurs in the green leaves of plants.
Solution: We calculate the relative molecular mass of CO2:
Mr(CO2)=12·1 + 16·2=44.
We find the mass fraction of O in CO2:
Ar(O) n 2·16 32
w(O) =32/44 = 0.73 or 73%.
Mr(CO2) 44 44
We find the mass fraction of C in CO2:
w(C) = 12/44 = 0.27 or 27%.
Mr(CO2) 44
Answer: 73% O and 27% C.

1. When studying the conditions for many chemical reactions, the mass of the reacting substances is the reaction product.
it is determined to be equal to the mass of lots. Such phenomena were observed by our great ancestors Abu Rayhan Beruni, Abu Ali Ibn Sina and other thinkers in their laboratories during the heating operations in vessels with welded mouths. In 1748-1760, the Russian scientist MV Lomonosov also tried to explain this phenomenon by conducting an experiment in a flask with a welded mouth - a retort. In 1772-1789, the French scientist A. Lavoisier also observed that the total mass does not change in the experiments conducted in a closed container and realized that this is a unique innovation - a new law. Thus, one of the main laws of nature - the law of conservation of mass - was discovered. The total mass of substances undergoing a chemical reaction is equal to the total mass of the reaction products. A. Lavoisier made an important conclusion based on this law, stated that the atomic mass of each element participating in the reaction does not change during the reaction. This means that an atom of one element does not change into an atom of another element in a chemical reaction. In chemical reactions, atoms do not disappear, they do not come into existence from nothing, the total number of atoms does not change. The mass of each atom remains unchanged in chemical reactions. Therefore, the total mass of substances also remains unchanged. This law is considered one of the most important laws of nature. This law shows that we are not consumers by nature, but converters. When iron ores are mined from the ground and necessary items are prepared, the number of iron atoms on our planet does not decrease, but changes from one appearance to another. For example, things made of iron rust, as a result, even 50% of the spent iron will not be recovered. Of course, any chemical change can be made by spending the necessary energy. Fe + S= FeS was obtained for the reaction and was formed as a result of the reaction. The following law of nature follows from the law of conservation of mass: Substances do not exist from nothing, do not disappear from existence, only change from one form to another.


2. The volume of a certain amount of gas is not a constant quantity, it changes with changes in temperature (t) and pressure (P). In 1811, Professor A. Avogadro of the University of Turin, Italy, while studying phenomena related to gases, came to the following conclusion: Under the same conditions, the number of molecules in different gases of equal volume is equal. Later experiments confirmed this conclusion, and this law came to be known as Avogadro's law. Avogadro found that gaseous molecules of simple substances consist of two atoms (H2, O2, N2, F2, Cl2). Avogadro's law is specific for gases, solids and liquids do not obey this law. Because, at low pressures, the distance between molecules in gases is thousands of times larger than their own size. The volume of a gas depends on the number of molecules and the intermolecular distance. The size of moles is not important. The distance between the molecules of different gases at the same pressure and the same temperature is almost the same. Thus, under the same conditions, the same number of molecules of different gases occupy the same volume. The volume of liquid and solid substances depends not only on the number of molecules, but also on their size due to the small intermolecular distance. At extremely low temperatures or high pressures, gases resemble liquids, and Avogadro's law does not apply because the intermolecular distances approach the size of their molecules. As you know from the previous lessons (see § 10), one mole of any substance contains 6.02·1023 particles (molecules, atoms, ions). Therefore, according to Avogadro's law, any gas containing 6.02·1023 particles occupies the same volume under the same conditions. Let's calculate the volume occupied by 6.02·1023 particles of some gases under normal conditions (temperature 0°C, pressure 101.325 kPa). To do this, the molar mass of the gas - M is divided by its density (the mass of 1 m3 gas in kg under normal conditions) - r: Vm= M/r. So, 6.02·1023 particles (1 mole) of any gas occupy a volume of 0.0224 m3 or 22.4 l under normal conditions. The ratio of the volume of the substance to the amount of the substance is called the molar volume of this substance Vm, and it is expressed by the formula: Vm = V/n
is plowed. Using this formula, we can derive the formulas n = V/Vm, V = nVm. If the mass of the gas is given, its volume is found using the formula V = m · Vm/M. The molar volume of a gas is expressed in m3/mol or l/mol. Under normal conditions, 6.02·1023 molecules of liquid and solid substances occupy different volumes according to their densities. For example, 6.02·1023 molecules or 1 mole of liquid water occupy a volume of 0.018 l (density of water at 4°C is 1 g/ml).


3. The great thinker Abu Ali ibn Sina described simple and complex drugs in his book "The Laws of Medicine" and explained the first concepts about the constancy of the composition by explaining that any medicine has a certain composition. The law of constancy of composition proposed by the French scientist J. Proust in 1808 was widely recognized in 1809. Any chemical pure substance has a constant composition, regardless of the method and place of its extraction. For example, water is composed of hydrogen and oxygen (composition). The mass fraction of hydrogen in water is 11.11%, and the mass fraction of oxygen is 88.89% (quantitative ratio). Water can be obtained using different methods. Regardless of how it is obtained, pure water has the same composition and the same properties. Although hydrogen peroxide - H2O2 has the same quality as water, differs from water in its quantitative composition. In hydrogen peroxide, the mass fraction of hydrogen is 5.88%, and the mass fraction of oxygen is 94.12%. Hydrogen peroxide is a substance with very different properties from water. Changes in the quantity of atoms in a substance lead to changes in quality. Quantity and quality are always related. The English scientist Dalton expressed the opinion that "compounds are formed by combining a certain number of atoms of one element with a certain number of atoms of another element" (in other words, compounds are formed by a certain number of atoms of two or more elements from one person). . differs from water in its quantitative composition. In hydrogen peroxide, the mass fraction of hydrogen is 5.88%, and the mass fraction of oxygen is 94.12%. Hydrogen peroxide is a substance with very different properties from water. Changes in the quantity of atoms in a substance lead to changes in quality. Quantity and quality are always related. The English scientist Dalton expressed the opinion that "compounds are formed by combining a certain number of atoms of one element with a certain number of atoms of another element" (in other words, compounds are formed by a certain number of atoms of two or more elements from one person). When many elements are combined with each other, the ratio of the masses of these elements forms different compounds that have a specific value that differs from each other in each case. For example, carbon forms two different compounds with oxygen. One of them - carbon (II)-oxide (CO) contains 42.88% carbon and 57.12% oxygen. The second compound - carbon (IV)-oxide (CO2) contains 27.29% carbon and 72.71% oxygen. While studying such compounds, J. Dalton discovered the law of multiple proportions in 1803. If two elements form several chemical compounds with each other, the masses of other elements corresponding to the mass of one element in these compounds will be in the ratio of small integers.
References:

1. NI Bozorov, General chemistry. Tashkent: Sparks of literature. 2017.

2. Parpiev N.A., Rakhimov H.R., Muftakhov A.G. Theoretical foundations of inorganic chemistry. Tashkent: Uzbekistan. 2000


Websites:
1. www.chemistry.ru
2. www.Zionet.uz