Consider the basic chemical formulas of substances. It is customary to isolate mixtures and pure substances. If the former suggest the presence of several components, each of which retains individual properties, then pure substances do not imply the presence of any impurities. Let us analyze the basic chemical formulas for solving problems proposed by graduates of primary and secondary schools.
Classification
To begin with, there is a division of compounds into simple and complex substances. The main chemical reactions considered in the chemistry course of grades 8–9 relate to water, oxygen, and hydrogen. Let us dwell on them in more detail.
Water
Considering the basic chemical formulas, one cannot ignore the compound without which human existence is impossible. 2 - not only high school students know this formula, but also children from elementary school. The molecule contains two hydrogen atoms and one oxygen atom, interconnected by a covalent polar chemical bond.
Water is necessary for metabolic processes, it is an active compound that interacts with simple and complex organic and inorganic substances.
Oxygen
Studying the basic chemical formulas as part of the school curriculum, the consideration of O 2 is mandatory. This simple substance with a covalent non-polar bond formed by two hydrogen atoms is necessary for living things to breathe. Molecular oxygen also takes an active part in combustion reactions, forming several products with proteins, fats, carbohydrates: carbon monoxide (4) and water.
The main chemical reactions during the combustion of saturated and unsaturated hydrocarbons are the basis for leaving the design problems. We give one of the examples from the course of class 10 of organic chemistry. Suppose it is necessary to determine the volume of gas that is required for the complete combustion of 30 liters of methane gas. In order to cope with the task, the equation of the proceeding interaction is written first, the coefficients are placed:
CH 4 + 2O 2 = CO 2 + 2H 2 O
Further, a proportion is compiled taking into account the fact that, according to the Avogadromo law, molar relations will be equal to voluminous. Next, mathematical calculations are performed.
Silver
When analyzing simple substances, it is necessary to dwell on some of them. In particular, a metal such as silver is of interest. Since olden times, it attracted people with its brilliance, insignificant reactivity. For several centuries, it was silver that was used to disinfect drinking water. This method formed the basis for the creation of modern household filters designed to remove microorganisms from drinking water. In nature, it is in the form of nuggets. So, there are references to the fact that in the 15th century a silver nugget with a weight of 20 tons was found at the St. George mine.
In nature, there are silver ores (in which about 50% of the metal itself), as well as polymetallic complex compounds (no more than 15% of silver in them). There are similar ores in Japan, Bolivia, USA, Peru, Australia, Canada.
This is a ductile metal of silver white color (with high electrical conductivity) and has bactericidal properties. In our country, the maximum concentration limit for silver in drinking water is established by the norms of the Sanitary and Hygienic Control, it is 0.05 mg / l. In the Middle Ages, this metal was given magical properties: protection from evil forces, vampires, demons. If a person’s silver products were dark, it was believed that he was terminally ill. This metal is used in electronics, jewelry, photography, electrical engineering, medicine.
Sulfuric acid
Considering the basic chemical formulas of inorganic substances that schoolchildren should know, this oxygen-containing acid cannot be ignored. The feedstock for its production is pyrite (FeS 2 ), hydrogen sulfide (H 2 S), crystalline sulfur (S). Currently, the chemical industry uses the stepwise preparation of this acid. First, the feedstock is oxidized to furnace gas (sulfur oxide 4), then it is oxidized to sulfur oxide (6), then hydration occurs.
In the food industry, it is used as an additive E513. Acting as an emulsifier, sulfuric acid is used in the production of beverages (regulates acidity). E513 is also an integral component of mineral fertilizers. In organic synthesis, sulfuric acid acts as a catalyst for various reactions: hydration, dehydrogenation, alkylation.
At home, H 2 SO 4 acts as an electrolyte for automotive batteries. When working with it, it is important to follow the rules of caution, since sulfuric acid is a caustic chemical.
Sulphates
Analyzing the basic chemical formulas of inorganic compounds, it is necessary to pay special attention to the salts of sulfuric acid. Magnesium sulfate, for example, has a laxative effect. It is administered as an antispasmodic to patients in case of hypertension, as well as to improve the removal of bile. MgSO 4 also has an anticonvulsant effect.
Sodium thiosulfate is an antidote to lead, cyanides, halogens, and mercury.
Together with hydrochloric acid, sodium thiosulfate is used to treat various dermatological diseases. For example, these drugs are in demand for the treatment of scabies.
Carbohydrates
As part of the school curriculum, the basic chemical formulas of organic compounds are considered. Let us dwell only on some of them. In particular, glucose has the molecular formula C 6 H 12 O 6 . This substance belongs to the class of carbohydrates (monosaccharide), it has high-quality reactions to the aldehyde group contained in the molecule: “silver mirror”, “play of colors”.
This monosaccharide is necessary for brain cells, as well as for red blood cells. In the case of a sedentary lifestyle, the need for it in a person decreases.
Organic acids
The basic formulas of chemical elements considered in the high school course give an idea of the versatility of organic chemistry. In particular, hyaluronic acid is one of the most important building materials of the extracellular space of connective tissues - the matrix - these are glycosaminoglycans, which include hyaluronic acid (hyaluronan). Thanks to this substance, tissues are provided with an anti-compression function: hyaluronan absorbs a large volume of water, becomes a gel-like substance, and prevents the swelling process.
Hyaluronic acid allows nutrients to spread freely throughout all tissues. It is part of most solutions intended for cosmetic injections. This substance helps to strengthen, smooth the skin, start the regeneration of dermal cells.
In cosmetology, hyaluronic injections are used, which nourish the cells with oxygen, increase the protective abilities of the skin, remove toxic substances, increase the plasticity of the skin, normalize the water balance.
Synthetic lactic acid
This substance is secreted in muscle tissue during prolonged physical activity. In beauty salons, synthetic lactic acid is used, which minimizes the likelihood of allergies. Preparations in which the active substance is lactic acid helps shape the cheeks, cheekbones, smooth wrinkles near the nose and lips, and get rid of deep wrinkles.
The procedure takes no more than 30 minutes. The skin is cleaned of impurities, an antiseptic is applied, injections are administered, then the beautician makes massage of the treated area. Do not use synthetic lactic acid on the forehead, lips, eyes. Such procedures are contraindicated for pregnant women, adolescents, as well as people with diseases of the circulatory system.
Characterization of glycolic acid
Glycolic acid belongs to the category of fruit or alpha-hydroxyl acids. It is found in nature in grapes, sugar beets, sugar cane. HOOC-CH 2 -OH is the simplest hydroxy acid. Colorless crystals with the smell of burnt sugar, they are well soluble in the input, alcohol, diethyl ether.
Cosmetics with glycolic acid are especially often used by adolescents when caring for the fatty type of epidermis, as it makes it possible to get rid of greasy shine, narrow pores and eliminate acne. The greater the activity of the sebaceous glands, the higher should be the concentration of this active substance in the composition of the product. Glycolic acid is suitable for dealing with small inflamed areas on the skin, exfoliation of the stratum corneum of the epidermis, including hypersensitive skin.
Settlement Tasks
The basic chemical formulas for solving problems in chemistry, which are offered to ninth-graders at the final exam in chemistry, are associated with different types of chemical reactions. We give a concrete example. It is necessary to determine the mass of sediment formed by the interaction of 100 grams of solution with a mass fraction of 10% with an excess of sodium chloride.
In order to cope with such a task, you first need to determine the mass of the substance through the proportion. Next, an equation for the reaction of interaction between sodium chloride and silver nitrate is compiled. Using the periodic system of chemical elements of D. I. Mendeleev, the molar masses of the substances are determined, then their masses, taking into account the coefficients. The last action is to solve the proportion, determine the mass of the precipitate, which is silver chloride.
Important points
The basic chemical formulas of substances and their names are questions that are included in the tasks of the exam and the exam. The children should be familiar with the terminology, be able to distinguish simple and complex compounds, determine the belonging of the compounds to one of the classes of inorganic (organic) substances.
To summarize
Currently, there are many substances that are considered as part of the school chemistry course. For example, in grades 8-9, special attention is paid to the consideration of the following classes of inorganic substances: acids, bases, oxides, salts. In high school, in the context of organic chemistry, alcohols, carboxylic acids, aldehydes, carbohydrates, fats, and various classes of hydrocarbons are analyzed.
Typical representatives of each class of organic and inorganic compounds are also found in computational problems, the types of which are studied not only in chemistry classes, but also as part of optional classes (after school hours).