Reasons for the diversity of chemical compounds. Variety of organic and inorganic substances. Allotropic modifications of oxygen
2014-06-04Causes of a wide variety of substances. Thanks to the existence of more than 100 types of atoms and their ability to combine with each other in different quantities and sequences, millions of substances were formed. Among them are substances of natural origin. These are water, oxygen, oil, starch, sucrose and many others.
Thanks to advances in chemistry, it has become possible to create new substances even with predetermined properties. Such substances are also known to you. This is polyethylene, the vast majority of medicines, artificial rubber - the main substance in the composition of rubber, from which bicycle and car tires are made. Since there are a lot of substances, there was a need to somehow divide them into separate groups.
Substances are divided into two groups - simple and complex.
simple substances. There are substances in the formation of which atoms of only one type, that is, one chemical element, participate. Let's use the reference table. 4 (see p. 39) and consider examples. From the atoms of the chemical element aluminum given in it, a simple substance aluminum is formed. This substance contains only aluminum atoms. Like aluminum, the simple substance iron is formed only from the atoms of one chemical element - iron. Please note that the names of substances are usually written with a lowercase letter, and chemical elements - with a capital letter.
Substances formed by atoms of only one chemical element are called simple.
Oxygen is also a simple substance. However, this simple substance differs from aluminum and iron in that the oxygen atoms from which it is formed are connected two in one molecule. The main substance in the composition of the Sun is hydrogen. This is a simple substance, the molecules of which consist of two hydrogen atoms.
Simple substances are composed of either atoms or molecules. Molecules of simple substances formed from two or more atoms of one chemical element.
Complex substances. There are hundreds of simple substances, while there are millions of complex ones. They are made up of atoms of various elements. Indeed, the molecule of the complex substance of water contains hydrogen and oxygen atoms. Methane is made up of hydrogen and carbon atoms. Note that the molecules of both substances contain hydrogen atoms. A water molecule has one oxygen atom, but a methane molecule has one carbon atom.
Such a small difference in the composition of molecules and such a big difference in properties! Methane is a flammable substance, water does not burn and is used to extinguish fires.
The subsequent division of substances into groups is the division into organic and inorganic substances.
organic substances. The name of this group of substances comes from the word organism and refers to complex substances that were first obtained from organisms.
Today, more than 10 million organic substances are known, and not all of them are of natural origin. Examples of organic substances are proteins, fats, carbohydrates, which are rich in food (Fig. 20).
Many organic substances were created by man in laboratories. But the very name "organic matter" has been preserved. Now it extends to almost all complex substances containing carbon atoms.
Organic substances are complex substances whose molecules contain carbon atoms.
inorganic substances. The remaining complex substances that are not related to organic are called inorganic substances. All simple substances are inorganic. Inorganic substances are carbon dioxide, baking soda and some others.
In the bodies of inanimate nature, inorganic substances predominate, in the bodies of living nature, most substances are organic. On fig. 21 depicts bodies of inanimate nature and man-made bodies. They are formed either from inorganic substances (Fig. 21, a-d), or made from organic substances of natural origin artificially created by man (Fig. 21, d-f).
One sucrose molecule consists of 12 carbon atoms, 22 hydrogen atoms, 11 oxygen atoms. The composition of its molecule is denoted by the notation C12H22O11. When burned, charring) sucrose turns black. This is because the sucrose molecule decomposes into a simple substance carbon (it has a black color) and a complex substance water.
Be a conservationist
Organic materials (polyethylene) are used to make a variety of packaging materials, such as lawn water bottles, bags, and disposable tableware. They are strong, light, but not subject to destruction in nature, and therefore pollute the environment. Especially harmful is the burning of these products, since during their combustion toxic substances are formed.
Protect nature from such pollution - throw them into the fire of plastic products, collect them in specially designated places. Advise your relatives and friends to use biopackages, Bioware, which decompose over time without harming nature.
Reasons for the diversity of chemicals
Currently, the reasons for the diversity of chemicals are usually explained by two phenomena - isomerism and allotropy.
Substances that have the same composition, but different chemical or spatial structure, and therefore different properties, are called isomers.
Main types isomerism :
Structural isomerism, in which substances differ in the order of bonding of atoms in molecules:isomerism carbon skeleton
isomerism positions of multiple bonds:
deputies
isomerism positions of functional groups
ALLOTROPY, the existence of chemical elements in two or more molecular or crystalline forms. For example, allotropes are ordinary oxygen O2 and ozone O3; in this case, allotropy is due to the formation of molecules with different numbers of atoms. Most often, allotropy is associated with the formation of crystals of various modifications. Carbon exists in two distinct crystalline allotropic forms: diamond and graphite. Previously, it was believed that the so-called. amorphous forms of carbon, charcoal and soot, are also its allotropic modifications, but it turned out that they have the same crystalline structure as graphite. Sulfur occurs in two crystalline modifications: rhombic (a-S) and monoclinic (b-S); at least three of its non-crystalline forms are known: l-S, m-S and violet. For phosphorus, white and red modifications have been well studied; black phosphorus has also been described; at temperatures below -77 ° C, there is another kind of white phosphorus. Allotropic modifications of As, Sn, Sb, Se, and at high temperatures - of iron and many other elements have been found.
Enantiotropic and monotropic forms. Crystalline modifications of a chemical element can transform one into another in different ways, which can be illustrated by the examples of sulfur and phosphorus. At ordinary temperature, the orthorhombic modification of sulfur is stable, which, when heated to 95.6 ° C and a pressure of 1 atm, passes into a monoclinic form. The latter, when cooled below 95.6 ° C, again turns into a rhombic form. Thus, the transition of one form of sulfur to another occurs at the same temperature, and the forms themselves are called enantiotropic. Another picture is observed for phosphorus. Its white form can turn red at almost any temperature. At temperatures below 200°C, the process is very slow, but it can be accelerated with a catalyst such as iodine. The reverse transition of red phosphorus to white is impossible without the formation of an intermediate gas phase. The red form is stable over the entire temperature range where it is in the solid state, while the white form is unstable at any temperature (metastable). The transition from an unstable form to a stable one is, in principle, possible at any temperature, but the reverse is not; there is no defined transition point. Here we are dealing with monotropic modifications of an element. Two known modifications of tin are enantiotropic. Modifications of carbon - graphite and diamond - are monotropic, and the form of graphite is stable. The red and white forms of phosphorus are monotropic, and its two white modifications are enantiotropic, the transition temperature is -77 ° C at a pressure of 1 atm.
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The purpose of the lesson:
consider the composition, structure of substances and identify the reasons for their diversity.
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Substances (by structure) molecular, or daltonides (have a constant composition, except for polymers) non-molecular, or berthollides (have a variable composition) atomic ionic metal H2, P4, NH3, CH4, CH3COOH P, SiO2 Cu, Fe NaCl, KOH
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The law of constancy of the composition of substances
Joseph Louis Proust (1754-1826) was a French chemist and analyst. The study of the composition of various substances, carried out by him in 1799-1803, served as the basis for the discovery of the law of composition constancy for substances of a molecular structure. Each chemically pure substance, regardless of location and method of preparation, has a constant composition and properties.
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What does the molecular formula of CH4 show?
The substance is complex, consists of two chemical elements (C, H). Each molecule contains 1 C atom, 4 H atoms. Substance of molecular structure, CPS. Mr= ω(C) = ω(H) = m(C):m(H) = 12: 16= 0.75=75% 12+1 4=16 1-0.75=0.25=25% 12:4 =3:1
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What are the reasons for the diversity of substances?
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At the beginning of the 20th century, a scandalous story occurred in a warehouse of military equipment in St. Petersburg: during an audit, to the horror of the quartermaster, it turned out that the tin buttons for soldiers' uniforms had disappeared, and the boxes in which they were stored were filled to the brim with gray powder. And although it was bitterly cold in the warehouse, the unfortunate quartermaster became hot. Still: he, of course, will be suspected of theft, and this promises nothing but hard labor. The poor fellow was saved by the conclusion of the chemical laboratory, where the auditors sent the contents of the boxes: “The substance you sent for analysis is undoubtedly tin. Obviously, in this case, a phenomenon known in chemistry under the name "tin plague" took place. ?
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"Tin Plague"
White tin is stable at t0 >130С Gray tin is stable at t0
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Allotropy is the ability of atoms of one chemical element to form several simple substances. Allotropic modifications are simple substances formed by atoms of the same chemical element.
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Allotropic modifications of oxygen
O2 - oxygen is a colorless gas; has no smell; poorly soluble in water; boiling point -182.9 C. O3 - ozone ("smelling") gas of a pale purple color; has a pungent odor; dissolves 10 times better than oxygen; boiling point -111.9 C; the most bactericidal.
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Allotropic modifications of carbon
Graphite Diamond Soft Has a gray color Low metallic luster Electrically conductive Leaves a mark on paper. Hard Colorless Cuts glass Refracts light Dielectric
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Fullerene Carbin Graphene Harder and stronger than diamond, but stretches a quarter of its length like rubber. Graphene does not pass gases and liquids, conducts heat and electricity better than copper. Fine-grained black powder (density 1.9-2 g/cm³), semiconductor.
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Rhombic sulfur is a type of octahedron with cut corners. Light yellow powder. Monoclinic sulfur - in the form of needle-like crystals of yellow color. Plastic sulfur is a rubbery mass of dark yellow color. Can be obtained in the form of threads.
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Allotropic modifications of phosphorus
P (red phosphorus) (white phosphorus) P4 Odorless, does not glow in the dark, is not poisonous! Has a garlic smell, glows in the dark, poisonous!
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C4H8
Before you is a painting by an unknown artist. The one who offers the most isomers will be able to buy it. Starting price - 2 isomers.
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CH2 \u003d CH - CH2 - CH3 CH2 \u003d C - CH3 Butene-1CH3 2-methylpropene-1 (methylpropene) Butene-2 CH3 CH \u003d CH-CH3 C \u003d C C \u003d C CH3 CH3 CH3 CH3 H H H H H Cis - butene - 2 Trans - butene - 2 H2C CH2 H2C CH2 Cyclobutane H2C CH CH3 CH2 methylcyclopropane
2Preparation of alcohols from saturated and unsaturated hydrocarbons. Industrial synthesis of methanol.
3. Experiment. Realization of transformations: salt - insoluble base - metal oxide.
Sulfuric acid reacts with copper(II) oxide when heated. Cu 2+ ions pass into the solution and give it a blue color.
CuO + H 2 SO 4 \u003d СuSO 4 (copper sulfate salt) + H 2 O,
CuO + 2H + = Сu 2+ + H 2 O.
An alkali solution is added to the filtrate, a blue precipitate is observed:
CuSO 4 + 2NaOH \u003d Cu (OH) 2 (insoluble copper oxide) + Na 2 SO 4,
Cu 2+ + 2OH - \u003d Cu (OH) 2.
when the blue precipitate of copper (II) hydroxide is heated, a black substance is formed - this is copper (II) oxide and water:
Cu(OH)2 = CuO + H2O
1. Higher oxygen-containing chemical elements of the third period, their composition and comparative characteristics of properties.
Phosphorus forms a number of oxygen-containing acids (oxoacids). Some of them are monomeric. for example, phosphinic, phosphorous, and phosphoric(V) (orthophosphoric) acids. Phosphorus acids can be monobasic (single-protonic) or polybasic (multi-protonic). In addition, phosphorus also forms polymeric oxoacids. Such acids may have an acyclic or a cyclic structure. For example, diphosphoric(V) (pyrophosphoric) acid is a dimeric phosphorus oxoacid.
The most important of all these acids is phosphoric(V) acid (its other name is orthophosphoric acid). Under normal conditions, it is a white crystalline substance that deliquesces when it absorbs moisture from the air. Its 85% aqueous solution is called "phosphoric acid syrup". Phosphorous(V) acid is a weak tribasic acid:
Chlorine forms several oxygen-containing acids. The higher the oxidation state of chlorine in these acids, the higher their thermal stability and acid strength:
HOCl< НСlO2 < НСlO3 < НClO4
HClO3 and HClO4 are strong acids, and HClO4 is one of the strongest among all known acids. The remaining two acids only partially dissociate in water and exist in aqueous solution predominantly in molecular form. Among the oxygen-containing acids of chlorine, only HclO4 can be isolated in free form. Other acids exist only in solution.
The oxidizing ability of oxygen-containing acids of chlorine decreases with an increase in its oxidation state:
HOCl and HClO2 are particularly good oxidizers. For example, an acidic solution of HOCl:
1) oxidizes iron (II) ions to iron (III) ions:
2) decomposes in sunlight to form oxygen:
3) when heated to approximately 75 ° C, it disproportionates into chloride ions and chlorate (V) ions:
The remaining higher acid-containing acids of the elements of the third period (H3AlO3, H2SiO3) are weaker than phosphoric acid. Sulfuric acid (H2SO4) is less strong than perchloric (VII) acid, but stronger than phosphoric acid. In general, with an increase in the oxidation state of an element that forms an acid, the strength of the acid itself increases:
H3AlO3< H2SiO3 < H3PO4 < H2SO4 < НСlO4
2. General characteristics of macromolecular compounds: composition, structure, reactions underlying their production (for example, polyethylene or synthetic rubber).
3. 3 a da cha. Calculation of the mass of the starting substance, if the practical yield of the product is known and its mass fraction (in percent) of the theoretically possible yield is indicated.
Task. Determine the mass of magnesium carbonate reacted with hydrochloric acid if 8.96 liters of carbon monoxide (IV) were obtained, which is 80% of the theoretically possible yield.
Ticket number 25.
General methods for obtaining metals. The practical significance of electrolysis on the example of salts of anoxic acids.
Metals are found in nature mainly in the form of compounds. Only metals with low chemical activity (noble metals) are found in nature in a free state (platinum metals, gold, copper, silver, mercury). Of the structural metals, only iron, aluminum, and magnesium are found in nature in the form of compounds in sufficient quantities. They form powerful deposits of deposits of relatively rich ores. This makes it easier to harvest them on a large scale.
Since the metals in the compounds are in an oxidized state (have a positive oxidation state), getting them in a free state is reduced to a reduction process:
This process can be carried out chemically or electrochemically.
In chemical reduction, coal or carbon monoxide (II), as well as hydrogen, active metals, and silicon are most often used as a reducing agent. With the help of carbon monoxide (II), iron is obtained (in the blast furnace process), many non-ferrous metals (tin, lead, zinc, etc.):
Hydrogen reduction is used, for example, to produce tungsten from tungsten(VI) oxide:
The use of hydrogen as a reducing agent ensures the highest purity of the resulting metal. Hydrogen is used to produce very pure iron, copper, nickel and other metals.
The method of obtaining metals, in which metals are used as a reducing agent, is called metallothermic. In this method, active metals are used as a reducing agent. Examples of metallothermic reactions:
aluminothermy:
magnesiumthermy:
Metal-thermal experiments for obtaining metals were first carried out by the Russian scientist N. N. Beketov in the 19th century.
Metals are most often obtained by the reduction of their oxides, which in turn are isolated from the corresponding natural ore. If the original ore is sulfide minerals, then the latter are subjected to oxidative roasting, for example:
Electrochemical production of metals is carried out during the electrolysis of melts of the corresponding compounds. In this way, the most active metals, alkali and alkaline earth metals, aluminum, and magnesium are obtained.
Electrochemical reduction is also used for refining(purification) of "raw" metals (copper, nickel, zinc, etc.) obtained by other methods. In electrolytic refining, a “rough” (with impurities) metal is used as an anode, and a solution of compounds of this metal is used as an electrolyte.
Methods for obtaining metals, carried out at high temperatures, are called pyrometallurgical(in Greek pyr - fire). Many of these methods have been known since ancient times. At the turn of the XIX-XX centuries. begin to develop hydrometallurgical methods of obtaining metals (in Greek hydor-water). With these methods, the ore components are transferred into an aqueous solution and then the metal is isolated by electrolytic or chemical reduction. So get, for example, copper. Copper ore containing copper (II) oxide CuO is treated with dilute sulfuric acid:
To reduce copper, the resulting solution of copper (II) sulfate is either subjected to electrolysis, or the solution is treated with iron powder.
The hydrometallurgical method has a great future, as it makes it possible to obtain a product without extracting the ore from the ground.
2. Types of synthetic rubbers, their properties and applications.
3. Experience. Obtaining the named gaseous substance and carrying out reactions that characterize its properties; (carbon dioxide)
CO2 is a typical acidic oxide: it reacts with alkalis (for example, causes lime water to become cloudy), with basic oxides and with water.
Carbon dioxide is obtained by acting on salts of carbonic acid - carbonates with solutions of hydrochloric, nitric and even acetic acids. In the laboratory, carbon dioxide is produced by the action of hydrochloric acid on chalk or marble:
CaCO3 + 2HCl = CaCl2 + H20 + CO2 it's carbon dioxide
In industry, large amounts of carbon dioxide are obtained by burning limestone:
CaCO3 = CaO + CO2
Chemical reactions with carbon dioxide
When carbon monoxide (IV) is dissolved in water, carbonic acid H2CO3 is formed, which is very unstable and easily decomposes into its original components - carbon dioxide and water:
CO2 + H20 -> H2CO3
It does not burn and does not support combustion (Fig. 44) and therefore is used to extinguish fires. However, magnesium continues to burn in carbon dioxide to form oxide and release carbon as soot.
Bodies in which atoms and molecules are arranged in the correct geometric order. All crystalline substances have their own, strictly defined melting point. bodies in which atoms and molecules are arranged randomly. When heated, they do not have a specific temperature corresponding to the transition of the solid phase to the liquid. Crystalline Amorphous Solids
Amorphous substances Amorphous bodies can be considered as strongly cooled liquids with a very high viscosity coefficient. They have weakly expressed properties of fluidity. The particles are completely random and are at a close distance to each other. Amorphous bodies do not have a thermal effect. Amorphous substances, having a large supply of free energy, are chemically more active than crystalline substances of the same composition. The strength of amorphous substances is lower than the strength of crystalline ones.
The use of amorphous substances - is carried out in the field of medicine (a substance of an amorphous structure is an excellent biomaterial for implantation in bones. The resulting special screws, plates, pins, pins are introduced in severe fractures) - carried out in the field of industry (glass production) - used as jewelry (pearls , amber, opal) - used in the food industry (sugar candy, chewing gum)
Spatial isomers (stereoisomers) with the same composition and the same chemical structure differ in the spatial arrangement of atoms in the molecule. Optical - molecules of optical isomers are incompatible in space. Geometric, or cis-and-trans-characteristic of substances containing double bonds or cyclic.
Allotropic modifications of oxygen Oxygen Colorless gas; Has no smell; Poorly soluble in water; Boiling point 182.9 C Ozone Pale violet gas; Has a pungent odor; It dissolves 10 times better than oxygen; Boiling point -111.9 C.
