What is manganese: we study a chemical element. Manganese (VII) compounds

PART 1

1. The oxidation state (s. O.) Is the conditional charge of the atoms of a chemical element in a complex substance, calculated on the basis of the assumption that it consists of simple ions.

You should know!

1) In connections with. O. hydrogen = +1, except for hydrides .
2) In connections with. O. oxygen = -2, except for peroxides and fluorides
3) The oxidation state of metals is always positive.

For metals of the main subgroups of the first three groups, p. O. constant:

Group IA metals - p. O. = +1,
Group IIA metals - p. O. = +2,
Group IIIA metals - p. O. = +3. 4

Free atoms and simple substances c. O. = 0.5

Total s. O. all elements in the compound = 0.

2. The way names are formed two-element (binary) compounds.

4. Complete the table "Names and formulas of binary compounds".

5. Determine the oxidation state of the highlighted element of the complex compound.

PART 2

1. Determine the oxidation state of chemical elements in compounds by their formulas. Write down the names of these substances.

2. Divide the substances FeO, Fe2O3, CaCl2, AlBr3, CuO, K2O, BaCl2, SO3 into two groups. Write down the names of the substances, indicating the degree of oxidation.

3. Establish a correspondence between the name and the oxidation state of the atom of a chemical element and the formula of the compound.

4. Make formulas of substances by name.

5. How many molecules are contained in 48 g of sulfur (IV) oxide?

6.Using the Internet and other sources of information, prepare a message on the use of any binary connection according to the following plan:

1) formula;
2) name;
3) properties;
4) application.

H2O water, hydrogen oxide. Water at normal conditions liquid, colorless, odorless, in a thick layer - blue. The boiling point is about 100⁰С. It is a good solvent. A water molecule consists of two hydrogen atoms and one oxygen atom; this is its qualitative and quantitative composition. This is a complex substance, it is characterized by the following chemical properties: interaction with alkali metals, alkaline earth metals.

The exchange reactions with water are called hydrolysis. These reactions are of great importance in chemistry.

7. The oxidation state of manganese in the K2MnO4 compound is:

8. The lowest oxidation state of chromium is in the compound, the formula of which is:

1) Cr2O3

9. Chlorine exhibits the maximum oxidation state in a compound, the formula of which is:

For a long time, one of the compounds of this element, namely its dioxide (known as pyrolusite), was considered a type of mineral, magnetic iron ore. Only in 1774 did one of the Swedish chemists find out that there is an unexplored metal in pyrolusite. As a result of heating this mineral with coal, the same unknown metal was obtained. At first it was called manganum, later the modern name - manganese - appeared. The chemical element has many interesting properties, which will be discussed below.

Located in a side subgroup of the seventh group of the periodic table (important: all elements of the side subgroups are metals). The electronic formula is 1s2 2s2 2p6 3s2 3p6 4s2 3d5 (typical d-element formula). Manganese as a free substance has a silvery white color. Due to its chemical activity, it occurs in nature only in the form of compounds such as oxides, phosphate and carbonate. The substance is refractory, the melting point is 1244 degrees Celsius.

Interesting! In nature, there is only one isotope of a chemical element with an atomic mass of 55. The remaining isotopes are obtained artificially, and the most stable radioactive isotope with an atomic mass of 53 (half-life is approximately the same as that of uranium).

Manganese oxidation state

It has six different oxidation states. In the zero oxidation state, the element is capable of forming complex compounds with organic ligands (for example, P (C5H5) 3), as well as inorganic ligands:

carbon monoxide (dimarganese decacarbonyl),
nitrogen,
phosphorus trifluoride,
nitric oxide.

The oxidation state +2 is typical for manganese salts. Important: these compounds have purely reducing properties. The most stable compounds with an oxidation state of +3 are Mn2O3 oxide, as well as a hydrate of this oxide Mn (OH) 3. At +4, MnO2 and amphoteric oxide-hydroxide MnO (OH) 2 are the most stable.

The oxidation state of manganese +6 is typical for permanganate acid and its salts existing only in aqueous solution. The oxidation state +7 is typical for manganic acid, its anhydride, existing only in aqueous solution, as well as salts - permanganates (analogy with perchlorates) - strong oxidants. It is interesting that when reducing potassium permanganate (in everyday life it is called potassium permanganate), three different reactions are possible:

In the presence of sulfuric acid, the MnO4- anion is reduced to Mn2 +.
If the medium is neutral, the MnO4- ion is reduced to MnO (OH) 2 or MnO2.
In the presence of alkali, the MnO4- anion is reduced to the manganate ion MnO42-.

Manganese as chemical element

Chemical properties

Under normal conditions, it is inactive. The reason is the oxide film that appears when exposed to oxygen in the air. If the metal powder is slightly heated, it burns, turning into MnO2.

When heated, it interacts with water, displacing hydrogen. As a result of the reaction, a practically insoluble nitrous oxide hydrate Mn (OH) 2 is obtained. This substance prevents further interaction with water.

Interesting! Hydrogen is soluble in manganese, and as the temperature rises, the solubility increases (a gas solution in the metal is obtained).

With very strong heating (temperatures above 1200 degrees Celsius), it interacts with nitrogen, and nitrides are obtained. These compounds can have different compositions, which is typical for the so-called berthollides. Interacts with boron, phosphorus, silicon, and in molten form - with carbon. The latter reaction proceeds during the reduction of manganese with coke.

When interacting with dilute sulfuric and hydrochloric acids, salt is obtained and hydrogen is released. But the interaction with strong sulfuric acid is different: the reaction products are salt, water and sulfur dioxide (at first, sulfuric acid is reduced to sulfurous acid; but due to instability, sulfurous acid decomposes into sulfur dioxide and water).

When reacting with dilute nitric acid, nitrate, water, and nitric oxide are obtained.

Forms six oxides:

nitrous oxide, or MnO,
oxide, or Mn2O3,
nitrous oxide Mn3O4,
dioxide, or MnO2,
permanganate anhydride MnO3,
manganese anhydride Mn2O7.

Interesting! Nitrous oxide under the influence of atmospheric oxygen gradually turns into oxide. Permanganate anhydride is not isolated.

Nitrous oxide is a compound with the so-called fractional oxidation state. When dissolved in acids, divalent manganese salts are formed (salts with the Mn3 + cation are unstable and are reduced to compounds with the Mn2 + cation).

Dioxide, oxide, nitrous oxide are the most stable oxides. Manganese anhydride is unstable. There are analogies with other chemical elements:

Mn2O3 and Mn3O4 are basic oxides, and are similar in properties to analogous iron compounds;
MnO2 - amphoteric oxide, similar in properties to aluminum and trivalent chromium oxides;
Mn2O7 - acid oxide, its properties are very similar to the highest chlorine oxide.

It is easy to see the analogy with chlorates and perchlorates. Manganates, like chlorates, are obtained indirectly. But permanganates can be obtained both directly, that is, by the interaction of anhydride and metal oxide / hydroxide in the presence of water, and indirectly.

In analytical chemistry, the Mn2 + cation fell into the fifth analytical group. There are several reactions that can detect this cation:

When interacting with ammonium sulfide, a precipitate of MnS precipitates, its color is flesh; when mineral acids are added, the precipitate dissolves.
When reacted with alkalis, a white precipitate of Mn (OH) 2 is obtained; however, when interacting with atmospheric oxygen, the color of the precipitate changes from white to brown - Mn (OH) 3 is obtained.
If hydrogen peroxide and an alkali solution are added to the salts with the Mn2 + cation, a dark brown precipitate of MnO (OH) 2 precipitates.
When adding an oxidizing agent (lead dioxide, sodium bismuthate) to salts with Mn2 + cation and strong solution nitric acid, the solution turns crimson, which means that Mn2 + has oxidized to HMnO4.

Chemical properties

Manganese valencies

The element is in the seventh group. Typical manganese - II, III, IV, VI, VII.

Zero valence is typical for a free substance. Divalent compounds - salts with Mn2 + cation, trivalent - oxide and hydroxide, tetravalent - dioxide, as well as oxide-hydroxide. Heptavalent and hexavalent compounds are salts with the anions MnO42- and MnO4-.

How to get and from what get manganese? From manganese and iron-manganese ores, as well as from salt solutions. There are three different ways obtaining manganese:

recovery with coke,
alumothermy,
electrolysis.

In the first case, coke is used as a reducing agent, as well as carbon monoxide. The metal is recovered from the ore, where there is an admixture of iron oxides. The result is both ferromanganese (an alloy with iron) and carbide (what is carbide is a combination of a metal with carbon).

For more pure substance one of the methods of metallothermy is used - alumothermy. First, pyrolusite is calcined to produce Mn2O3. Then the resulting oxide is mixed with aluminum powder. During the reaction, a lot of heat is released, as a result, the resulting metal melts, and aluminum oxide covers it with a slag "cap".

Manganese is a metal of medium activity and is in the Beketov series to the left of hydrogen and to the right of aluminum. This means that during the electrolysis of aqueous solutions of salts with the Mn2 + cation, the metal cation is reduced at the cathode (during the electrolysis of a very dilute solution, water is also reduced at the cathode). During electrolysis aqueous solution MnCl2, the following reactions take place:

MnCl2 Mn2 + + 2Cl-

Cathode (negatively charged electrode): Mn2 + + 2e Mn0

Anode (positively charged electrode): 2Cl- - 2e 2Cl0 Cl2

The final reaction equation:

MnCl2 (e-s) Mn + Cl2

Electrolysis produces the purest metallic manganese.

Useful video: manganese and its compounds

Application

Manganese is widely used. Both the metal itself and its various compounds are used. It is used in free form in metallurgy for various purposes:

as a "deoxidizer" in steel melting (oxygen is bound and Mn2O3 is formed);
as an alloying element: a strong steel with high wear resistance and impact resistance is obtained;
for smelting the so-called armored steel grade;
as a component of bronze and brass;
to create manganin, an alloy with copper and nickel. Various electrical devices are made from this alloy, for example, rheostats.

For the manufacture of Zn-Mn electrochemical cells, MnO2 is used. MnTe and MnAs are used in electrical engineering.

Manganese use

Potassium permanganate, often called potassium permanganate, is widely used both in everyday life (for medicinal baths) and in industry and laboratories. The crimson color of permanganate becomes discolored when unsaturated hydrocarbons with double and triple bonds are passed through the solution. On strong heating, permanganates decompose. This produces manganates, MnO2, and oxygen. This is one of the ways to obtain chemically pure oxygen in the laboratory.

It is possible to obtain salts of permanganate acid only indirectly. For this, MnO2 is mixed with solid alkali and heated in the presence of oxygen. Another way to obtain solid manganates is to calcine permanganates.

Manganate solutions have a beautiful dark green color. However, these solutions are unstable and undergo a disproportionation reaction: the dark green color changes to crimson, and a brown precipitate also falls out. The reaction produces permanganate and MnO2.

Manganese dioxide is used in the laboratory as a catalyst in the decomposition of potassium chlorate (berthollet's salt), as well as for the production of pure chlorine. Interestingly, as a result of the interaction of MnO2 with hydrogen chloride, an intermediate product is obtained - an extremely unstable compound MnCl4, which decomposes into MnCl2 and chlorine. Neutral or acidified solutions of salts with the Mn2 + cation have a pale pink color (Mn2 + forms a complex with 6 water molecules).

Useful video: manganese is an element of life

Output

Such is a brief description of manganese and its chemical properties. It is a silvery-white metal of medium activity, interacts with water only when heated, and, depending on the oxidation state, exhibits both metallic and non-metallic properties. Its compounds are used in industry, in everyday life and in laboratories to obtain pure oxygen and chlorine.

Manganese is one of the most important metals for metallurgy. In addition, he is generally quite an unusual element, with which they are associated Interesting Facts... Important for living organisms, required in the production of many alloys, chemical substances... Manganese - a photo of which can be seen below. It is its properties and characteristics that we will consider in this article.

Characteristics of a chemical element

If we talk about manganese as an element, then first of all it is necessary to characterize its position in it.

It is located in the fourth large period, seventh group, side subgroup.
The serial number is 25. Manganese is a chemical element, the atoms of which are +25. The number of electrons is the same, neutrons - 30.
Meaning atomic mass - 54,938.
The designation of the chemical element manganese is Mn.
The Latin name is manganese.

It is located between chromium and iron, which explains its similarity with them in physical and chemical characteristics.

Manganese - chemical element: transition metal

If we consider the electronic configuration of the reduced atom, then its formula will have the form: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5. It becomes obvious that the element under consideration is from the d-family. Five electrons on the 3d sublevel indicate the stability of the atom, which is manifested in its chemical properties.

As a metal, manganese is a reducing agent, however, most of its compounds are capable of exhibiting rather strong oxidizing abilities. It's connected with varying degrees oxidation and valencies possessed by this element. This is the peculiarity of all metals in this family.

Thus, manganese is a chemical element located among other atoms and having its own special characteristics. Let's consider what these properties are in more detail.

Manganese is a chemical element. Oxidation state

We have already given the electronic formula of the atom. According to her, this element is capable of showing several positive degrees oxidation. It:

The valency of the atom is IV. The most stable are those compounds in which the values of +2, +4, +6 appear in manganese. The highest oxidation state allows the compounds to act as the strongest oxidizing agents. For example: KMnO 4, Mn 2 O 7.

Compounds with +2 are reducing agents, manganese (II) hydroxide has amphoteric properties, with a predominance of basic ones. Intermediate oxidation states form amphoteric compounds.

Discovery history

Manganese is a chemical element that was not discovered immediately, but gradually and by different scientists. However, people have used its compounds since ancient times. Manganese (IV) oxide was used to melt glass. One Italian stated that the addition of this compound in the chemical production of glasses dyes their color purple. Along with this, the same substance helps to eliminate turbidity in colored glasses.

Later in Austria, the scientist Kaym managed to obtain a piece of metallic manganese by applying high temperature to pyrolysite (manganese (IV) oxide), potash and coal. However, this sample had many impurities, which he could not eliminate, so the discovery did not take place.

Still later, another scientist also synthesized a mixture, in which a significant proportion was pure metal. It was Bergman, who had previously discovered the element nickel. However, he was not destined to complete the matter.

Manganese is a chemical element, which Karl Scheele was first able to obtain and isolate in the form of a simple substance in 1774. However, he did it together with I. Gan, who completed the process of smelting a piece of metal. But even they failed to completely rid it of impurities and get 100% product yield.

Nevertheless, it was this time that became the discovery of this atom. The same scientists attempted to give the name, as the discoverers. They chose the term manganesium. However, after the discovery of magnesium, confusion began, and the name of manganese was changed to the modern one (H. David, 1908).

Since manganese is a chemical element, the properties of which are very valuable for many metallurgical processes, over time, it became necessary to find a way to obtain it in the purest possible form. This problem was solved by scientists from all over the world, but managed to be resolved only in 1919 thanks to the works of R. Agladze, a Soviet chemist. It was he who found a way to obtain pure metal with a substance content of 99.98% from manganese sulfates and chlorides by electrolysis. Now this method is used all over the world.

Being in nature

Manganese is a chemical element, a photo of a simple substance of which can be seen below. In nature, there are a lot of isotopes of this atom, the number of neutrons in which fluctuates strongly. Thus, the mass numbers vary from 44 to 69. However, the only stable isotope is an element with a value of 55 Mn, all the rest have either a negligibly short half-life, or exist in too small quantities.

Since manganese is a chemical element, the oxidation state of which is very different, it also forms many compounds in nature. In its pure form, this element does not occur at all. In minerals and ores, its constant neighbor is iron. In total, several of the most important rocks can be identified, which include manganese.

Pyrolusite. Compound formula: MnO 2 * nH 2 O.
Psilomelan, MnO2 * mMnO * nH2O molecule.
Manganite, formula MnO * OH.
Brownite is less common than the rest. Formula Mn 2 O 3.
Gausmanite, formula Mn * Mn 2 O 4.
Rhodonite Mn 2 (SiO 3) 2.
Manganese carbonate ores.
Raspberry spar or rhodochrosite - MnCO 3.
Purpurite - Mn 3 PO 4.

In addition, several more minerals can be designated, which also include the element in question. It:

calcite;
siderite;
clay minerals;
chalcedony;
opal;
sandy-silty compounds.

In addition to rocks and sedimentary rocks, minerals, manganese is a chemical element that is part of the following objects:

Plant organisms. The largest accumulators of this element are: water nut, duckweed, diatoms.
Rusty mushrooms.
Some types of bacteria.
The following animals: red ants, crustaceans, molluscs.
Humans - The daily requirement is approximately 3-5 mg.
The waters of the World Ocean contain 0.3% of this element.
The total content in the earth's crust is 0.1% by weight.

In general, it is the 14th most common element of all on our planet. Among heavy metals, it is the second after iron.

Physical properties

From the point of view of the properties of manganese as a simple substance, several main physical characteristics for him.

In the form of a simple substance, it is a fairly hard metal (on the Mohs scale, the indicator is 4). Color - silvery-white, in air it is covered with a protective oxide film, shines on the cut.
The melting point is 1246 0 С.
Boiling - 2061 0 C.
It has good conductive properties and is paramagnetic.
The density of the metal is 7.44 g / cm 3.
It exists in the form of four polymorphic modifications (α, β, γ, σ), differing in the structure and shape of the crystal lattice and in the packing density of atoms. Their melting point also differs.

In metallurgy, three main forms of manganese are used: β, γ, σ. Alpha is less common, as it is too fragile in its properties.

Chemical properties

From the point of view of chemistry, manganese is a chemical element, the ionic charge of which varies greatly from +2 to +7. This leaves its mark on his activity. In free form in air, manganese reacts very weakly with water and dissolves in dilute acids. However, as soon as the temperature is increased, the activity of the metal rises sharply.

So, he is able to interact with:

nitrogen;
carbon;
halogens;
silicon;
phosphorus;
gray and other non-metals.

When heated without air access, the metal easily turns into a vaporous state. Depending on the oxidation state that manganese exhibits, its compounds can be both reducing and oxidizing agents. Some exhibit amphoteric properties. So, the main ones are typical for compounds in which it is +2. Amphoteric - +4, and acidic and strong oxidative in the highest value +7.

Despite the fact that manganese is a transition metal, complex compounds for it are few. This is due to sustainable electronic configuration atom, because its 3d-sublevel contains 5 electrons.

Methods of obtaining

There are three main ways in which manganese (chemical element) is obtained in industry. As the name reads in Latin, we have already designated - manganum. If you translate it into Russian, it will be "yes, I really do clarify, discolor." Manganese owes this name to the manifested properties known since antiquity.

However, despite the fame, they managed to get it in its pure form for use only in 1919. This is done by the following methods.

Electrolysis, the product yield is 99.98%. In this way, manganese is obtained in the chemical industry.
Silicothermal, or reduction with silicon. At this method fusion of silicon and manganese (IV) oxide occurs, as a result of which a pure metal is formed. The yield is about 68%, since the compound of manganese with silicon to form silicide is a side process. This method used in the metallurgical industry.
Aluminothermic method - recovery with aluminum. Also does not give too high a product yield, manganese is formed contaminated with impurities.

The production of this metal is essential for many processes in metallurgy. Even a small addition of manganese can greatly affect the properties of alloys. It has been proven that many metals dissolve in it, filling its crystal lattice.

For the extraction and production of this element, Russia ranks first in the world. Also, this process is carried out in countries such as:

China.
Kazakhstan.
Georgia.
Ukraine.

Industrial use

Manganese is a chemical element, the use of which is important not only in metallurgy. but also in other areas. In addition to pure metal, various compounds of a given atom are also of great importance. Let's designate the main ones.

There are several types of alloys that, thanks to manganese, have unique properties... So, for example, it is so strong and wear-resistant that it is used for smelting parts of excavators, stone processing machines, crushers, ball mills, and armor parts.
Manganese dioxide is an indispensable oxidizing element of electroplating; it is used to create depolarizers.
Many manganese compounds are needed for the organic synthesis of various substances.
Potassium permanganate (or potassium permanganate) is used in medicine as a strong disinfectant.
This element is part of bronze, brass, forms its own alloy with copper, which is used for the manufacture of aircraft turbines, blades and other parts.

Biological role

The daily requirement for manganese for humans is 3-5 mg. Deficiency of this element leads to oppression nervous system, sleep disturbance and anxiety, dizziness. Its role has not yet been fully studied, but it is clear that, first of all, it influences:

height;
activity of the sex glands;
the work of hormones;
blood formation.

This element is present in all plants, animals, humans, which proves its important biological role.

Manganese is a chemical element, interesting facts about which can impress any person, and also make them understand how important it is. Here are the most basic ones that have found their imprint in the history of this metal.

In hard times civil war in the USSR, one of the first export products was ore containing large amounts of manganese.
If manganese dioxide is fused with nitrate and then the product is dissolved in water, then amazing transformations will begin. First, the solution will be colored in green color, then the color will change to blue, then purple. Finally, it will turn crimson and gradually brown precipitate will fall out. If the mixture is shaken, then the green color will be restored again and everything will happen again. It is for this that potassium permanganate got its name, which translates as "mineral chameleon".
If fertilizers containing manganese are applied to the soil, then the productivity of plants will increase and the rate of photosynthesis will increase. Winter wheat will form better grains.
The largest block of manganese mineral rhodonite weighed 47 tons and was found in the Urals.
There is a ternary alloy called manganin. It is composed of elements such as copper, manganese and nickel. Its uniqueness is that it has great electrical resistance, which does not depend on temperature, but is influenced by pressure.

Of course, this is not all that can be said about this metal. Manganese is a chemical element, interesting facts about which are quite diverse. Especially if we talk about the properties that it gives to various alloys.

The highest oxidation state of manganese +7 corresponds to acidic oxide Mn2O7, manganese acid HMnO4 and its salts - permanganates.

Manganese (VII) compounds - strong oxidizing agents... Mn2O7 is a greenish-brown oily liquid, on contact with which alcohols and ethers ignite. Manganese acid HMnO4 corresponds to Mn (VII) oxide. It exists only in solutions, but it is considered one of the strongest (α - 100%). The maximum possible concentration of HMnO4 in solution is 20%. Salts HMnO4 - permanganates - the strongest oxidizing agents; in aqueous solutions, like the acid itself, they have a raspberry color.

In redox reactions permanganates are strong oxidizing agents. Depending on the reaction of the medium, they are reduced either to salts of divalent manganese (in an acidic medium), manganese (IV) oxide (in neutral) or manganese (VI) compounds - manganates - (in alkaline). Obviously, in an acidic environment, the oxidizing ability of Mn + 7 is most pronounced.

2KMnO4 + 5Na2SO3 + 3H2SO4 → 2MnSO4 + 5Na2SO4 + K2SO4 + 3H2O

2KMnO4 + 3Na2SO3 + H2O → 2MnO2 + 3Na2SO4 + 2KOH

2KMnO4 + Na2SO3 + 2KOH → 2K2MnO4 + Na2SO4 + H2O

Permanganates in both acidic and alkaline media oxidize organic matter:

2KMnO4 + 3H2SO4 + 5C2H5OH → 2MnSO4 + K2SO4 + 5CH3COH + 8H2O

alcohol aldehyde

4KMnO4 + 2NaOH + C2H5OH → MnO2 ↓ + 3CH3COH + 2K2MnO4 +

When heated, potassium permanganate decomposes (this reaction is used to obtain oxygen in laboratory conditions):

2KMnO4 K2MnO4 + MnO2 + O2

Thus, for manganese, the same dependences are characteristic: when passing from inferior oxidation to higher acidic properties of oxygen compounds increase, and in OM reactions, the reducing properties are replaced by oxidizing ones.

For the body, permanganates are poisonous due to their strong oxidizing properties.

In case of poisoning with permanganates, hydrogen peroxide in an acetic acid medium is used as an antidote:

2KMnO4 + 5H2O2 + 6CH3COOH → 2 (CH3COO) 2Mn + 2CH3COOK + 5O2 + 8H2O

The KMnO4 solution is a cauterizing and bactericidal agent for treating the surface of the skin and mucous membranes. The strong oxidizing properties of KMnO4 in an acidic medium underlie the analytical method of permanganatometry used in clinical analysis to determine the oxidizability of water, uric acid in urine.

The human body contains about 12 mg of Mn in various compounds, with 43% concentrated in bone tissue. It affects blood formation, bone formation, growth, reproduction and some other body functions.

manganese (II) hydroxide possesses weakly basic properties, is oxidized by atmospheric oxygen and other oxidizing agents to permanganate acid or its salts manganites:

Мn (ОН) 2 + Н2О2 → Н2МnО3 ↓ + Н2О permanganous acid

(brown sediment) B alkaline environmentМn2 + is oxidized to МnО42-, and in acidic to МnО4-:

МnSO4 + 2КNО3 + 4КОН → К2МnО4 + 2КNО2 + К2SO4 + 2Н2О

Salts of manganese H2MnO4 and manganese HMnO4 acids are formed.

If in the experiment Mn2 + exhibits reducing properties, then the reducing properties of Mn2 + are weakly expressed. In biological processes, it does not change the oxidation state. Stable biocomplexes Mn2 + stabilize this oxidation state. The stabilizing effect appears in the long retention time of the hydration shell. Manganese (IV) oxide MnO2 is a stable natural manganese compound that occurs in four modifications. All modifications are amphoteric and have redox duality. Examples of redox duality МnО2: МnО2 + 2КI + 3СО2 + Н2О → I2 + МnСО3 + 2КНСО3

6МnО2 + 2NH3 → 3Мn2О3 + N2 + 3Н2О

4МnО2 + 3О2 + 4КОН → 4КМnО4 + 2Н2О

Mn (VI) compounds- unstable. In solutions, they can turn into compounds Mn (II), Mn (IV) and Mn (VII): manganese oxide (VI) MnO3 is a dark red mass that causes a cough. The hydrated form of МnО3 is a weak permanganous acid Н2МnO4, which exists only in aqueous solution. Its salts (manganates) are easily destroyed by hydrolysis and heating. At 50 ° С МnО3 decomposes:

2МnО3 → 2МnО2 + О2 and hydrolyzes when dissolved in water: 3МnО3 + Н2О → МnО2 + 2НМnО4

Derivatives of Mn (VII) are manganese (VII) oxide Mn2O7 and its hydrated form - acid HMnO4, known only in solution. Мn2О7 is stable up to 10 ° С, decomposes with an explosion: Мn2О7 → 2МnО2 + О3

When dissolved in cold water acid Мn2O7 + Н2О → 2НМnО4 is formed

Salts of manganic acid НМnО4- permanganates. Ions are responsible for the violet color of solutions. Form crystal hydrates of the type EMnO4 ∙ nH2O, where n = 3-6, E = Li, Na, Mg, Ca, Sr.

Permanganate KMnO4 is readily soluble in water ... Permanganates - strong oxidants. This property is used in medical practice for disinfection, in pharmacopoeial analysis for the identification of H2O2 by interaction with KMnO2 in an acidic medium.

Permanganates are poisons for the body., their neutralization can occur as follows: 2КМnO4 + 5Н2O2 + 6СН3СООН = 2Мn (СН3СОО) 2 + 2СН3СООК + 8Н2О + 5O2

For the treatment of acute poisoning with permanganate a 3% aqueous solution of H2O2 acidified with acetic acid is used. Potassium permanganate oxidizes organic matter of tissue cells and microbes. In this case, KMnO4 is reduced to MnO2. Manganese (IV) oxide can also interact with proteins to form a brown complex.

Under the action of potassium permanganate KMnO4, proteins are oxidized and coagulated. Based on this its application as an external preparation with antimicrobial and cauterizing properties. Moreover, its effect is manifested only on the surface of the skin and mucous membranes. Oxidizing properties of an aqueous solution of KMnO4 use for neutralization of toxic organic substances. Oxidation produces less toxic products. For example, the drug morphine is converted into a biologically inactive oxymorphine. Potassium permanganate apply in titrimetric analysis to determine the content of various reducing agents (permanganatometry).

High oxidizing capacity of permanganate use in ecology to assess pollution Wastewater(permanganate method). The amount of oxidized (discolored) permanganate is used to determine the content of organic impurities in water.

Permanganate method (permanganatometry) is used also in clinical laboratories to determine the content of uric acid in the blood.

Permanganic acid salts are called permanganates. The most famous salt is potassium permanganate KMnO4 - dark purple crystalline substance, sparingly soluble in water. KMnO4 solutions have a dark crimson color, and at high concentrations - violet, characteristic of MnO4-

Permanganate potassium decomposes when heated

2KMnO4 = K2MnO4 + MnO2 + O2

Potassium permanganate is a very strong oxidizing agent, easily oxidizes many inorganic and organic substances. The degree of manganese reduction is highly dependent on the pH of the medium.

Recovery e potassium permanganate in environments of different acidity proceeds in accordance with the scheme:

Acid pH<7

manganese (II) (Mn2 +)

KMnO4 + reducing agent Neutral pH = 7

manganese (IV) (MnO2)

Alkaline pH> 7

manganese (VI) (MnO42-)

Mn2 + decolorization of KMnO4 solution

MnO2 brown sediment

MnO42 - the solution turns green

Examples of reactions with the participation of potassium permanganate in various media (acidic, neutral and alkaline).

NS<7 5K2SO3 + 2KMnO4 + 3H2SO4 = 2МnSO4 + 6K2SO4 + 3Н2O

MnO4 - + 8H ++ 5℮ → Mn2 ++ 4H2O 5 2

SO32- + H2O - 2ē → SO42- + 2H + 2 5

2MnO4 - + 16H ++ 5SO32- + 5H2O → 2Mn2 ++ 8H2O + 5SO42- + 10H +

2MnO4 - + 6H ++ 5SO32- → 2Mn2 ++ 3H2O + 5SO42-

pH = 7 3K2SO3 + 2KMnO4 + H2O = 2МnO2 + 3K2SO4 + 2KOH

MnO4- + 2H2О + 3ē = MnO2 + 4OH- 3 2

SO32- + H2O - 2ē → SO42- + 2H + - 2 3

2MnO4 - + 4H2O + 3SO32- + 3H2O → 2MnO2 + 8OH- + 3SO42- + 6H + 6H2O + 2OH-

2MnO4 - + 3SO32- + H2O → 2MnO2 + 2OH- + 3SO42

pH> 7 K2SO3 + 2KMnO4 + 2KOH = 2K2MnO4 + K2SO4 + H2O

MnO4- +1 ē → MnO42- 1 2

SO32- + 2ОH- - 2ē → SO42- + H2О 2 1

2MnO4- + SO32- + 2OH- → 2MnO42- + SO42- + H2O

Potassium permanganate KMnO4 is used in medical practice as a disinfectant and antiseptic for washing wounds, rinsing, douching, etc. Light pink solution of KMnO4 is used internally in case of poisoning for gastric lavage.

Potassium permanganate is widely used as an oxidizing agent.

With the help of KMnO4, many drugs are analyzed (for example, the percentage concentration (%) of an H2O2 solution).

general characteristics d-elements of VIIIB subgroup. The structure of atoms. Elements of the iron family. Oxidation states in compounds. Physical and chemical properties of iron. Application. The prevalence and forms of finding d-elements of the iron family in nature. Iron salts (II, III). Complex compounds of iron (II) and iron (III).

General properties elements of VIIIB subgroup:

1) The general electronic formula of the last levels is (n - 1) d (6-8) ns2.

2) In each period, this group contains 3 elements that form triads (families):

a) Iron family: iron, cobalt, nickel.

b) The family of light platinum metals (palladium family): ruthenium, rhodium, palladium.

c) The family of heavy platinum metals (platinum family): osmium, iridium, platinum.

3) The similarity of elements in each family is explained by the closeness of atomic radii, therefore the density within the family is also close.

4) Density increases with increasing period number (atomic volumes are small).

5) These are metals with high temperatures melting and boiling.

6) Maximum oxidation state at individual elements grows with the period number (for osmium and ruthenium it reaches 8+).

7) These metals are able to include hydrogen atoms in the crystal lattice, in their presence atomic hydrogen appears - an active reducing agent. Therefore, these metals are catalysts for the addition of a hydrogen atom.

8) The compounds of these metals are colored.

9) Characteristic oxidation states for iron +2, +3, in unstable compounds +6. Nickel has +2, unstable +3. Platinum has +2, unstable +4.

Iron. Getting iron(all these reactions take place when heated)

* 4FeS2 + 11O2 = 2Fe2O3 + 8SO2. Prerequisite: annealing of iron pyrite.

* Fe2O3 + 3H2 = 2Fe + 3H2O. * Fe2O3 + 3CO = 2Fe + 3CO2.

* FeO + C = Fe + CO.

* Fe2O3 + 2Al = 2Fe + Al2O3 (thermite method). Condition: heating.

* = Fe + 5CO (decomposition of iron pentacarbonyl is used to obtain very pure iron).

Iron chemical properties Reactions with simple substances

* Fe + S = FeS. Condition: heating. * 2Fe + 3Cl2 = 2FeCl3.

* Fe + I2 = FeI2 (iodine is a less strong oxidizing agent than chlorine; FeI3 does not exist).

* 3Fe + 2O2 = Fe3O4 (FeO Fe2O3 is the most stable iron oxide). In humid air Fe2O3 nH2O is formed.

The electronic configuration of the unexcited manganese atom is 3d 5 4s 2; the excited state is expressed by the electronic formula 3d 5 4s 1 4p 1.

The oxidation states +2, +4, +6, +7 are most typical for manganese in compounds.

Manganese is a silvery-white, brittle, quite active metal: in the series of voltages, it is located between aluminum and zinc. Manganese is covered in air oxide film protecting it from further oxidation. In a finely divided state, manganese is easily oxidized.

Manganese (II) oxide MnO and the corresponding hydroxide Mn (OH) 2 have basic properties - when they interact with acids, divalent manganese salts are formed: Mn (OH) 2 + 2 H + ® Mn 2+ + 2 H 2 O.

Mn 2+ cations are also formed upon dissolution of metallic manganese in acids. Manganese (II) compounds exhibit reducing properties, for example, the white precipitate of Mn (OH) 2 darkens rapidly in air, gradually oxidizing to MnO 2: 2 Mn (OH) 2 + O 2 ® 2 MnO 2 + 2 H 2 O.

Manganese (IV) oxide MnO 2 is the most stable manganese compound; it is easily formed both during the oxidation of manganese compounds in a lower oxidation state (+2), and during the reduction of manganese compounds in higher oxidation states (+6, +7):

Mn (OH) 2 + H 2 O 2 ® MnO 2 + 2 H 2 O;

2 KMnO 4 + 3 Na 2 SO 3 + H 2 O ® 2 MnO 2 ¯ + 3 Na 2 SO 4 + 2 KOH.

MnO 2 is an amphoteric oxide, however, it is acidic, and its basic properties are poorly expressed. One of the reasons that MnO 2 does not show clearly expressed basic properties is its strong oxidative activity in an acidic medium (= +1.23 V): MnO 2 is reduced to Mn 2+ ions, and does not form stable salts of tetravalent manganese. The hydrated form corresponding to manganese (IV) oxide should be considered as hydrated manganese dioxide MnO 2 × xH 2 O. Manganese (IV) oxide as an amphoteric oxide formally corresponds to ortho- and meta-forms of permanganous acid not isolated in the free state: H 4 MnO 4 - ortho-form and H 2 MnO 3 - meta-form. Known manganese oxide Mn 3 O 4, which can be considered as a salt of divalent manganese of the ortho-form of permanganous acid Mn 2 MnO 4 - manganese (II) orthomanganite. There are reports in the literature on the existence of oxide Mn 2 O 3. The existence of this oxide can be explained by considering it as a salt of divalent manganese of the meta-form of permanganate acid: MnMnO 3 - manganese (II) metamanganite.

When manganese dioxide is fused with oxidants such as chlorate or potassium nitrate in an alkaline medium, tetravalent manganese is oxidized to a hexavalent state, and potassium manganate is formed, a salt that is very unstable even in a solution of permanganous acid H 2 MnO 4, the anhydride of which (MnO 3) is unknown:

MnO 2 + KNO 3 + 2 KOH ® K 2 MnO 4 + KNO 2 + H 2 O.

Manganates are unstable and prone to disproportionate reversible reaction: 3 K 2 MnO 4 + 2 H 2 O ⇆ 2 KMnO 4 + MnO 2 ¯ + 4 KOH,

as a result, the green color of the solution, caused by the manganate ions MnO 4 2–, changes to a violet color, which is characteristic of the permanganate ions MnO 4 -.

The most widely used compound of heptavalent manganese is potassium permanganate KMnO 4 - a salt known only in a solution of manganic acid HMnO 4. Potassium permanganate can be obtained by oxidizing manganates with strong oxidants, for example, chlorine:

2 K 2 MnO 4 + Cl 2 ® 2 KMnO 4 + 2 KCl.

Manganese oxide (VII), or manganese anhydride, Mn 2 O 7 is an explosive green-brown liquid. Mn 2 O 7 can be obtained by the reaction:

2 KMnO 4 + 2 H 2 SO 4 (conc.) ® Mn 2 O 7 + 2 KHSO 4 + H 2 O.

Manganese compounds in the highest degree oxidation +7, in particular permanganates, are strong oxidizing agents. The depth of reduction of permanganate ions and their oxidative activity depends on the pH of the medium.

In a strongly acidic environment, the product of the reduction of permanganates is the Mn 2+ ion, and bivalent manganese salts are obtained:

MnO 4 - + 8 H + + 5 e - ® Mn 2+ + 4 H 2 O (= +1.51 V).

In a neutral, slightly alkaline or slightly acidic medium, as a result of the reduction of permanganate ions, MnO 2 is formed:

MnO 4 - + 2 H 2 O + 3 e - ® MnO 2 ¯ + 4 OH - (= +0.60 V).

MnO 4 - + 4 H + + 3 e - ® MnO 2 ¯ + 2 H 2 O (= +1.69 V).

In a strongly alkaline medium, permanganate ions are reduced to manganate ions MnO 4 2–, and salts of the type K 2 MnO 4, Na 2 MnO 4 are formed:

MnO 4 - + e - ® MnO 4 2– (= +0.56 V).