Manganese hydride. Volatile hydrogen compounds Other binary compounds
Detailed investigations in the temperature range from 20 to 1300° were carried out by Sieverts and Moritz on manganese distillate, and also by Potter and Lukens on electrolytic distilled manganese. In both cases, at different temperatures, the pressure of hydrogen was measured, which was in equilibrium with the preliminarily completely degassed metal.
Very similar results were obtained in both works. On fig. 79 shows the data of Sieverts and Moritz on the volume of hydrogen adsorbed by 100 g of manganese in the temperature range from 20 to 1300° during heating and cooling of two samples of pure manganese.
The solubility of hydrogen in the α-modification of manganese first decreases and then increases with increasing temperature. The solubility of hydrogen in β-manganese is noticeably higher than in α-manganese; therefore, the β→α-conversion is accompanied by a noticeable increase in hydrogen adsorption. Solubility in β-manganese increases with temperature.
The β→γ transformation is also accompanied by an increase in hydrogen solubility, which in γ-manganese, as well as in β-manganese, increases with temperature. The transformation is accompanied by a decrease in solubility. The solubility of hydrogen in δ-manganese increases to the melting point, and the solubility of hydrogen in liquid manganese is noticeably higher than its solubility in any of the modifications of manganese in the solid state.
Thus, the change in the solubility of hydrogen in various allotropic modifications of manganese makes it possible to develop a simple and elegant method for studying the temperatures of allotropic transformations, as well as their hysteresis at different heating and cooling rates.
The results of Potter and Lukens, in general, are very close to the results of Sieverts and Moritz, as can be seen from the data in Table. 47. The convergence of the results is very good, except for the change in solubility in the α-phase in the temperature range from room temperature to 500 °: Sieverts and Moritz found that the solubility is much higher than follows from the data of Potter and Lukens. The reason for this discrepancy is unclear.
Potter and Lukens found that at a constant temperature, the solubility of hydrogen (V) changes with pressure (P) according to the dependence:
where K is a constant.
No researcher has found any manganese hydrides.
Hydrogen content in electrolytic manganese. Since hydrogen is deposited on the cathode during electrical deposition, it is not surprising that the metal thus obtained must contain hydrogen.
The hydrogen content of electrolytic manganese and issues related to its removal were studied by Potter, Hayes and Lukens. We studied ordinary electrolytic manganese of industrial purity, which was previously kept for three months at room temperature.
Measurements of the liberated (released) volume of hydrogen were made at temperatures up to 1300°; the results are shown in fig. 80.
When heated to 200°, very little gas is released, but already at 300° a very significant volume is released. A little more is released at 400°, but on subsequent heating the amount of hydrogen liberated changes slightly, except in cases where the solubility changes due to allotropic transformations of manganese.
It has been found that manganese contains approximately 250 cm3 of hydrogen per 100 g of metal. When heated to 400° for 1 hour in air at normal pressure, 97% of the amount that can be removed is removed. As expected, as the external pressure decreases, a shorter heating time is required to remove the same amount of hydrogen.
The hydrogen present in manganese is believed to form a supersaturated interstitial solid solution. The effect of hydrogen on the lattice parameters of α-manganese was studied by Potter and Guber; a certain expansion (increase) of the lattice is observed (Table 48), which is 0.0003% at 1 cm3 of hydrogen per 100 g of metal.
Heating to remove hydrogen causes compression (reduction) of the lattice (Table 49).
Accurate measurements of the lattice parameters on samples with a high hydrogen content are very difficult, since a blurred diffraction pattern is obtained. Potter and Huber attribute this to the inhomogeneous distribution of gas in the metal. This fuzziness does not increase with increasing hydrogen content and even decreases somewhat at higher hydrogen contents. It has been established that electrolytic manganese cannot be obtained with a hydrogen content of more than 615 cm3 per 100 g, which corresponds to two hydrogen atoms per unit cell of α-manganese. With a uniform distribution of hydrogen in a metal, one can expect an equal degree of distortion of elementary gratings, and the diffraction pattern should contain clear lines.
Manganese(II) oxide- MnO - lower manganese oxide, monoxide.
basic oxide. Let's not dissolve in water. Easily oxidized to form a brittle MnO 2 shell. It is reduced to manganese when heated with hydrogen or active metals.
Manganese(II) oxide can be obtained by calcining at a temperature of 300 °C oxygen-containing salts of manganese(II) in an inert gas atmosphere. From common MnO 2 it is obtained through partial reduction at temperatures of 700-900 ° C with hydrogen or carbon monoxide.
Manganese(II) hydroxide- inorganic compound, manganese metal hydroxide with the formula Mn(OH) 2 , light pink crystals, insoluble in water. Shows weak basic properties. Oxidizes in air.
Manganese (II) hydroxide is formed by the interaction of its salts with alkalis:
Chemical properties.
Manganese (II) hydroxide is easily oxidized in air to brown manganese oxohydroxide, which further decomposes into manganese (IV) oxide:
· Manganese (II) hydroxide has basic properties. It reacts with acids and acid oxides:
· Manganese (II) hydroxide has reducing properties. In the presence of strong oxidizing agents, it can oxidize to permanganate:
Manganese(III) oxide- inorganic compound, manganese metal oxide with the formula Mn 2 O 3, brown-black crystals, insoluble in water.
Receipt.
· In nature, there are minerals brownite, kurnakite and bixbyite - manganese oxide with various impurities.
Oxidation of manganese(II) oxide:
Recovery of manganese(IV) oxide:
Chemical properties.
Decomposes on heating:
When dissolved in acids, it disproportionates:
When fused with metal oxides, it forms salts of manganites:
Does not dissolve in water.
Manganese(III) hydroxide –Mn2O3ּ H 2 O or MnO(OH) occurs naturally as a mineral manganite(brown manganese ore). Artificially obtained manganese (III) hydroxide is used as a black-brown paint.
When interacting with acidic oxidizing agents, it forms manganese salts.
Salts of manganese (II), as a rule, are well soluble in water, except for Mn 3 (PO 4) 2, MnS, MnCO 3.
manganese sulfate(II) MnSO 4 is a white salt, one of the most stable compounds of manganese (II). In the form of crystalline MnSO 4 7H 2 O occurs in nature. It is used for dyeing fabrics, and also, along with manganese (II) chloride MnCl 2 - to obtain other manganese compounds.
manganese carbonate(II) MnCO 3 is found in nature as manganese powder and is used in metallurgy.
manganese nitrate(II) Mn(NO 3) 2 is obtained only artificially and is used to separate rare earth metals.
Salts of manganese are catalysts for oxidative processes involving oxygen. They are used in desiccants. Linseed oil with the addition of such a desiccant is called drying oil.
Manganese(IV) oxide (manganese dioxide) MnO 2 - dark brown powder, insoluble in water. The most stable compound of manganese, widely distributed in the earth's crust (mineral pyrolusite).
Chemical properties.
Under normal conditions, it behaves rather inertly. When heated with acids, it exhibits oxidizing properties, for example, it oxidizes concentrated hydrochloric acid to chlorine:
With sulfuric and nitric acids, MnO 2 decomposes with the release of oxygen:
When interacting with strong oxidizing agents, manganese dioxide is oxidized to compounds Mn 7+ and Mn 6+:
Manganese dioxide exhibits amphoteric properties. So, when a sulfuric acid solution of the MnSO 4 salt is oxidized with potassium permanganate in the presence of sulfuric acid, a black precipitate of the Mn(SO 4) 2 salt is formed.
And when fused with alkalis and basic oxides, MnO 2 acts as an acid oxide, forming salts - manganites:
It is a catalyst for the decomposition of hydrogen peroxide:
Receipt.
Under laboratory conditions, it is obtained by thermal decomposition of potassium permanganate:
It can also be obtained by the reaction of potassium permanganate with hydrogen peroxide. In practice, the formed MnO 2 catalytically decomposes hydrogen peroxide, as a result of which the reaction does not proceed to the end.
At temperatures above 100 °C by reduction of potassium permanganate with hydrogen:
64. Manganese (VI) compounds, methods of preparation and properties. Manganese oxide (VII), permanganic acid and permanganates - obtaining, properties, application.
Manganese(VI) oxide- an inorganic compound, manganese metal oxide with the formula MnO 3, a dark red amorphous substance, reacts with water.
It is formed during the condensation of violet vapors released when a solution of potassium permanganate in sulfuric acid is heated:
Chemical properties.
Decomposes on heating:
Reacts with water:
Forms salts with alkalis - manganates:
Manganese(VI) hydroxide exhibits an acidic character. free manganese (VI) acid is unstable and disproportionates in an aqueous solution according to the scheme:
3H 2 MnO 4(c) → 2HMnO 4(c) + MnO 2(t) + 2H 2 O (l).
Manganates (VI) are formed by fusing manganese dioxide with alkali in the presence of oxidizing agents and have an emerald green color. Manganates (VI) are rather stable in strongly alkaline medium. When alkaline solutions are diluted, hydrolysis occurs, accompanied by disproportionation:
3K 2 MnO 4 (c) + 2H 2 O (l) → 2KMnO 4 (c) + MnO 2 (t) + 4KOH (c).
Manganates (VI) are strong oxidizing agents that are reduced in an acidic environment to Mn(II), and in neutral and alkaline environments - up to MNO2. Under the action of strong oxidizing agents, manganates (VI) can be oxidized to Mn(VII):
2K 2 MnO 4 (c) + Cl 2 (d) → 2KMnO 4 (c) + 2KCl (c).
When heated above 500 ° C, manganate (VI) decomposes into products:
manganate (IV) and oxygen:
2K 2 MnO 4 (t) → K 2 MnO 3 (t) + O 2 (g).
Manganese(VII) oxide Mn 2 O 7- greenish-brown oily liquid (t pl \u003d 5.9 ° C), unstable at room temperature; a strong oxidizing agent, in contact with combustible substances, ignites them, possibly with an explosion. Explodes from a push, from a bright flash of light, when interacting with organic substances. Manganese (VII) oxide Mn 2 O 7 can be obtained by the action of concentrated sulfuric acid on potassium permanganate:
The resulting manganese(VII) oxide is unstable and decomposes into manganese(IV) oxide and oxygen:
At the same time, ozone is released:
Manganese(VII) oxide reacts with water to form permanganic acid, which has a purple-red color:
It was not possible to obtain anhydrous permanganic acid; it is stable in solution up to a concentration of 20%. This very strong acid, the apparent degree of dissociation in a solution with a concentration of 0.1 mol / dm 3 is 93%.
Permanganic acid – strong oxidizing agent . More energetic interaction Mn2O7 combustible substances ignite when in contact with it.
Salts of permanganic acid are called permanganates . The most important of these is potassium permanganate, which is a very strong oxidizing agent. Its oxidizing properties with respect to organic and inorganic substances are often encountered in chemical practice.
The degree of reduction of permanganate ion depends on the nature of the medium:
1) acidic environment Mn(II) (salts Mn 2+)
MnO 4 - + 8H + + 5ē \u003d Mn 2+ + 4H 2 O, E 0 \u003d +1.51 B
2) neutral environment Mn(IV) (manganese(IV) oxide)
MnO 4 - + 2H 2 O + 3ē \u003d MnO 2 + 4OH -, E 0 \u003d +1.23 B
3) alkaline environment Mn (VI) (manganates M 2 MnO 4)
MnO 4 - +ē \u003d MnO 4 2-, E 0 \u003d + 0.56B
As can be seen, the strongest oxidizing properties of permanganates are exhibited by in an acidic environment.
The formation of manganates occurs in a highly alkaline solution, which suppresses hydrolysis K2MnO4. Since the reaction usually takes place in sufficiently dilute solutions, the end product of the reduction of permanganate in an alkaline medium, as well as in a neutral one, is MnO 2 (see disproportionation).
At a temperature of about 250 ° C, potassium permanganate decomposes according to the scheme:
2KMnO 4(t) K 2 MnO 4(t) + MnO 2(t) + O 2(g)
Potassium permanganate is used as an antiseptic. Aqueous solutions of its various concentrations from 0.01 to 0.5% are used for wound disinfection, gargling and other anti-inflammatory procedures. Successfully 2 - 5% solutions of potassium permanganate are used for skin burns (the skin dries up, and the bubble does not form). For living organisms, permanganates are poisons (cause proteins to coagulate). Their neutralization is carried out with a 3% solution H 2 O 2, acidified with acetic acid:
2KMnO 4 + 5H 2 O 2 + 6CH 3 COOH → 2Mn (CH 3 COO) 2 + 2CH 3 COOK + 8H 2 O + 5O 2
65. Rhenium compounds (II), (III), (VI). Rhenium (VII) compounds: oxide, rhenium acid, perrhenates.
Rhenium(II) oxide- inorganic compound, rhenium metal oxide with the formula ReO, black crystals, insoluble in water, forms hydrates.
Rhenium oxide hydrate ReO H 2 O is formed by the reduction of rhenium acid with cadmium in an acidic medium:
Rhenium(III) oxide- inorganic compound, rhenium metal oxide with the formula Re 2 O 3 , black powder, insoluble in water, forms hydrates.
Obtained by hydrolysis of rhenium(III) chloride in an alkaline medium:
Easily oxidized in water:
Rhenium(VI) oxide- inorganic compound, rhenium metal oxide with the formula ReO 3 , dark red crystals, insoluble in water.
Receipt.
· Proportionation of rhenium(VII) oxide:
Recovery of rhenium(VII) oxide with carbon monoxide:
Chemical properties.
Decomposes on heating:
Oxidized by concentrated nitric acid:
Forms rhenites and perrhenates with alkali metal hydroxides:
Oxidized by atmospheric oxygen:
Recovered with hydrogen:
Rhenium(VII) oxide- inorganic compound, rhenium metal oxide with the formula Re 2 O 7 , light yellow hygroscopic crystals, soluble in cold water, reacts with hot water.
Receipt.
Oxidation of metallic rhenium:
Decomposition on heating of rhenium(IV) oxide:
Rhenium(IV) oxide oxidation:
Decomposition upon heating of rhenium acid:
Chemical properties.
Decomposes on heating:
· Reacts with hot water:
Reacts with alkalis to form perrhenates:
It is an oxidizing agent:
Recovered with hydrogen:
In proportion to rhenium:
Reacts with carbon monoxide:
Rhenic acid- an inorganic compound, an oxygen-containing acid with the formula HReO 4 , exists only in aqueous solutions, forms salts perrhenates.
The transfer of rhenium from poorly soluble compounds, such as ReO and ReS2, into solution is carried out by acid decomposition or alkaline fusion with the formation of soluble perrhenates or rhenium acid. Conversely, the extraction of rhenium from solutions is carried out by its precipitation in the form of slightly soluble perrhenates of potassium, cesium, thallium, etc. Ammonium perrhenate is of great industrial importance, from which metallic rhenium is obtained by reduction with hydrogen.
Rhenic acid is obtained by dissolving Re2O7 in water:
Re2O7 + H2O = 2HReO4.
Solutions of rhenium acid were also obtained by dissolving metallic rhenium in hydrogen peroxide, bromine water, and nitric acid. Excess peroxide is removed by boiling. Rhenic acid is obtained by oxidation of lower oxides and sulfides, from perrhenates using ion exchange and electrodialysis. For convenience, Table 2 shows the density values of rhenium acid solutions.
Rhenic acid is stable. Unlike perchloric and permanganic acids, it has very weak oxidizing properties. Recovery is usually slow. Metal amalgams and chemical agents are used as reducing agents.
Perrhenates are less soluble and thermally more stable than the corresponding perchlorates and permanganates.
Thallium, cesium, rubidium and potassium perrhenates have the lowest solubility.
Perrhenates Tl, Rb, Cs, K, Ag are poorly soluble substances, perrhenates ,Ba, Pb (II) have an average solubility, perrhenates Mg, Ca, Cu, Zn, Cd, etc. dissolve very well in water. In the composition of potassium and ammonium perrhenates, rhenium is isolated from industrial solutions.
Potassium perrhenate KReO4 - small colorless hexagonal crystals. It melts without decomposition at 555°, at higher temperatures it volatilizes, partially dissociating. The solubility of the salt in an aqueous solution of rhenium acid is higher than in water, while in the presence of H2SO4 it remains virtually unchanged.
Ammonium perrhenate NH4ReO4 is obtained by neutralizing rhenium acid with ammonia. Relatively well soluble in water. Upon crystallization from solutions, it forms continuous solid solutions with KReO4. When heated in air, it decomposes starting at 200°C, giving sublimation containing Re2O7 and a black residue of ReO2. When decomposed in an inert atmosphere, only rhenium (IV) oxide is formed according to the reaction:
2NH4ReO4 = 2ReO2 + N2 + 4H2O.
When a salt is reduced with hydrogen, a metal is obtained.
Of the salts of rhenium acid with organic bases, we note nitrone perrhenate C20H17N4ReO4, which has a very low solubility in acetate solutions, especially in the presence of an excess of nitrone acetate. The formation of this salt is used to quantify rhenium.
binary connections.
"Bi" means two. Binary compounds consist of two CE atoms.
Oxides.
Binary compounds consisting of two chemical elements, one of which oxygen in the oxidation state - 2 ("minus" two) are called oxides.
Oxides are a very common type of compound found in the earth's crust and throughout the universe.
The names of oxides are formed according to the scheme:
The name of the oxide = "oxide" + the name of the element in the genitive case + (the degree of oxidation is a Roman numeral), if variable, if constant, then do not set.
Examples of oxides. Some have trivial (historical) title.
1. H 2 O - hydrogen oxide water
CO 2 - carbon monoxide (IV) carbon dioxide (carbon dioxide)
CO - carbon monoxide (II) carbon monoxide (carbon monoxide)
Na 2 O - sodium oxide
Al 2 O 3 - aluminum oxide alumina
CuO - copper(II) oxide
FeO - iron(II) oxide
Fe 2 O 3 - iron oxide (III) hematite (red iron ore)
Cl 2 O 7 - chlorine oxide (VII)
Cl 2 O 5 - chlorine oxide (V)
Cl 2 O- chlorine(I) oxide
SO 2 - sulfur oxide (IV) sulfur dioxide
SO 3 - sulfur oxide (VI)
CaO - calcium oxide quicklime
SiO 2 - silicon oxide sand (silica)
MnO - manganese(II) oxide
N2O- nitric oxide (I) "laughing gas"
NO- nitric oxide (II)
N2O3- nitric oxide (III)
NO2- nitric oxide (IV) "fox tail"
N2O5- nitric oxide (V)
The indices in the formula are placed taking into account the degree of oxidation of CE:
Write down the oxides, arrange the oxidation states of ChE. Know how to write by name oxide formula.
Other binary compounds.
Volatile hydrogen compounds.
At the bottom of the PS there is a horizontal line "Volatile hydrogen compounds".
The formulas are listed there: RH4 RH3 RH2 RH
Each formula belongs to its own group.
For example, write the formula of the volatile hydrogen compound N (nitrogen).
We find it in the PS and see which formula is written under the V group.
It's RH3. We substitute the element nitrogen for R, it turns out ammonia NH3.
Since up to "8" nitrogen needs 3 electrons, it draws them from three hydrogens, the oxidation state of nitrogen is -3, and hydrogen has +
SiH4 - silane colorless gas with an unpleasant odor
PH3 - phosphine poisonous gas with the smell of rotten fish
AsH 3 - arsine poisonous gas with a garlic smell
H2S - hydrogen sulfide poisonous gas with the smell of rotten eggs
HCl - hydrogen chloride a gas with a pungent odor that smokes in the air; its solution in water is called hydrochloric acid. In small concentrations found in gastric juice.
NH3 ammonia a gas with a pungent irritating odour.
Its solution in water is called ammonia.
metal hydrides.
Houses: paragraph 19, ex. 3.4 writing. Formulas, how they are formed, the names of binary compounds from the abstract to know.
IN 1. Establish a correspondence between the formula of a substance and the value of the oxidation state of sulfur in it:
FORMULA OF THE SUBSTANCE OXIDATION DEGREE
A) NaHSO3 1) -2
B) SO3 2) -1
B) MgS 3) 0
D) CaSO3 4) +4 5) +6
IN 2. Establish a correspondence between the name of the substance and the type of bond between the atoms in it: NAME OF THE SUBSTANCE TYPE OF COMMUNICATION
A) calcium fluoride 1) covalent non-polar
B) silver 2) covalent polar
C) carbon monoxide (IV) 3) ionic
D) chlorine 4) metal
AT 3. Establish a correspondence between the electronic configuration of the external energy level of the atoms of a chemical element and the formula of its volatile hydrogen compound:
ELECTRONIC FORMULA FORMULA OF A VOLATILE HYDROGEN COMPOUND
A) ns2np2 1) HR
B) ns2np3 2) RH3
B) ns2np4 3) H2R
D) ns2np5 4) RH4
C1. What mass of precipitate is formed when 448 liters of carbon dioxide (N.O.) are passed through an excess of calcium hydroxide solution?
1) EO3
2) E2O7
3) E2O3
4)EO2
2. Valency of arsenic in a volatile hydrogen compound:
1) II
2) III
3)V
4) I
3. The most pronounced metallic properties are expressed in the element:
1) II group, secondary subgroup, 5 periods.
2) II group, main subgroup, 2 periods
2) Group I, main subgroup, 2 periods
4) Group I, main subgroup, 3 periods.
4. A series in which the elements are arranged in ascending order of electronegativity is:
1) AS,N,P
2) P,Si.Al
3) Te, Sc, S
4) F, Cl, Br
hydrogen compound and hydroxide. What properties (basic, acidic or amphoteric) do they have? Make up its graphical formula and determine the valence possibilities of an atom of this chemical element
Please help me paint the element, according to the plan :) Sr1) the name of the chemical element, its symbol
2) Relative atomic mass (round to the nearest whole number)
3) serial number
4) the charge of the nucleus of an atom
5) the number of protons and neutrons in the nucleus of an atom
6) total number of electrons
7) the number of the period in which the element is located
8) group number and subgroup (main and secondary) in which the element is located
9) diagram of the structure of the atom (distribution of electrons over electronic layers)
10) electronic configuration of an atom
11) chemical properties of a simple substance (metal or non-metal), comparison of the nature of properties with neighbors by subgroup and period
12) maximum oxidation state
13) the formula of the higher oxide and its nature (acidic, amphoteric, basic), characteristic reactions
14) the formula of the higher hydroxide and its nature (acidic, amphoteric, basic), characteristic reactions
15) minimum oxidation state
16) the formula of a volatile hydrogen compound
2. Three particles: Ne0, Na+ u F- - have the same:
A) the number of protons;
B) the number of neutrons;
B) mass number;
D) the number of electrons.
3. The ion has the largest radius:
4. From the following electronic formulas, select the one that corresponds to the d-element of the 4th period: a) ..3s23p64s23d5;
B)..3s23p64s2;
C) ... 3s23p64s23d104s2;
D)..3s23p64s23d104p65s24d1.
5. The electronic formula of the atom is 5s24d105p3. The formula for its hydrogen compound is:
6. From the following electronic formulas, select the one that corresponds to the element that forms the highest oxide of the composition R2O7:
B)..3s23p64s23d5;
D)..4s23d104p2.
7. A number of elements, arranged in order of strengthening non-metallic properties:
A) Mg, Si, Al;
8. The most similar physical and chemical properties are simple substances formed by chemical elements:
9. The nature of oxides in the series P2O5 - SiO2 - Al2O3 - MgO changes:
A) from basic to acidic;
B) from acidic to basic;
C) from basic to amphoteric;
D) from amphoteric to acidic.
10. The nature of higher hydroxides formed by elements of the main subgroup of group 2 changes with increasing serial number:
A) from acidic to amphoteric;
B) from basic to acidic;
C) from amphoteric to basic;
D) from acidic to basic.
The most important compounds of manganese are derivatives of two-, four- and seven-valent manganese. Of the monovalent manganese derivatives, only cyanosalts M 5 are known (where M is an alkali metal cation). These salts are obtained by electrochemical reduction of the Mn(II) cyanide complex or by sodium amalgam. In liquid ammonia, further reduction of the Mn(I) cyanide complex is possible, leading to the formation of the M 6 compound, where manganese has a zero valence. Mn(I) complexes were obtained by the interaction of Mn(CO) 5 SCN with neutral ligands - amines, phosphines, arsines.
Mn(II) salts are pink in color and are mostly highly soluble in water, especially chloride, nitrate, sulfate, acetate, and thiocyanate. Of the poorly soluble compounds, sulfide, phosphate and carbonate should be mentioned. In neutral or slightly acidic aqueous solutions, Mn(P) forms a complex ion [Mn(H 2 0) in] 2 +, and in more acidic solutions - [Mn (H 2 0) 4 ] 2+. Mn(III) salts are intensely colored and highly prone to the formation of complex compounds. They are unstable and easily hydrolyzed. Mn(IV) compounds are unstable. Only a few examples of stable Mn(IV) compounds can be cited, including Mn02, MnF 4 and Mn(SO 4) 2 . In acidic solutions, the Mn(IV) ion is reduced, while in the presence of strong oxidizing agents, it is oxidized to the permanganate ion. Of the derivatives of Mn(V), only salts are known - hypomanganates of some of the most active metals - Li, Na, K, Sr and Ba. Na 3 Mn0 4 is obtained by keeping a mixture of Mn0 2 and NaOH (1: 3) at 800 ° C in an oxygen atmosphere or by reacting Mn 2 0 3 with NaOH in an oxygen stream. Anhydrous salt has a dark green color, crystalline Na 3 Mn0 4 * 7H 2 0 is blue, and Na 3 Mn0 4 * 10H 2 0 is sky blue. The LiMn0 3 salt is insoluble in water, while the NaMn0 3 and KMn0 3 salts are highly soluble, but partially hydrolyzed.
In the solid state, alkali metal manganates(VI) are known, which form dark green, almost black crystals. Potassium manganate K 2 Mn0 4 crystallizes without water, and for sodium manganate, crystalline hydrates with 4, 6, 10 water molecules are known. Alkali metal manganates readily dissolve in dilute alkali solutions, such solutions are colored green. Pure water and weak acids decompose them according to the reaction:
3MnO 4 2- + 4H + ↔ 2 MnO 4 - + Mn0 2 + 2H 2 0.
Apparently, this process is due to the fact that free permanganous acid H 2 Mn0 4 is unstable, but there is an indication of its stability in diethyl ether. The most important Mn(VII) compounds are MMP0 4 permanganates (where M is an alkali metal cation). KMp0 4 is obtained by electrolytic oxidation of K 2 Mn0 4 . In table. 8 shows the solubility of alkali metal permanganates in water.
Table 8
Solubility of alkali metal permanganates in water
Permanganate Ca (Mn0 4) 2 * 5H 2 0 is easily soluble in water and is used to sterilize drinking water.
Oxides. The following oxides of manganese are known: MnO - manganese monoxide or oxide; Mn 2 0 3 - manganese sesquioxide; Mn0 2 - manganese dioxide; Mn0 3 - manganese trioxide or manganese anhydride; Mn 2 0 7 - manganese heptoxide or manganese anhydride; Mn 3 0 4 is an intermediate manganese oxide, called red manganese oxide. All manganese oxides, with the exception of MnO, release chlorine under the action of HCl. Conc. H 2 S0 4 when heated, dissolves manganese oxides with the evolution of oxygen and the formation of MnS0 4 .
Mn(II) oxide is a green powder with shades from gray-green to dark green. MnO is obtained by calcining manganese carbonate or oxalate in an atmosphere of hydrogen or nitrogen, as well as by reducing higher oxides with hydrazine, hydrogen or carbon monoxide. Mn(II) hydroxide is separated from Mn(II) solutions in the form of a gelatinous white precipitate under the action of alkali metal hydroxides. Mn(OH) 2 is stable in air.
Black Mn 2 0 3 is formed by heating Mn0 2 in air to 550–900°C or by calcining Mn(II) salts in a stream of oxygen or air. When Mn 2 0 3 is heated in a stream of hydrogen at a temperature of about 230 ° C, a transition first to Mn 3 0 4 occurs, and at temperatures above 300 ° C, reduction to green monoxide occurs. When Mn 2 0 3 is dissolved in acids, either Mn(III) salts or Mn(II) and Mn0 2 salts are formed (depending on the nature of the acid and temperature).
Hydroxide of Mn (III)-Mn 2 0 3* H 2 0 oxide or manganese metahydroxide MnO (OH) occurs in nature in the form of manganite. Mn0 2 - a dark gray or almost black solid - is obtained by careful calcination of Mn (N0 3) 2 in air or by reduction of potassium permanganate in an alkaline medium. Mn0 2 is insoluble in water. When calcined above 530 ° C, it passes into Mn 3 0 4; Mn0 2 readily reacts with sulfurous acid to form manganese dithionate.
MnO 2 + 2H 2 S0 3 \u003d MnS 2 O 6 + 2H 2 0.
Cold conc. H 2 S0 4 does not act on Mn0 2 ; when heated to 110 ° C, Mn 2 (S0 4) 3 is formed, and at a higher temperature, Mn 2 (S0 4) 3 passes into MnS0 4. Manganese dioxide hydrate is obtained by oxidation of Mn(II) salts or by reduction in alkaline solutions of manganates or permanganates. MnO (OH) 2 or H 2 Mn0 3 - black or black-brown powder, practically insoluble in water. MnO from a mixture of MnO, Mn 2 O 3 and Mn O 2 can be separated by selective dissolution with a 6N solution of (NH 4) 2 S0 4 . MnO also dissolves well in NH 4 C1 solution. Mn 2 0 3 can be separated from Mn0 2 using a solution of metaphosphoric acid in conc. H 2 S0 4 . Mn0 2 does not dissolve in this solution even with prolonged heating. When Mn0 2 is fused with alkalis in the presence of oxidizing agents, salts of manganese acid H 2 Mn0 4 -manganates are formed. The free H 2 Mn0 4 released during acidification of manganate solutions is extremely unstable and decomposes according to the scheme
ZN 2 Mn0 4 = 2NMn0 4 + Mn0 2 + 2N 2 0.
Mp 2 0 7 is obtained by the action of conc. H 2 S0 4 on KMp0 4 . It is a heavy, shiny, greenish-brown oily substance, stable at ordinary temperatures, but decomposing with an explosion when heated. In a large amount of cold water, Mn 2 0 7 dissolves with the formation of NMn 0 4 (up to 20% of its concentration). Dark violet hygroscopic crystals HMn0 4 and HMn0 4* 2H 2 0 are obtained by adding 0.3 M H 2 S0 4 to 0.3 M solution of Ba(Mn0 4) 2 at a temperature<1° С с последующим удалением избытка воды и охлаждением смеси до - 75° С . При этой температуре НМп0 4 устойчива, выше +3° С она быстро разлагается. Кристаллическая НМп0 4 *2Н 2 0 устойчива при комнатной температуре в течение 10-30 мин.
Fluorides. MnF 2 is obtained by the interaction of MnCO 3 with hydrofluoric acid, the fluoride is soluble in dilute HF, conc. HCl and HNO 3 . Its solubility in water at 20 ° C is 1.06 g / 100 G. MnF 2 forms an unstable tetrahydrate MnF 2 * 4H 2 0, easily decomposing ammonia 3MnF 2 * 2NH 3, and with alkali metal fluorides - double salts MF * MnF 2 (where M is an alkali metal cation).
MnJ 3 - the only known halide Mn(III) - a wine-red solid, is formed by the action of fluorine on MnJ 2 at 250 ° C, by dissolving Mn 2 0 3 in HF, or by reacting KMn0 4 with a salt of Mn (P) in presence of HF. Crystallizes in the form of MnF 3 * 2H 2 0. MnF 3 decomposes with water according to the reaction
2MnF 3 + 2Н 2 0 = Mn0 2 + MnF 2 + 4HF.
With alkali metal fluorides, MnF 3 forms double salts MF*MnF 3 and 2MF*MnF 3 (where M is an alkali metal cation). Of the Mn(IV) fluoride compounds, only double salts 2MF*MnF 4 and MF*MnF 4 are known, which are golden-yellow transparent tabular crystals. Water decomposes 2KF*MnF 4 releasing Mn0 2* aq.
Chlorides. Anhydrous MnCl 2 is obtained by the action of dry HCl on oxide, carbonate or metallic manganese, as well as by burning metallic manganese in a stream of chlorine. Mn(II) chloride crystallizes as MnCl 2* 4H 2 0, which exists in two modifications. Crystal hydrates MnC1 2* 2H 2 0, MnC1 2* 5H 2 0, ZMpC1 2 *5H 2 O, MnC1 2* 6H 2 0 are also known. MpC1 2 is highly soluble in water (72.3 g/100 g at 25°C) and in absolute alcohol. In a flow of oxygen, MnCl 2 transforms into Mn 2 0 3 , and in a flow of HC1 at 1190°C it volatilizes. With alkali metal chlorides MnC1 2
forms double salts МCl*МпС1 2 . The following basic salts were obtained: MnOHCl, Mn 2 (OH) 3 Cl, Mn 3 (OH) 6 Cl. The existence of chloride complexes [Mn(H 2 0) 5 Cl] + , [Mn(H 2 0) 2 C1 4 ] 2- and others has been established. The composition of the complexes depends on the concentration of Cl - in solution, so when [Cl - ]>0.3 M a complex [Mn (H 2 0) 9 C1] + is formed, with [Cl - ]\u003e 5 M ─ [Mn (H 2 0) 2 C1 4] 2-. The stability constants [MpC1] + , [MpC1 2 ] and [MpC1 3 ] - respectively equal 3.85 0.15; 1.80 0.1 and 0.44 0.08. MnC1 3 is unknown, but double salts M 2 MnC1 6 have been obtained.
K 2 MPC1 5 is obtained by the reaction:
KMp0 4 + 8HC1 + KS1 \u003d K 2 MpCl 5 + 2C1 2 + 4H 2 0.
MnCl 4 appears to be formed first upon dissolution of pyrolusite in conc. HCl, however, it immediately decomposes with the elimination of chlorine. M 2 MnC1 6 compounds are more stable.
To 2 MPC1 6 is obtained by adding solutions of calcium permanganate and potassium chloride to strongly chilled 40% HCl.
Ca (Mn0 4) 2 + 16HC1 + 4KS1 \u003d 2K 2 MpC1 5 + CaC1 2 + 8H 2 0 + ZCl 2.
The same compound is obtained by reduction of KMn0 4 with diethyl ether in conc. HC1. Known chloroxides MnOS1 3, Mn0 2 C1 2,
Bromides. MnBr 2 is very similar in appearance and properties to MnC1 2 . However, the ability to form double salts in bromides is much lower than that of chlorides. MpBr 2 forms crystalline hydrates with one, two, four or six water molecules. The solubility of MnBr 2 * 4H 2 0 in water at 0 ° C is 127 g / 100 G. MpBr 3 and its double salts are unknown.
Iodides. MnJ 2 is also similar to MnC1 2, only it does not have the ability to form double salts at all, MnJ 2 forms a crystalline hydrate with one, two, four, six, eight or nine water molecules. When MnJ 2 interacts with alkali metal cyanides, double salts MnJ 2 *3MCN are formed. MnJ 3 and its double salts have not been obtained.
Nitrates. Mn(N0 3) 2 is obtained by the action of HN0 3 on MnC0 3 . Mn(N0 3) 2 crystallizes with one, three or six water molecules. Mn (N0 3) 2 * 6H 2 0 - slightly pink needle-shaped prisms, easily soluble in water and alcohol. At 160-200°C, it decomposes with the formation of Mn0 2 . The solubility of Mn (N0 3) 2 in water at 18 ° C is 134 g / 100 g. Anhydrous salt can attach up to 9 ammonia molecules. Mn(N0 3) 2 easily forms double salts with REE nitrates by fractional crystallization.
sulfates. MnSO 4 , one of the most stable Mn(II) compounds, is formed upon evaporation of almost all Mn(II) compounds with sulfuric acid. MnS0 4 crystallizes, depending on the conditions, with one, four, five, or seven water molecules. MnS0 4 * 5H 2 0 - reddish crystals, quite easily soluble in water and insoluble in alcohol. Anhydrous MnS0 4 is a white friable brittle crystalline mass. With sulfates of monovalent metals and ammonium MnS0 4 easily forms double salts M 2 S0 4 *MnSO 4 . The formation of Mn(II) complexes with S0 4 2 - composition , 2 - and 4 - was established, the stability constants of which are respectively equal to 8.5; 9; 9.3. Mn 2 (S0 4) 3 is obtained by reacting Mn(III) oxide or hydroxide with dilute H 2 S0 4 . It crystallizes as Mn 2 (S0 4) 3 H 2 S0 4 4H 2 0. When heated strongly, it turns into Mn 2 (S0 4) 3, which is highly hygroscopic and dissolves in H 2 S0 4 . With alkali metal sulfates, Mn 2 (S0 4) 3 forms two series of double salts: M 2 S0 4 * Mn 2 (S0 4) 3 and M, as well as alum-type salts. Cesium alum CsMn (S0 4) 2 * 12H 2 0 are the most stable. There are also double salts of Mn 2 (S0 4) 3 with sulfates. Fe (III), Cr (III), Al (III).
Mn (S0 4) 2 is obtained by oxidation of MnS0 4 with potassium permanganate at 50-60 ° C. Mn (S0 4) 2 dissolves in H 2 S0 4 (50-80%), forming a dark brown solution. In dilute sulfuric acid and water, it hydrolyzes with the release of MnO (OH) 2.
Sulfites. MnSO 3 is produced by the interaction of MnSO 3 with water containing S0 2 . Slightly soluble in water. Below 70° C, MnSO 3 crystallizes as a trihydrate, and at higher temperatures, as a monohydrate. With alkali metal sulfites MnS0 3 forms double salts M 2 S0 3 MnS0 3 .
Sulfides. MnS is obtained by the action of ammonium sulfide or alkali metal sulfide solutions on Mn(II) salts. With prolonged standing or heating, the dark-colored precipitate turns into a more stable green modification. Three modifications of MnS are known. -MnS - green crystals of the cubic system (alabandin), -MnS - red crystals of the cubic system, -MnS - red crystals of the hexagonal system. MnS is one of the most soluble sulfides, because with a change in the electronic structure of cations, the solubility of their sulfides in water changes:
Phosphates. From neutral solutions of Mn(II) salts with an excess of sodium phosphate, a crystalline hydrate of manganese orthophosphate Mn 3 (P0 4) 2 * 7H 2 0 precipitates in the form of a loose white precipitate. Under other conditions, other phosphates can be obtained: di- and metaphosphates, as well as acid phosphates. When chloride and ammonium phosphate and a small amount of ammonia are added to a solution of Mn (P) salts, a perfectly crystallizing double salt is formed - manganese - ammonium phosphate NH 4 MnP0 4 * H 2 0. This reaction is used in gravimetric analysis to determine manganese. Several Mn(III) phosphates are known, among them orthophosphate MnP0 4 * H 2 0 is gray-green in color, metaphosphate Mn(P0 3) 8 is red. The preparation of a manganese violet powder pigment with the empirical formula NH 4 MnP 2 0 7 is described. This substance decomposes at 120-340 ° C with the formation of a blue unstable product, which in turn decomposes at 340-460 ° C into [Mn 2 (P 4 0 12)] and [Mn 3 (P 3 0 9) 2]. When freshly precipitated Mn(OH) 3 reacts with a solution of H 3 P0 3 , a red-violet precipitate H[Mn(HP0 3) 2 ]*3H 2 0 is formed. Manganese phosphates are insoluble in water.
Phosphides. Properties of manganese phosphides are given in table. 9. Manganese monophosphide is obtained by heating a mixture of red phosphorus and electrolytic manganese sublimed in a vacuum, and Mn 2 R and MnR - by electrolysis of melts containing Mn 2 0 3 and sodium phosphate. Manganese phosphides dissolve in nitric acid and aqua regia, and the solubility increases with decreasing phosphorus content.
Table 9
Properties of manganese phosphides
|
Crystal structure |
T. pl., °С |
||
|
tetragonal | |||
|
Rhombic | |||
|
cubic | |||
|
Rhombic |
Silicides. Recently, the composition of manganese silicide MnSi 1.72 has been refined, which has semiconductor properties.
Arsenates. Simple manganese arsenates Mn 3 (As0 4) 2 H 2 0, MnHAs0 4 * H 2 0 and Mn(H 2 As0 4) 2, as well as double salts
NH 4 MnAs0 4 *6H 2 0.
hydrides. There is an indication of the formation of an unstable MnH hydride under the conditions of an electric discharge in hydrogen between manganese electrodes. Highly volatile manganese pentacarbonyl hydride MnH(CO) 5 was obtained, in which hydrogen, according to the study of infrared spectra, is directly bonded to manganese. The compound is colorless, so pl. -24.6°C.
Nitride. The physical and chemical properties of manganese nitrides have been little studied. These are unstable compounds (see Table 7); when heated, nitrogen is easily released. When Mn 2 N and Mn 3 N 2 are heated with hydrogen, ammonia is formed. Mn 4 N has strongly pronounced ferromagnetic properties. Mn 3 N 2 is obtained by heating manganese amalgam in dry nitrogen.
Borides. The existence of manganese borides MpV, MpV 2 , MpV 4 , Mn 2 V, Mn 3 V 4 and Mn 4 V has been established. Chemical resistance and melting point increase with increasing boron content. Manganese borides are obtained by sintering briquetted mixtures of electrolytic manganese powders with refined boron in purified argon at a temperature of 900-1350 ° C. All manganese borides dissolve easily in hydrochloric acid, the dissolution rate decreases as the boron content in them increases.
Carbonates. MnC0 3 *H 2 0 monohydrate is obtained by precipitation from a solution of Mn(P) salt saturated with C0 2 with acid sodium carbonate; dehydrated by heating under pressure in the absence of atmospheric oxygen. The solubility of MnC0 3 in water is low (PR = 9 * 10-11). In the dry state, it is stable in air; when wet, it easily oxidizes and darkens due to the formation of Mn 2 0 3 . The interaction of Mn(II) salts and soluble carbonates of other metals usually produces basic manganese carbonates.
peroxide derivatives. Mn(IV) are known as brown-black peracid salts H 4 Mn0 7 [HOMP(OOH) 3]. They can be obtained by the action of H 2 0 2 on a strongly cooled alkaline solution of KMn0 4 . At low concentrations of KOH, K 2 H 2 Mn0 7 is formed, in its more concentrated solutions, K 3 NMn0 7. Both connections are unstable.
Heteropoly compounds. Mn(P) with Mo0 3 forms a heteropolycompound (NH 4) 3 H 7 *3H 2 0, Mn(IV) with W0 3 forms a Na 2 H 6 compound.
Acetates. From a solution of MnCO 3 in acetic acid, Mn (C 2 H 3 O 2) 2 * 4H 2 0 crystallizes in the form of pale red needles that are stable in air. From an aqueous solution, Mn(C 2 H 3 0 2) 2 crystallizes with two water molecules. In dry air, the latter compound is stable; under the action of water, it undergoes hydrolysis. Mn (C 2 H 3 0 2) 3 is obtained by oxidation of Mn (C 2 H 3 0 2) 2 with potassium permanganate or chlorine. Only anhydrous acetate Mn (C 2 H 3 0 2) 3 is known, which is easily hydrolyzed.
Oxalates. MnS 2 0 4 is obtained by reacting hot solutions of oxalic acid and Mn(P) salts. In the cold, it crystallizes with three water molecules. In air, MPS 2 0 4 ZN 2 0 is unstable and transforms into MPS 2 0 4 -2H 2 0. Manganese oxalate is slightly soluble in water, with alkali metal oxalates it forms double salts M 2 C 2 0 4 -MpS 2 0 4. A stepwise formation of complexes MnS 2 0 4 , [Mn (C 2 0 4) 2 ] 2- and [Mn (C 2 0 4) 3 ] 4 - with instability constants, respectively, 7 * 10- 3, 1.26 * 10 - 2 and 1.77*10-2 Oxalates of manganese (III) are known only in the form of complex compounds with alkali metals. Potassium trioxalatomanganate K 3 [Mn (C 2 0 4) 3] * 3H 2 0 crystallizes in the form of dark red prisms. This compound decomposes in the light or on heating. The instability constants of the [Mn(C 2 0 4)] + , [Mn(C 2 0 4) 2 ]- and [Mn(C 2 0 4) 3] 3- complexes, respectively, are equal to 1.05*10-10; 2.72*10-17; 3.82*10-20.
Formates. The formation of Mn(P) complexes with HCOO- [Mn(HCOO)] + and [Mn(HCOO) 2 ] complexes with stability constants of 3 and 15, respectively, was established.
Mn(P) s wine, lemon, salicylic, apple and other acids forms complexes in an aqueous solution with a ratio of Mn to anion 1: 1, in ethyl alcohol, acetone and dioxane - with a ratio of 1: 2. The complex formation of Mn(P) with ascorbic acid. The complexes formed in an alkaline medium have the general formula n - , where A is the anion of ascorbic acid. FROM kojeva Mn(P) acid forms complex compounds [MnA(H 2 0) 2 ] + and MnA 2 (where A is the anion of kojic acid), the stability of which is characterized by the values lg K l = 3.95 and lg K 2 = 2.83 respectively.
Kupferon with manganese forms a poorly soluble compound Mn(C 6 H 5 0 2 N 2) 2 . The solubility of the precipitate increases with an excess of manganese salt and cupferon.
formaldoxime when interacting with Mn(P) in an alkaline medium, it gives a colorless complex compound, which quickly oxidizes in air to a red-brown, very stable complex 2 -.
Sodium diethyldithiocarbamate(DDTCNa) with Mn(II) forms a light yellow precipitate, in air with an excess of the reagent it transforms into a brown-violet complex Mn(DDTC) 3 . Complex instability constant
2.8*10-5. The solubility of manganese diethyldithiocarbamate in various solvents is given in Table. ten.
Table 10
Solubility of manganese diethyldithiocarbamate in various solvents
|
Dissolve |
Solubility |
Solvent |
Solubility |
||
|
g/100 ml solvent |
g*mol/1000 ml solvent |
g/100 ml solvent |
g*mol/1000 ml solvent |
||
|
Water Chloroform Carbon tetrachloride |
3,3*10- 4 0,364 0,202 |
Benzene Butyl Acetate | |||
ComplexonIII forms with manganese (II) complex Na 2 * 6H 2 0 - a white crystalline substance with a pinkish tinge, highly soluble in water.
Manganese complexonates have also been isolated - H 2 MnY * 4H 2 0; (NH 4) 2 MnY*4H 2 O; Mn 2 Y*9H 2 0, where Y 4- is the anion of ethylenediaminetetraacetic acid.
Other organic compounds of manganese. The instability constants of manganese complexes with methylthymol blue and xylenol orange are 0.089*10-6 and 1.29*10-6, respectively. Manganese reacts with dithizone only at pH > 7. The composition of manganese dithizonate corresponds to the ratio of metal to dithizone equal to 1:2. Manganese forms colored complex compounds with 1-(2-pyridylazo)-naphthol-2 (PAN), 4-(2- pyridylazo)-resolving (PAR), 8-hydroxyquinoline, which are poorly soluble in water (with the exception of the complex with PAR), are highly soluble in organic solvents and are used for the photometric determination of manganese. For the photometric determination of manganese, its complexes with benzenehydroxamic acid, anthranylhydroxamic acid, thenoyltrifluoroacetone, thioxin, and other organic reagents are also used. With PAR and 9-salicylfluorone, manganese forms complexes with a Mn to anion ratio of 1:2, with instability constants of 3.9*10-12 and 5.5*10-14, respectively.
