Salt formula. Chemical formula: table salt
| Cations | Anions | |||||||||
| F- | Cl- | br- | I- | S2- | NO 3 - | CO 3 2- | SiO 3 2- | SO 4 2- | PO 4 3- | |
| Na+ | R | R | R | R | R | R | R | R | R | R |
| K+ | R | R | R | R | R | R | R | R | R | R |
| NH4+ | R | R | R | R | R | R | R | R | R | R |
| Mg2+ | RK | R | R | R | M | R | H | RK | R | RK |
| Ca2+ | NK | R | R | R | M | R | H | RK | M | RK |
| Sr2+ | NK | R | R | R | R | R | H | RK | RK | RK |
| Ba 2+ | RK | R | R | R | R | R | H | RK | NK | RK |
| sn 2+ | R | R | R | M | RK | R | H | H | R | H |
| Pb 2+ | H | M | M | M | RK | R | H | H | H | H |
| Al 3+ | M | R | R | R | G | R | G | NK | R | RK |
| Cr3+ | R | R | R | R | G | R | G | H | R | RK |
| Mn2+ | R | R | R | R | H | R | H | H | R | H |
| Fe2+ | M | R | R | R | H | R | H | H | R | H |
| Fe3+ | R | R | R | - | - | R | G | H | R | RK |
| Co2+ | M | R | R | R | H | R | H | H | R | H |
| Ni2+ | M | R | R | R | RK | R | H | H | R | H |
| Cu2+ | M | R | R | - | H | R | G | H | R | H |
| Zn2+ | M | R | R | R | RK | R | H | H | R | H |
| CD 2+ | R | R | R | R | RK | R | H | H | R | H |
| Hg2+ | R | R | M | NK | NK | R | H | H | R | H |
| Hg 2 2+ | R | NK | NK | NK | RK | R | H | H | M | H |
| Ag+ | R | NK | NK | NK | NK | R | H | H | M | H |
Legend:
P - the substance is highly soluble in water; M - slightly soluble; H - practically insoluble in water, but easily soluble in weak or dilute acids; RK - insoluble in water and soluble only in strong inorganic acids; NK - insoluble neither in water nor in acids; G - completely hydrolyzes upon dissolution and does not exist in contact with water. A dash means that such a substance does not exist at all.
In aqueous solutions, salts completely or partially dissociate into ions. Salts of weak acids and/or weak bases undergo hydrolysis. Aqueous salt solutions contain hydrated ions, ion pairs, and more complex chemical forms, including hydrolysis products, etc. A number of salts are also soluble in alcohols, acetone, acid amides, and other organic solvents.
From aqueous solutions, salts can crystallize in the form of crystalline hydrates, from non-aqueous solutions - in the form of crystalline solvates, for example CaBr 2 3C 2 H 5 OH.
Data on various processes occurring in water-salt systems, on the solubility of salts in their joint presence depending on temperature, pressure and concentration, on the composition of solid and liquid phases can be obtained by studying the solubility diagrams of water-salt systems.
General methods for the synthesis of salts.
1. Obtaining medium salts:
1) metal with non-metal: 2Na + Cl 2 = 2NaCl
2) metal with acid: Zn + 2HCl = ZnCl 2 + H 2
3) metal with a salt solution of a less active metal Fe + CuSO 4 = FeSO 4 + Cu
4) basic oxide with acid oxide: MgO + CO 2 = MgCO 3
5) basic oxide with acid CuO + H 2 SO 4 \u003d CuSO 4 + H 2 O
6) bases with acidic oxide Ba (OH) 2 + CO 2 = BaCO 3 + H 2 O
7) bases with acid: Ca (OH) 2 + 2HCl \u003d CaCl 2 + 2H 2 O
8) acid salts: MgCO 3 + 2HCl = MgCl 2 + H 2 O + CO 2
BaCl 2 + H 2 SO 4 \u003d BaSO 4 + 2HCl
9) a base solution with a salt solution: Ba (OH) 2 + Na 2 SO 4 \u003d 2NaOH + BaSO 4
10) solutions of two salts 3CaCl 2 + 2Na 3 PO 4 = Ca 3 (PO 4) 2 + 6NaCl
2. Obtaining acid salts:
1. Interaction of an acid with a lack of a base. KOH + H 2 SO 4 \u003d KHSO 4 + H 2 O
2. Interaction of a base with an excess of acid oxide
Ca(OH) 2 + 2CO 2 = Ca(HCO 3) 2
3. Interaction of an average salt with acid Ca 3 (PO 4) 2 + 4H 3 PO 4 \u003d 3Ca (H 2 PO 4) 2
3. Obtaining basic salts:
1. Hydrolysis of salts formed by a weak base and a strong acid
ZnCl 2 + H 2 O \u003d Cl + HCl
2. Addition (drop by drop) of small amounts of alkalis to solutions of medium metal salts AlCl 3 + 2NaOH = Cl + 2NaCl
3. Interaction of salts of weak acids with medium salts
2MgCl 2 + 2Na 2 CO 3 + H 2 O \u003d 2 CO 3 + CO 2 + 4NaCl
4. Obtaining complex salts:
1. Reactions of salts with ligands: AgCl + 2NH 3 = Cl
FeCl 3 + 6KCN] = K 3 + 3KCl
5. Obtaining double salts:
1. Joint crystallization of two salts:
Cr 2 (SO 4) 3 + K 2 SO 4 + 24H 2 O \u003d 2 + NaCl
4. Redox reactions due to the properties of the cation or anion. 2KMnO 4 + 16HCl = 2MnCl 2 + 2KCl + 5Cl 2 + 8H 2 O
2. Chemical properties of acid salts:
1. Thermal decomposition with the formation of medium salt
Ca (HCO 3) 2 \u003d CaCO 3 + CO 2 + H 2 O
2. Interaction with alkali. Obtaining medium salt.
Ba(HCO 3) 2 + Ba(OH) 2 = 2BaCO 3 + 2H 2 O
3. Chemical properties of basic salts:
1. Thermal decomposition. 2 CO 3 \u003d 2CuO + CO 2 + H 2 O
2. Interaction with acid: the formation of an average salt.
Sn(OH)Cl + HCl = SnCl 2 + H 2 O
4. Chemical properties of complex salts:
1. Destruction of complexes due to the formation of poorly soluble compounds:
2Cl + K 2 S \u003d CuS + 2KCl + 4NH 3
2. Exchange of ligands between the outer and inner spheres.
K 2 + 6H 2 O \u003d Cl 2 + 2KCl
5. Chemical properties of double salts:
1. Interaction with alkali solutions: KCr(SO 4) 2 + 3KOH = Cr(OH) 3 + 2K 2 SO 4
2. Recovery: KCr (SO 4) 2 + 2H ° (Zn, diluted H 2 SO 4) \u003d 2CrSO 4 + H 2 SO 4 + K 2 SO 4
The raw materials for the industrial production of a number of chloride salts, sulfates, carbonates, Na, K, Ca, Mg borates are sea and ocean water, natural brines formed during its evaporation, and solid deposits of salts. For a group of minerals that form sedimentary salt deposits (sulfates and chlorides of Na, K and Mg), the code name “natural salts” is used. The largest deposits of potassium salts are located in Russia (Solikamsk), Canada and Germany, powerful deposits of phosphate ores - in North Africa, Russia and Kazakhstan, NaNO3 - in Chile.
Salts are used in food, chemical, metallurgical, glass, leather, textile industries, agriculture, medicine, etc.
The main types of salts
1. Borates (oxoborates), salts of boric acids: metaboric HBO 2, orthoboric H 3 BO 3 and polyboric acids not isolated in the free state. According to the number of boron atoms in the molecule, they are divided into mono-, di, tetra-, hexaborates, etc. Borates are also called according to the acids that form them and according to the number of moles of B 2 O 3 per 1 mole of the basic oxide. So various metaborates can be called monoborates if they contain an anion B (OH) 4 or a chain anion (BO 2) n n - diborates - if they contain a chain double anion (B 2 O 3 (OH) 2) n 2n- triborates - if they contain a ring anion (B 3 O 6) 3-.
The structures of borates include boron-oxygen groups - “blocks” containing from 1 to 6, and sometimes 9 boron atoms, for example:
The coordination number of boron atoms is 3 (boron-oxygen triangular groups) or 4 (tetrahedral groups). Boron-oxygen groups are the basis of not only island, but also more complex structures - chain, layered and framework polymerized. The latter are formed as a result of the elimination of water in the molecules of hydrated borates and the appearance of bridging bonds through oxygen atoms; the process is sometimes accompanied by the breaking of the B-O bond within the polyanions. Polyanions can attach side groups - boron-oxygen tetrahedra or triangles, their dimers or extraneous anions.
Ammonium, alkali, as well as other metals in the +1 oxidation state most often form hydrated and anhydrous metaborates of the MBO 2 type, M 2 B 4 O 7 tetraborates, MB 5 O 8 pentaborates, and also M 4 B 10 O 17 decaborates n H 2 O. Alkaline earth and other metals in the + 2 oxidation state usually give hydrated metaborates, M 2 B 6 O 11 triborates and MB 6 O 10 hexaborates. as well as anhydrous meta-, ortho- and tetraborates. Metals in the + 3 oxidation state are characterized by hydrated and anhydrous MBO 3 orthoborates.
Borates are colorless amorphous substances or crystals (mainly with a low-symmetrical structure - monoclinic or rhombic). For anhydrous borates, the melting points are in the range from 500 to 2000 °C; the most high-melting metaborates are alkali and ortho- and metaborates of alkaline earth metals. Most borates easily form glasses when their melts are cooled. The hardness of hydrated borates on the Mohs scale is 2-5, anhydrous - up to 9.
Hydrated monoborates lose water of crystallization up to ~180°C, polyborates - at 300-500°C; elimination of water due to OH groups , coordinated around boron atoms occurs up to ~750°C. With complete dehydration, amorphous substances are formed, which at 500-800 ° C in most cases undergo “borate rearrangement” - crystallization, accompanied (for polyborates) by partial decomposition with the release of B 2 O 3.
Alkali metal, ammonium and T1(I) borates are soluble in water (especially meta- and pentaborates), hydrolyze in aqueous solutions (solutions have an alkaline reaction). Most borates are easily decomposed by acids, in some cases by the action of CO 2; and SO2;. Borates of alkaline earth and heavy metals interact with solutions of alkalis, carbonates and bicarbonates of alkali metals. Anhydrous borates are chemically more stable than hydrated ones. With some alcohols, in particular with glycerol, borates form water-soluble complexes. Under the action of strong oxidizing agents, in particular H 2 O 2, or during electrochemical oxidation, borates are converted into peroxoborates .
About 100 natural borates are known, which are mainly salts of Na, Mg, Ca, Fe.
Hydrated borates are obtained by: neutralization of H 3 BO 3 with metal oxides, hydroxides or carbonates; exchange reactions of alkali metal borates, most often Na, with salts of other metals; the reaction of mutual transformation of sparingly soluble borates with aqueous solutions of alkali metal borates; hydrothermal processes using alkali metal halides as mineralizing additives. Anhydrous borates are obtained by fusion or sintering of B 2 O 3 with metal oxides or carbonates or by dehydration of hydrates; single crystals are grown in solutions of borates in molten oxides, for example Bi 2 O 3 .
Borates are used: to obtain other boron compounds; as components of the charge in the production of glasses, glazes, enamels, ceramics; for fire-resistant coatings and impregnations; as components of fluxes for refining, welding and soldering of metal”; as pigments and fillers of paints and varnishes; as mordants in dyeing, corrosion inhibitors, components of electrolytes, phosphors, etc. Borax and calcium borates are most widely used.
2. Halides, chemical compounds of halogens with other elements. Halides usually include compounds in which the halogen atoms have a higher electronegativity than another element. Halides do not form He, Ne and Ar. To simple, or binary, halides EX n (n- most often an integer from 1 for monohalides to 7 for IF 7, and ReF 7, but can also be fractional, for example 7/6 for Bi 6 Cl 7) include, in particular, salts of hydrohalic acids and interhalogen compounds (for example, halofluorides). There are also mixed halides, polyhalides, hydrohalides, oxohalides, oxyhalides, hydroxohalides, thiohalides, and complex halides. The oxidation state of halogens in halides is usually -1.
According to the nature of the element-halogen bond, simple halides are divided into ionic and covalent. In reality, the relationships are of a mixed nature with the predominance of the contribution of one or another component. The halides of alkali and alkaline earth metals, as well as many mono- and dihalides of other metals, are typical salts in which the ionic nature of the bond prevails. Most of them are relatively refractory, low volatile, highly soluble in water; in aqueous solutions, they almost completely dissociate into ions. The properties of salts are also possessed by trihalides of rare earth elements. The water solubility of ionic halides generally decreases from iodides to fluorides. Chlorides, bromides and iodides Ag + , Сu + , Hg + and Pb 2+ are poorly soluble in water.
An increase in the number of halogen atoms in metal halides or the ratio of the metal charge to the radius of its ion leads to an increase in the covalent component of the bond, a decrease in solubility in water and thermal stability of halides, an increase in volatility, an increase in oxidization, ability and tendency to hydrolysis. These dependences are observed for metal halides of the same period and in the series of halides of the same metal. They are easy to trace on the example of thermal properties. For example, for metal halides of the 4th period, the melting and boiling points are respectively 771 and 1430°C for KC1, 772 and 1960°C for CaCl 2, 967 and 975°C for ScCl 3 , -24.1 and 136°C for TiCl 4 . For UF 3, the melting point is ~ 1500 ° C, UF 4 1036 ° C, UF 5 348 ° C, UF 6 64.0 ° C. In the series of EC compounds n with the same n the covalence of the bond usually increases on going from fluorides to chlorides and decreases on going from the latter to bromides and iodides. So, for AlF 3, the sublimation temperature is 1280 ° C, A1C1 3 180 ° C, the boiling point of A1Br 3 is 254.8 ° C, AlI 3 407 ° C. In the series ZrF 4 , ZrCl 4 ZrBr 4 , ZrI 4 the sublimation temperature is 906, 334, 355 and 418°C, respectively. In the MF ranks n and MS1 n where M is a metal of one subgroup, the covalence of the bond decreases with increasing atomic mass of the metal. There are few metal fluorides and chlorides with approximately the same contribution of the ionic and covalent bond components.
The average element-halogen bond energy decreases when moving from fluorides to iodides and with increasing n(see table).
Many metal halides containing isolated or bridging O atoms (respectively, oxo- and oxyhalides), for example, vanadium oxotrifluoride VOF 3, niobium dioxyfluoride NbO 2 F, tungsten dioxodiiodide WO 2 I 2.
Complex halides (halogenometallates) contain complex anions in which the halogen atoms are ligands, for example, potassium hexachloroplatinate (IV) K 2 , sodium heptafluorotantalate (V) Na, lithium hexafluoroarsenate (V) Li. Fluoro-, oxofluoro- and chlorometallates have the highest thermal stability. By the nature of the bonds, ionic compounds with cations NF 4 + , N 2 F 3 + , C1F 2 + , XeF + and others are close to complex halides.
Many halides are characterized by association and polymerization in the liquid and gas phases with the formation of bridge bonds. The most prone to this are the halides of metals of groups I and II, AlCl 3 , pentafluorides of Sb and transition metals, oxofluorides of the composition MOF 4 . Known halides with a metal-metal bond, for example. Cl-Hg-Hg-Cl.
Fluorides differ significantly in properties from other halides. However, in simple halides, these differences are less pronounced than in the halogens themselves, and in complex halides, they are less pronounced than in simple ones.
Many covalent halides (especially fluorides) are strong Lewis acids, e.g. AsF 5 , SbF 5 , BF 3 , A1C1 3 . Fluorides are part of superacids. Higher halides are reduced by metals and hydrogen, for example:
5WF 6 + W = 6WF 5
TiCl 4 + 2Mg \u003d Ti + 2MgCl 2
UF 6 + H 2 \u003d UF 4 + 2HF
Metal halides of groups V-VIII, except for Cr and Mn, are reduced by H 2 to metals, for example:
WF 6 + ZN 2 = W + 6HF
Many covalent and ionic metal halides interact with each other to form complex halides, for example:
KC1 + TaCl 5 = K
The lighter halogens can displace the heavier ones from the halides. Oxygen can oxidize halides with the release of C1 2 , Br 2 , and I 2 . One of the characteristic reactions of covalent halides is the interaction with water (hydrolysis) or its vapors when heated (pyrohydrolysis), leading to the formation of oxides, oxy- or oxo halides, hydroxides and hydrogen halides.
Halides are obtained directly from the elements, by the interaction of hydrogen halides or hydrohalic acids with elements, oxides, hydroxides or salts, as well as by exchange reactions.
Halides are widely used in engineering as starting materials for the production of halogens, alkali and alkaline earth metals, and as components of glasses and other inorganic materials; they are intermediate products in the production of rare and some non-ferrous metals, U, Si, Ge, etc.
In nature, halides form separate classes of minerals, which include fluorides (eg, the minerals fluorite, cryolite) and chlorides (sylvite, carnallite). Bromine and iodine are present in some minerals as isomorphic impurities. Significant amounts of halides are found in the water of the seas and oceans, in salt and underground brines. Some halides, such as NaCl, KC1, CaCl 2, are part of living organisms.
3. Carbonates (from lat. carbo, genus case carbonis coal), salts of carbonic acid. There are medium carbonates with the CO 3 2- anion and acidic, or bicarbonates (obsolete bicarbonates), with the HCO 3 - anion. Carbonates are crystalline substances. Most of the medium metal salts in the oxidation state + 2 crystallize into a hexagon. lattice type of calcite or rhombic type of aragonite.
Of the medium carbonates, only salts of alkali metals, ammonium and Tl (I) dissolve in water. As a result of significant hydrolysis, their solutions have an alkaline reaction. The most difficult soluble metal carbonates in the oxidation state + 2. On the contrary, all bicarbonates are highly soluble in water. During exchange reactions in aqueous solutions between metal salts and Na 2 CO 3, precipitates of medium carbonates are formed when their solubility is much lower than that of the corresponding hydroxides. This is the case for Ca, Sr and their analogues, lanthanides, Ag(I), Mn(II), Pb(II), and Cd(II). The remaining cations, when interacting with dissolved carbonates as a result of hydrolysis, can give not average, but basic carbonates or even hydroxides. Medium carbonates containing multiply charged cations can sometimes be precipitated from aqueous solutions in the presence of a large excess of CO 2 .
The chemical properties of carbonates are due to their belonging to the class of inorganic salts of weak acids. The characteristic features of carbonates are associated with their poor solubility, as well as the thermal instability of both the crabonates themselves and H 2 CO 3 . These properties are used in the analysis of crabonates, based either on their decomposition by strong acids and the quantitative absorption of the CO 2 released in this case by an alkali solution, or on the precipitation of the CO 3 2- ion from the solution in the form of ВаСО 3 . Under the action of an excess of CO 2 on a precipitate of an average carbonate in a solution, a bicarbonate is formed, for example: CaCO 3 + H 2 O + CO 2 \u003d Ca (HCO 3) 2. The presence of bicarbonates in natural water determines its temporary hardness. Hydrocarbonates upon slight heating already at low temperatures are again converted into medium carbonates, which, upon heating, decompose to oxide and CO 2. The more active the metal, the higher the decomposition temperature of its carbonate. So, Na 2 CO 3 melts without decomposition at 857 °C, and for Ca, Mg and Al carbonates, the equilibrium decomposition pressures reach 0.1 MPa at temperatures of 820, 350 and 100 °C, respectively.
Carbonates are very widespread in nature, which is due to the participation of CO 2 and H 2 O in the processes of mineral formation. carbonates play a large role in global equilibriums between gaseous CO 2 in the atmosphere and dissolved CO 2 ;
and HCO 3 - and CO 3 2- ions in the hydrosphere and solid salts in the lithosphere. The most important minerals are CaCO 3 calcite, MgCO 3 magnesite, FeCO 3 siderite, ZnCO 3 smithsonite and some others. Limestone consists mainly of calcite or calcite skeletal remains of organisms, rarely of aragonite. Natural hydrated carbonates of alkali metals and Mg are also known (for example, MgCO 3 ZH 2 O, Na 2 CO 3 10H 2 O), double carbonates [for example, dolomite CaMg (CO 3) 2, throne Na 2 CO 3 NaHCO 3 2H 2 O] and basic [malachite CuCO 3 Cu(OH) 2, hydrocerussite 2РbСО 3 Pb(OH) 2].
The most important are potassium carbonate, calcium carbonate and sodium carbonate. Many natural carbonates are very valuable metal ores (for example, carbonates of Zn, Fe, Mn, Pb, Cu). Bicarbonates play an important physiological role, being buffer substances that regulate the constancy of blood pH.
4. Nitrates, salts of nitric acid HNO 3. Known for almost all metals; exist both in the form of anhydrous salts M (NO 3) n (n- the degree of oxidation of the metal M), and in the form of crystalline hydrates M (NO 3) n x H 2 O ( X= 1-9). From aqueous solutions at a temperature close to room temperature, only alkali metal nitrates crystallize anhydrous, the rest - in the form of crystalline hydrates. The physicochemical properties of anhydrous and hydrated nitrate of the same metal can be very different.
Anhydrous crystalline compounds of d-element nitrates are colored. Conventionally, nitrates can be divided into compounds with a predominantly covalent type of bond (salts of Be, Cr, Zn, Fe, and other transition metals) and with a predominantly ionic type of bond (salts of alkali and alkaline earth metals). Ionic nitrates are characterized by higher thermal stability, the predominance of crystal structures of higher symmetry (cubic), and the absence of splitting of the nitrate ion bands in the IR spectra. Covalent nitrates have a higher solubility in organic solvents, lower thermal stability, their IR spectra are more complex; some covalent nitrates are volatile at room temperature, and when dissolved in water, they partially decompose with the release of nitrogen oxides.
All anhydrous nitrates show strong oxidizing properties due to the presence of the NO 3 - ion, while their oxidizing ability increases when moving from ionic to covalent nitrates. The latter decompose in the range of 100-300°C, ionic - at 400-600°C (NaNO 3 , KNO 3 and some others melt when heated). Decomposition products in solid and liquid phases. are sequentially nitrites, oxonitrates and oxides, sometimes - free metals (when the oxide is unstable, for example Ag 2 O), and in the gas phase - NO, NO 2, O 2 and N 2. The composition of the decomposition products depends on the nature of the metal and its degree of oxidation, heating rate, temperature, composition of the gaseous medium, and other conditions. NH 4 NO 3 detonates, and when heated rapidly it can decompose with an explosion, in this case N 2 , O 2 and H 2 O are formed; when heated slowly, it decomposes into N 2 O and H 2 O.
The free NO 3 - ion in the gas phase has the geometric structure of an equilateral triangle with an N atom in the center, ONO angles ~ 120°, and N-O bond lengths of 0.121 nm. In crystalline and gaseous nitrates, the NO 3 ion - basically retains its shape and size, which determines the space and structure of nitrates. Ion NO 3 - can act as a mono-, bi-, tridentate or bridging ligand, so nitrates are characterized by a wide variety of types of crystal structures.
Transition metals in high oxidation states due to steric. difficulties cannot form anhydrous nitrates, and they are characterized by oxonitrates, for example UO 2 (NO 3) 2, NbO (NO 3) 3. Nitrates form a large number of double and complex salts with the NO 3 ion - in the inner sphere. In aqueous media, as a result of hydrolysis, transition metal cations form hydroxonitrates (basic nitrates) of variable composition, which can also be isolated in the solid state.
Hydrated nitrates differ from anhydrous ones in that in their crystal structures, the metal ion is in most cases associated with water molecules, and not with the NO 3 ion. Therefore, they dissolve better than anhydrous nitrates in water, but worse - in organic solvents, weaker oxidizing agents melt incongruently in crystallization water in the range of 25-100°C. When hydrated nitrates are heated, as a rule, anhydrous nitrates are not formed, but thermolysis occurs with the formation of hydroxonitrates and then oxonitrates and metal oxides.
In many of their chemical properties, nitrates are similar to other inorganic salts. The characteristic features of nitrates are due to their very high solubility in water, low thermal stability and the ability to oxidize organic and inorganic compounds. During the reduction of nitrates, a mixture of nitrogen-containing products NO 2 , NO, N 2 O, N 2 or NH 3 is formed with the predominance of one of them depending on the type of reducing agent, temperature, reaction of the medium, and other factors.
Industrial methods for obtaining nitrates are based on the absorption of NH 3 by HNO 3 solutions (for NH 4 NO 3) or on the absorption of nitrous gases (NO + NO 2) by alkali or carbonate solutions (for alkali metal nitrates, Ca, Mg, Ba), as well as on various exchange reactions of metal salts with HNO 3 or alkali metal nitrates. In the laboratory, to obtain anhydrous nitrates, reactions of transition metals or their compounds with liquid N 2 O 4 and its mixtures with organic solvents or reactions with N 2 O 5 are used.
Nitrates Na, K (sodium and potassium nitrate) are found in the form of natural deposits.
Nitrates are used in many industries. Ammonium nitrite (ammonium nitrate) - the main nitrogen-containing fertilizer; nitrates of alkali metals and Ca are also used as fertilizers. Nitrates - components of rocket fuels, pyrotechnic compositions, pickling solutions for dyeing fabrics; they are used for hardening metals, food preservation, as medicines, and for the production of metal oxides.
Nitrates are toxic. They cause pulmonary edema, cough, vomiting, acute cardiovascular insufficiency, etc. The lethal dose of nitrates for humans is 8-15 g, the allowable daily intake is 5 mg / kg. For the sum of Na, K, Ca, NH3 nitrates MPC: in water 45 mg/l", in soil 130 mg/kg (hazard class 3); in vegetables and fruits (mg/kg) - potatoes 250, late white cabbage 500, late carrots 250, beets 1400, onions 80, zucchini 400, melons 90, watermelons, grapes, apples, pears 60. Non-compliance with agrotechnical recommendations, excessive fertilization dramatically increases the content of nitrates in agricultural products, surface runoff from fields ( 40-5500 mg/l), ground water.
5. Nitrites, salts of nitrous acid HNO 2. First of all, nitrites of alkali metals and ammonium are used, less - alkaline earth and Z d-metals, Pb and Ag. There is only fragmentary information about the nitrites of other metals.
Metal nitrites in the +2 oxidation state form crystal hydrates with one, two or four water molecules. Nitrites form double and triple salts, for example. CsNO 2 AgNO 2 or Ba (NO 2) 2 Ni (NO 2) 2 2KNO 2, as well as complex compounds, such as Na 3.
Crystal structures are known only for a few anhydrous nitrites. The NO 2 anion has a non-linear configuration; ONO angle 115°, H-O bond length 0.115 nm; the type of connection M-NO 2 is ionic-covalent.
K, Na, Ba nitrites are well soluble in water, Ag, Hg, Cu nitrites are poorly soluble. With increasing temperature, the solubility of nitrites increases. Almost all nitrites are poorly soluble in alcohols, ethers, and low-polarity solvents.
Nitrites are thermally unstable; melt without decomposition only nitrites of alkali metals, nitrites of other metals decompose at 25-300 °C. The mechanism of nitrite decomposition is complex and includes a number of parallel-sequential reactions. The main gaseous decomposition products are NO, NO 2, N 2 and O 2, solid ones are metal oxide or elemental metal. The release of a large amount of gases causes the explosive decomposition of some nitrites, for example NH 4 NO 2, which decomposes into N 2 and H 2 O.
The characteristic features of nitrites are associated with their thermal instability and the ability of the nitrite ion to be both an oxidizing agent and a reducing agent, depending on the medium and the nature of the reagents. In a neutral environment, nitrites are usually reduced to NO, in an acidic environment they are oxidized to nitrates. Oxygen and CO 2 do not interact with solid nitrites and their aqueous solutions. Nitrites contribute to the decomposition of nitrogen-containing organic substances, in particular amines, amides, etc. With organic halides RXH. react to form both RONO nitrites and RNO 2 nitro compounds.
The industrial production of nitrites is based on the absorption of nitrous gas (a mixture of NO + NO 2) with solutions of Na 2 CO 3 or NaOH with successive crystallization of NaNO 2; nitrites of other metals in industry and laboratories are obtained by the exchange reaction of metal salts with NaNO 2 or by the reduction of nitrates of these metals.
Nitrites are used for the synthesis of azo dyes, in the production of caprolactam, as oxidizing and reducing agents in the rubber, textile and metalworking industries, as food preservatives. Nitrites such as NaNO 2 and KNO 2 are toxic, causing headache, vomiting, respiratory depression, etc. When NaNO 2 is poisoned, methemoglobin is formed in the blood, erythrocyte membranes are damaged. Perhaps the formation of nitrosamines from NaNO 2 and amines directly in the gastrointestinal tract.
6. Sulfates, salts of sulfuric acid. Medium sulfates with the anion SO 4 2- are known, acidic, or hydrosulfates, with the anion HSO 4 - , basic, containing along with the anion SO 4 2- - OH groups, for example Zn 2 (OH) 2 SO 4 . There are also double sulfates, which include two different cations. These include two large groups of sulfates - alum , as well as chenites M 2 E (SO 4) 2 6H 2 O , where M is a singly charged cation, E is Mg, Zn and other doubly charged cations. Known triple sulfate K 2 SO 4 MgSO 4 2CaSO 4 2H 2 O (mineral polygalite), double basic sulfates, for example, minerals of the alunite and jarosite groups M 2 SO 4 Al 2 (SO 4) 3 4Al (OH 3 and M 2 SO 4 Fe 2 (SO 4) 3 4Fe (OH) 3, where M is a singly charged cation.Sulfates can be part of mixed salts, for example 2Na 2 SO 4 Na 2 CO 3 (mineral berkite), MgSO 4 KCl 3H 2 O (kainite) .
Sulfates are crystalline substances, medium and acidic, in most cases they are highly soluble in water. Slightly soluble sulfates of calcium, strontium, lead and some others, practically insoluble BaSO 4 , RaSO 4 . Basic sulfates are usually sparingly soluble or practically insoluble, or hydrolyzed by water. Sulfates can crystallize from aqueous solutions in the form of crystalline hydrates. The crystalline hydrates of some heavy metals are called vitriol; copper sulfate СuSO 4 5H 2 O, ferrous sulfate FeSO 4 7H 2 O.
Medium alkali metal sulfates are thermally stable, while acid sulfates decompose when heated, turning into pyrosulfates: 2KHSO 4 \u003d H 2 O + K 2 S 2 O 7. Average sulfates of other metals, as well as basic sulfates, when heated to sufficiently high temperatures, as a rule, decompose with the formation of metal oxides and the release of SO 3 .
Sulfates are widely distributed in nature. They are found in the form of minerals, such as gypsum CaSO 4 H 2 O, mirabilite Na 2 SO 4 10H 2 O, and are also part of sea and river water.
Many sulfates can be obtained by the interaction of H 2 SO 4 with metals, their oxides and hydroxides, as well as the decomposition of salts of volatile acids with sulfuric acid.
Inorganic sulfates are widely used. For example, ammonium sulfate is a nitrogen fertilizer, sodium sulfate is used in the glass, paper industry, viscose production, etc. Natural sulfate minerals are raw materials for the industrial production of compounds of various metals, building materials, etc.
7.sulfites, salts of sulfurous acid H 2 SO 3 . There are medium sulfites with the anion SO 3 2- and acidic (hydrosulfites) with the anion HSO 3 - . Medium sulfites are crystalline substances. Ammonium and alkali metal sulfites are highly soluble in water; solubility (g in 100 g): (NH 4) 2 SO 3 40.0 (13 ° C), K 2 SO 3 106.7 (20 ° C). In aqueous solutions they form hydrosulfites. Sulfites of alkaline earth and some other metals are practically insoluble in water; solubility of MgSO 3 1 g in 100 g (40°C). Known crystalline hydrates (NH 4) 2 SO 3 H 2 O, Na 2 SO 3 7H 2 O, K 2 SO 3 2H 2 O, MgSO 3 6H 2 O, etc.
Anhydrous sulfites, when heated without access to air in sealed vessels, disproportionate into sulfides and sulfates, when heated in a stream of N 2 they lose SO 2, and when heated in air, they are easily oxidized to sulfates. With SO 2 in the aquatic environment, medium sulfites form hydrosulfites. Sulfites are relatively strong reducing agents; they are oxidized in solutions with chlorine, bromine, H 2 O 2, etc. to sulfates. They are decomposed by strong acids (for example, HC1) with the release of SO 2.
Crystalline hydrosulfites are known for K, Rb, Cs, NH 4 + , they are unstable. Other hydrosulfites exist only in aqueous solutions. Density NH 4 HSO 3 2.03 g/cm 3 ; solubility in water (g per 100 g): NH 4 HSO 3 71.8 (0 ° C), KHSO 3 49 (20 ° C).
When crystalline hydrosulfites Na or K are heated, or when the slurry solution of the pulp M 2 SO 3 is saturated with SO 2, pyrosulfites (obsolete - metabisulfites) M 2 S 2 O 5 are formed - salts of pyrosulfurous acid unknown in the free state H 2 S 2 O 5; crystals, unstable; density (g / cm 3): Na 2 S 2 O 5 1.48, K 2 S 2 O 5 2.34; above ~ 160 °С they decompose with the release of SO 2; dissolve in water (with decomposition to HSO 3 -), solubility (g per 100 g): Na 2 S 2 O 5 64.4, K 2 S 2 O 5 44.7; form hydrates Na 2 S 2 O 5 7H 2 O and ZK 2 S 2 O 5 2H 2 O; reducing agents.
Medium alkali metal sulfites are obtained by reacting an aqueous solution of M 2 CO 3 (or MOH) with SO 2 , and MSO 3 by passing SO 2 through an aqueous suspension of MCO 3 ; mainly SO 2 is used from the off-gases of contact sulfuric acid production. Sulfites are used in bleaching, dyeing and printing of fabrics, fibers, leather for grain conservation, green fodder, industrial feed waste (NaHSO 3 ,
Na 2 S 2 O 5). CaSO 3 and Ca(HSO 3) 2 - disinfectants in winemaking and sugar industry. NaНSO 3 , MgSO 3 , NH 4 НSO 3 - components of sulfite liquor during pulping; (NH 4) 2 SO 3 - SO 2 absorber; NaHSO 3 is an H 2 S absorber from production waste gases, a reducing agent in the production of sulfur dyes. K 2 S 2 O 5 - component of acid fixers in photography, antioxidant, antiseptic.
Mixture separation methods
Filtration, separation of inhomogeneous systems liquid - solid particles (suspensions) and gas - solid particles using porous filter partitions (FP) that allow liquid or gas to pass through, but retain solid particles. The driving force of the process is the pressure difference on both sides of the FP.
When separating suspensions, solid particles usually form a layer of wet sediment on the FP, which, if necessary, is washed with water or other liquid, and also dehydrated by blowing air or other gas through it. Filtration is carried out at a constant pressure difference or at a constant process speed w(the amount of filtrate in m 3 passing through 1 m 2 of the FP surface per unit time). At a constant pressure difference, the suspension is fed to the filter under vacuum or overpressure, as well as by a piston pump; when using a centrifugal pump, the pressure difference increases and the process speed decreases.
Depending on the concentration of suspensions, several types of filtration are distinguished. At a concentration of more than 1%, filtration occurs with the formation of a precipitate, and at a concentration of less than 0.1%, with clogging of the pores of the FP (clarification of liquids). If a sufficiently dense sediment layer is not formed on the FP and solid particles get into the filtrate, it is filtered using finely dispersed auxiliary materials (diatomite, perlite), which are previously applied to the FP or added to the suspension. At an initial concentration of less than 10%, partial separation and thickening of suspensions is possible.
A distinction is made between continuous and intermittent filters. For the latter, the main stages of work are filtration, washing of the sediment, its dehydration and unloading. At the same time, optimization is applicable according to the criteria of the highest productivity and the lowest costs. If washing and dehydration are not performed, and the hydraulic resistance of the partition can be neglected, then the highest productivity is achieved when the filtration time is equal to the duration of the auxiliary operations.
Applicable flexible FP made of cotton, wool, synthetic and glass fabrics, as well as non-woven FP made of natural and synthetic fibers and inflexible - ceramic, cermet and foam plastic. The directions of movement of the filtrate and the action of gravity can be opposite, coincide or be mutually perpendicular.
Filter designs are varied. One of the most common is a rotating drum vacuum filter. (cm. Fig.) of continuous action, in which the directions of movement of the filtrate and the action of gravity are opposite. The switchgear section connects zones I and II to a vacuum source and zones III and IV to a compressed air source. The filtrate and wash liquid from zones I and II enter separate receivers. The automated intermittent filter press with horizontal chambers, filter cloth in the form of an endless belt and elastic membranes for sludge dewatering by pressing has also become widespread. It performs alternating operations of filling the chambers with a suspension, filtering, washing and dehydrating the sediment, separating adjacent chambers and removing the sediment.
Definition salts within the framework of the theory of dissociation. Salts are usually divided into three groups: medium, sour and basic. In medium salts, all hydrogen atoms of the corresponding acid are replaced by metal atoms, in acid salts they are only partially replaced, in basic salts of the OH group of the corresponding base they are partially replaced by acid residues.
There are also some other types of salts, such as double salts, which contain two different cations and one anion: CaCO 3 MgCO 3 (dolomite), KCl NaCl (sylvinite), KAl (SO 4) 2 (potassium alum); mixed salts, which contain one cation and two different anions: CaOCl 2 (or Ca(OCl)Cl); complex salts, which include complex ion, consisting of a central atom linked to several ligands: K 4 (yellow blood salt), K 3 (red blood salt), Na, Cl; hydrated salts(crystal hydrates), which contain molecules water of crystallization: CuSO 4 5H 2 O (copper sulfate), Na 2 SO 4 10H 2 O (Glauber's salt).
The name of the salts is formed from the name of the anion followed by the name of the cation.
For salts of oxygen-free acids, a suffix is added to the name of the non-metal id, e.g. sodium chloride NaCl, iron(H) sulfide FeS, etc.
When naming salts of oxygen-containing acids, in the case of higher oxidation states, the ending is added to the Latin root of the name of the element — am, in the case of lower oxidation states, the ending -it. In the names of some acids, the prefix is used to designate the lowest oxidation states of a non-metal hypo-, for salts of perchloric and permanganic acids, use the prefix per-, ex: calcium carbonate CaCO 3, iron (III) sulfate Fe 2 (SO 4) 3, iron (II) sulfite FeSO 3, potassium hypochlorite KOSl, potassium chlorite KOSl 2, potassium chlorate KOSl 3, potassium perchlorate KOSl 4, potassium permanganate KMnO 4, potassium dichromate K 2 Cr 2 O 7 .
Acid and basic salts can be considered as a product of incomplete conversion of acids and bases. According to the international nomenclature, the hydrogen atom, which is part of the acid salt, is denoted by the prefix hydro-, OH group - prefix hydroxy, NaHS - sodium hydrosulfide, NaHSO 3 - sodium hydrosulfite, Mg (OH) Cl - magnesium hydroxychloride, Al (OH) 2 Cl - aluminum dihydroxy chloride.
In the names of complex ions, ligands are first indicated, followed by the name of the metal, indicating the corresponding oxidation state (Roman numerals in brackets). In the names of complex cations, Russian names of metals are used, for example: Cl 2 - tetraammine copper (P) chloride, 2 SO 4 - diammine silver (1) sulfate. In the names of complex anions, the Latin names of metals with the suffix -at are used, for example: K[Al(OH) 4 ] - potassium tetrahydroxyaluminate, Na - sodium tetrahydroxychromate, K 4 - potassium hexacyanoferrate (H) .
Names of hydrated salts (crystalline hydrates) are formed in two ways. You can use the complex cation naming system described above; for example, copper sulfate SO 4 H 2 0 (or CuSO 4 5H 2 O) can be called tetraaquacopper(II) sulfate. However, for the most well-known hydrated salts, most often the number of water molecules (the degree of hydration) is indicated by a numerical prefix to the word "hydrate", for example: CuSO 4 5H 2 O - copper (I) sulfate pentahydrate, Na 2 SO 4 10H 2 O - sodium sulfate decahydrate, CaCl 2 2H 2 O - calcium chloride dihydrate.
Solubility of salts
According to their solubility in water, salts are divided into soluble (P), insoluble (H) and slightly soluble (M). To determine the solubility of salts, use the table of the solubility of acids, bases and salts in water. If there is no table at hand, then you can use the rules. They are easy to remember.
1. All salts of nitric acid are soluble - nitrates.
2. All salts of hydrochloric acid are soluble - chlorides, except for AgCl (H), PbCl 2 (M).
3. All salts of sulfuric acid - sulfates are soluble, except for BaSO 4 (H), PbSO 4 (H).
4. Sodium and potassium salts are soluble.
5. All phosphates, carbonates, silicates and sulfides do not dissolve, except for Na salts + and K + .
Of all chemical compounds, salts are the most numerous class of substances. These are solids, they differ from each other in color and solubility in water. At the beginning of the XIX century. Swedish chemist I. Berzelius formulated the definition of salts as reaction products of acids with bases or compounds obtained by replacing hydrogen atoms in an acid with a metal. On this basis, salts are distinguished as medium, acidic and basic. Medium, or normal, salts are products of the complete replacement of hydrogen atoms in an acid with a metal.
For example:
Na 2 CO 3 - sodium carbonate;
CuSO 4 - copper (II) sulfate, etc.
Such salts dissociate into metal cations and anions of the acid residue:
Na 2 CO 3 \u003d 2Na + + CO 2 -
Acid salts are products of incomplete replacement of hydrogen atoms in an acid by a metal. Acid salts include, for example, baking soda NaHCO 3 , which consists of a metal cation Na + and an acidic singly charged residue HCO 3 - . For an acidic calcium salt, the formula is written as follows: Ca (HCO 3) 2. The names of these salts are made up of the names of medium salts with the addition of the prefix hydro- , for example:
Mg (HSO 4) 2 - magnesium hydrosulfate.
Dissociate acid salts as follows:
NaHCO 3 \u003d Na + + HCO 3 -
Mg (HSO 4) 2 \u003d Mg 2+ + 2HSO 4 -
Basic salts are products of incomplete substitution of hydroxo groups in the base for an acid residue. For example, such salts include the famous malachite (CuOH) 2 CO 3, which you read about in the works of P. Bazhov. It consists of two basic cations CuOH + and a doubly charged anion of the acid residue CO 3 2- . The CuOH + cation has a +1 charge, therefore, in the molecule, two such cations and one doubly charged CO 3 2- anion are combined into an electrically neutral salt.
The names of such salts will be the same as for normal salts, but with the addition of the prefix hydroxo-, (CuOH) 2 CO 3 - copper (II) hydroxocarbonate or AlOHCl 2 - aluminum hydroxochloride. Most basic salts are insoluble or sparingly soluble.
The latter dissociate like this:
AlOHCl 2 \u003d AlOH 2 + + 2Cl -
Salt properties
The first two exchange reactions have been discussed in detail previously.
The third reaction is also an exchange reaction. It flows between salt solutions and is accompanied by the formation of a precipitate, for example:
The fourth reaction of salts is associated with the position of the metal in the electrochemical series of metal voltages (see "Electrochemical series of metal voltages"). Each metal displaces from salt solutions all other metals located to the right of it in a series of voltages. This is subject to the following conditions:
1) both salts (both reacting and formed as a result of the reaction) must be soluble;
2) metals should not interact with water, therefore, metals of the main subgroups of groups I and II (for the latter, starting with Ca) do not displace other metals from salt solutions.
Methods for obtaining salts
Methods for obtaining and chemical properties of salts. Salts can be obtained from inorganic compounds of almost any class. Along with these methods, salts of anoxic acids can be obtained by direct interaction of a metal and a non-metal (Cl, S, etc.).
Many salts are stable when heated. However, ammonium salts, as well as some salts of low-active metals, weak acids and acids in which elements exhibit higher or lower oxidation states, decompose when heated.
CaCO 3 \u003d CaO + CO 2
2Ag 2 CO 3 \u003d 4Ag + 2CO 2 + O 2
NH 4 Cl \u003d NH 3 + HCl
2KNO 3 \u003d 2KNO 2 + O 2
2FeSO 4 \u003d Fe 2 O 3 + SO 2 + SO 3
4FeSO 4 \u003d 2Fe 2 O 3 + 4SO 2 + O 2
2Cu(NO 3) 2 \u003d 2CuO + 4NO 2 + O 2
2AgNO 3 \u003d 2Ag + 2NO 2 + O 2
NH 4 NO 3 \u003d N 2 O + 2H 2 O
(NH 4) 2 Cr 2 O 7 \u003d Cr 2 O 3 + N 2 + 4H 2 O
2KSlO 3 \u003d MnO 2 \u003d 2KCl + 3O 2
4KClO 3 \u003d 3KSlO 4 + KCl
In order to answer the question of what salt is, you usually don’t have to think for a long time. This chemical compound is quite common in everyday life. There is no need to talk about ordinary table salt. The detailed internal structure of salts and their compounds is studied by inorganic chemistry.
Salt definition
A clear answer to the question of what salt is can be found in the works of M. V. Lomonosov. He gave this name to fragile bodies that can dissolve in water and do not ignite under the influence of high temperatures or open flames. Later, the definition was derived not from their physical, but from the chemical properties of these substances.
An example of a mixed one is the calcium salt of hydrochloric and hypochlorous acid: CaOCl 2.
Nomenclature
Salts formed by metals with variable valency have an additional designation: after the formula, the valency is written in brackets in Roman numerals. So, there is iron sulfate FeSO 4 (II) and Fe 2 (SO4) 3 (III). In the name of salts there is a prefix hydro-, if there are unsubstituted hydrogen atoms in its composition. For example, potassium hydrogen phosphate has the formula K 2 HPO 4 .
Properties of salts in electrolytes
The theory of electrolytic dissociation gives its own interpretation of chemical properties. In the light of this theory, a salt can be defined as a weak electrolyte that, when dissolved, dissociates (breaks down) in water. Thus, a salt solution can be represented as a complex of positive negative ions, and the first ones are not H + hydrogen atoms, and the second ones are not OH - hydroxo group atoms. There are no ions that would be present in all types of salt solutions, so they do not have any common properties. The lower the charges of the ions that form the salt solution, the better they dissociate, the better the electrical conductivity of such a liquid mixture.
Acid salt solutions
Acid salts in solution decompose into complex negative ions, which are an acid residue, and simple anions, which are positively charged metal particles.
For example, the dissolution reaction of sodium bicarbonate leads to the decomposition of the salt into sodium ions and the rest of HCO 3 -.
The full formula looks like this: NaHCO 3 \u003d Na + + HCO 3 -, HCO 3 - \u003d H + + CO 3 2-.
Solutions of basic salts
The dissociation of basic salts leads to the formation of acid anions and complex cations consisting of metals and hydroxogroups. These complex cations, in turn, are also able to decompose in the process of dissociation. Therefore, in any solution of a salt of the main group, there are OH - ions. For example, the dissociation of hydroxomagnesium chloride proceeds as follows:
Distribution of salts
What is salt? This element is one of the most common chemical compounds. Everyone knows table salt, chalk (calcium carbonate) and so on. Among the carbonate salts, the most common is calcium carbonate. It is an integral part of marble, limestone, dolomite. And calcium carbonate is the basis for the formation of pearls and corals. This chemical compound is essential for the formation of hard integuments in insects and skeletons in chordates.
Salt has been known to us since childhood. Doctors warn against its excessive use, but in moderation it is essential for the implementation of vital processes in the body. And it is needed to maintain the correct composition of the blood and the production of gastric juice. Saline solutions, an integral part of injections and droppers, are nothing more than a solution of table salt.
Salts are the product of substitution of hydrogen atoms in an acid for a metal. Soluble salts in soda dissociate into a metal cation and an acid residue anion. Salts are divided into:
Medium
Basic
Complex
Double
Mixed
Medium salts. These are products of the complete replacement of hydrogen atoms in an acid with metal atoms, or with a group of atoms (NH 4 +): MgSO 4, Na 2 SO 4, NH 4 Cl, Al 2 (SO 4) 3.
The names of middle salts come from the names of metals and acids: CuSO 4 - copper sulfate, Na 3 PO 4 - sodium phosphate, NaNO 2 - sodium nitrite, NaClO - sodium hypochlorite, NaClO 2 - sodium chlorite, NaClO 3 - sodium chlorate, NaClO 4 - sodium perchlorate, CuI - copper (I) iodide, CaF 2 - calcium fluoride. You also need to remember a few trivial names: NaCl-table salt, KNO3-potassium nitrate, K2CO3-potash, Na2CO3-soda ash, Na2CO3∙10H2O-crystalline soda, CuSO4-copper sulfate,Na 2 B 4 O 7 . 10H 2 O- borax, Na 2 SO 4 . 10H 2 O-Glauber's salt. Double salts. it salt containing two types of cations (hydrogen atoms multibasic acids are replaced by two different cations): MgNH 4 PO 4 , KAl (SO 4 ) 2 , NaKSO 4 .Double salts as individual compounds exist only in crystalline form. When dissolved in water, they are completelydissociate into metal ions and acid residues (if the salts are soluble), for example:
NaKSO 4 ↔ Na + + K + + SO 4 2-
It is noteworthy that the dissociation of double salts in aqueous solutions takes place in 1 step. To name salts of this type, you need to know the names of the anion and two cations: MgNH4PO4 - magnesium ammonium phosphate.
complex salts.These are particles (neutral molecules orions ), which are formed as a result of joining this ion (or atom) ), called complexing agent, neutral molecules or other ions called ligands. Complex salts are divided into:
1) Cation complexes
Cl 2 - tetraamminzinc(II) dichloride
Cl2- di hexaamminecobalt(II) chloride
2) Anion complexes
K2- potassium tetrafluoroberyllate(II)
Li-lithium tetrahydridoaluminate(III)
K3-potassium hexacyanoferrate(III)
The theory of the structure of complex compounds was developed by the Swiss chemist A. Werner.
Acid salts are products of incomplete substitution of hydrogen atoms in polybasic acids for metal cations.
For example: NaHCO3
Chemical properties:
React with metals in the voltage series to the left of hydrogen.
2KHSO 4 + Mg → H 2 + Mg (SO) 4 + K 2 (SO) 4
Note that for such reactions it is dangerous to take alkali metals, because they will first react with water with a large release of energy, and an explosion will occur, since all reactions occur in solutions.
2NaHCO 3 + Fe → H 2 + Na 2 CO 3 + Fe 2 (CO 3) 3 ↓
Acid salts react with alkali solutions to form the middle salt(s) and water:
NaHCO 3 +NaOH→Na 2 CO 3 +H 2 O
2KHSO 4 +2NaOH→2H 2 O+K 2 SO 4 +Na 2 SO 4
Acid salts react with solutions of medium salts if gas is released, a precipitate forms, or water is released:
2KHSO 4 + MgCO 3 → MgSO 4 + K 2 SO 4 + CO 2 + H 2 O
2KHSO 4 +BaCl 2 →BaSO 4 ↓+K 2 SO 4 +2HCl
Acid salts react with acids if the acid product of the reaction is weaker or more volatile than the one added.
NaHCO 3 +HCl→NaCl+CO 2 +H 2 O
Acid salts react with basic oxides with the release of water and intermediate salts:
2NaHCO 3 + MgO → MgCO 3 ↓ + Na 2 CO 3 + H 2 O
2KHSO 4 + BeO → BeSO 4 + K 2 SO 4 + H 2 O
Acid salts (in particular hydrocarbonates) decompose under the influence of temperature:
2NaHCO 3 → Na 2 CO 3 + CO 2 + H 2 O
Receipt:
Acid salts are formed when alkali is exposed to an excess of a solution of a polybasic acid (neutralization reaction):
NaOH + H 2 SO 4 → NaHSO 4 + H 2 O
Mg (OH) 2 + 2H 2 SO 4 → Mg (HSO 4) 2 + 2H 2 O
Acid salts are formed by dissolving basic oxides in polybasic acids:
MgO + 2H 2 SO 4 → Mg (HSO 4) 2 + H 2 O
Acid salts are formed when metals are dissolved in an excess of a polybasic acid solution:
Mg + 2H 2 SO 4 → Mg (HSO 4) 2 + H 2
Acid salts are formed as a result of the interaction of the average salt and the acid, which formed the anion of the average salt:
Ca 3 (PO 4) 2 + H 3 PO 4 → 3CaHPO 4
Basic salts:
Basic salts are the product of incomplete substitution of the hydroxo group in the molecules of polyacid bases for acid residues.
Example: MgOHNO 3 ,FeOHCl.
Chemical properties:
Basic salts react with excess acid to form a medium salt and water.
MgOHNO 3 + HNO 3 → Mg (NO 3) 2 + H 2 O
Basic salts are decomposed by temperature:
2 CO 3 →2CuO + CO 2 + H 2 O
Obtaining basic salts:
The interaction of salts of weak acids with medium salts:
2MgCl 2 + 2Na 2 CO 3 + H 2 O → 2 CO 3 + CO 2 + 4NaCl
Hydrolysis of salts formed by a weak base and a strong acid:
ZnCl 2 + H 2 O → Cl + HCl
Most basic salts are sparingly soluble. Many of them are minerals, for example malachite Cu 2 CO 3 (OH) 2 and hydroxylapatite Ca 5 (PO 4) 3 OH.
The properties of mixed salts are not covered in the school chemistry course, but it is important to know the definition.
Mixed salts are salts in which acidic residues of two different acids are attached to one metal cation.
A good example is Ca(OCl)Cl bleach (bleach).
Nomenclature:
1. Salt contains a complex cation
First, the cation is named, then the ligands-anions entering the inner sphere, ending in "o" ( Cl - - chloro, OH - -hydroxo), then ligands, which are neutral molecules ( NH 3 -amine, H 2 O -aquo). If there are more than 1 identical ligands, their number is denoted by Greek numerals: 1 - mono, 2 - di, 3 - three, 4 - tetra, 5 - penta, 6 - hexa, 7 - hepta, 8 - octa, 9 - nona, 10 - deca. The latter is called the complexing ion, indicating its valency in brackets, if it is variable.
[ Ag (NH 3 ) 2 ](OH )-silver diamine hydroxide ( I)
[ Co (NH 3 ) 4 Cl 2 ] Cl 2 -chloride dichloro o cobalt tetraamine ( III)
2. Salt contains a complex anion.
First, the anion ligands are named, then the neutral molecules entering the inner sphere ending in "o", indicating their number with Greek numerals. The latter is called the complexing ion in Latin, with the suffix "at", indicating the valency in brackets. Next, the name of the cation located in the outer sphere is written, the number of cations is not indicated.
K 4 -hexacyanoferrate (II) potassium (reagent for Fe 3+ ions)
K 3 - potassium hexacyanoferrate (III) (reagent for Fe 2+ ions)
Na 2 -sodium tetrahydroxozincate
Most complexing ions are metals. The greatest tendency to complex formation is shown by d elements. Around the central complexing ion there are oppositely charged ions or neutral molecules - ligands or addends.
The complexing ion and ligands make up the inner sphere of the complex (in square brackets), the number of ligands coordinating around the central ion is called the coordination number.
Ions that do not enter the inner sphere form the outer sphere. If the complex ion is a cation, then there are anions in the outer sphere and vice versa, if the complex ion is an anion, then there are cations in the outer sphere. Cations are usually alkali and alkaline earth metal ions, ammonium cation. When dissociated, complex compounds give complex complex ions, which are quite stable in solutions:
K 3 ↔3K + + 3-
If we are talking about acid salts, then when reading the formula, the prefix hydro- is pronounced, for example:
Sodium hydrosulfide NaHS
Sodium bicarbonate NaHCO 3
With basic salts, the prefix is \u200b\u200bused hydroxo- or dihydroxo-
(depends on the degree of oxidation of the metal in the salt), for example:
magnesium hydroxochlorideMg(OH)Cl, aluminum dihydroxochloride Al(OH) 2 Cl
Methods for obtaining salts:
1. Direct interaction of metal with non-metal . In this way, salts of anoxic acids can be obtained.
Zn+Cl 2 →ZnCl 2
2. Reaction between acid and base (neutralization reaction). Reactions of this type are of great practical importance (qualitative reactions to most cations), they are always accompanied by the release of water:
NaOH+HCl→NaCl+H 2 O
Ba(OH) 2 + H 2 SO 4 → BaSO 4 ↓ + 2H 2 O
3. The interaction of the basic oxide with the acid :
SO 3 +BaO→BaSO 4 ↓
4. Reaction of acid oxide and base :
2NaOH + 2NO 2 → NaNO 3 + NaNO 2 + H 2 O
NaOH + CO 2 →Na 2 CO 3 +H 2 O
5. Interaction of basic oxide and acid :
Na 2 O + 2HCl → 2NaCl + H 2 O
CuO + 2HNO 3 \u003d Cu (NO 3) 2 + H 2 O
6. Direct interaction of metal with acid. This reaction may be accompanied by the evolution of hydrogen. Whether hydrogen will be released or not depends on the activity of the metal, the chemical properties of the acid and its concentration (see Properties of concentrated sulfuric and nitric acids).
Zn + 2HCl \u003d ZnCl 2 + H 2
H 2 SO 4 + Zn \u003d ZnSO 4 + H 2
7. Reaction of salt with acid . This reaction will occur provided that the acid forming the salt is weaker or more volatile than the acid that reacted:
Na 2 CO 3 + 2HNO 3 \u003d 2NaNO 3 + CO 2 + H 2 O
8. Reaction of salt with acidic oxide. Reactions occur only when heated, therefore, the reacting oxide must be less volatile than the one formed after the reaction:
CaCO 3 + SiO 2 \u003d CaSiO 3 + CO 2
9. The interaction of a non-metal with an alkali . Halogens, sulfur and some other elements, interacting with alkalis, give oxygen-free and oxygen-containing salts:
Cl 2 + 2KOH \u003d KCl + KClO + H 2 O (the reaction proceeds without heating)
Cl 2 + 6KOH \u003d 5KCl + KClO 3 + 3H 2 O (the reaction proceeds with heating)
3S + 6NaOH \u003d 2Na 2 S + Na 2 SO 3 + 3H 2 O
10. interaction between two salts. This is the most common way to obtain salts. For this, both salts that have entered into the reaction must be highly soluble, and since this is an ion exchange reaction, in order for it to go to the end, one of the reaction products must be insoluble:
Na 2 CO 3 + CaCl 2 \u003d 2NaCl + CaCO 3 ↓
Na 2 SO 4 + BaCl 2 \u003d 2NaCl + BaSO 4 ↓
11. Interaction between salt and metal . The reaction proceeds if the metal is in the voltage series of metals to the left of that contained in the salt:
Zn + CuSO 4 \u003d ZnSO 4 + Cu ↓
12. Thermal decomposition of salts . When some oxygen-containing salts are heated, new ones are formed, with a lower oxygen content, or not containing it at all:
2KNO 3 → 2KNO 2 + O 2
4KClO 3 → 3KClO 4 +KCl
2KClO 3 → 3O 2 +2KCl
13. Interaction of non-metal with salt. Some non-metals are able to combine with salts to form new salts:
Cl 2 +2KI=2KCl+I 2 ↓
14. Reaction of base with salt . Since this is an ion exchange reaction, in order for it to go to the end, it is necessary that 1 of the reaction products be insoluble (this reaction is also used to convert acid salts into medium ones):
FeCl 3 + 3NaOH \u003d Fe (OH) 3 ↓ + 3NaCl
NaOH+ZnCl 2 = (ZnOH)Cl+NaCl
KHSO 4 + KOH \u003d K 2 SO 4 + H 2 O
In the same way, double salts can be obtained:
NaOH + KHSO 4 \u003d KNaSO 4 + H 2 O
15. The interaction of metal with alkali. Metals that are amphoteric react with alkalis, forming complexes:
2Al+2NaOH+6H 2 O=2Na+3H 2
16. Interaction salts (oxides, hydroxides, metals) with ligands:
2Al+2NaOH+6H 2 O=2Na+3H 2
AgCl+3NH 4 OH=OH+NH 4 Cl+2H 2 O
3K 4 + 4FeCl 3 \u003d Fe 3 3 + 12KCl
AgCl+2NH 4 OH=Cl+2H 2 O
Editor: Kharlamova Galina Nikolaevna
SALT, a class of chemical compounds. A generally accepted definition of the concept of “Salts”, as well as the terms “acids and bases”, the products of the interaction of which salts are, currently does not exist. Salts can be considered as products of substitution of acid hydrogen protons for metal ions, NH 4 + , CH 3 NH 3 + and other cations or base OH groups for acid anions (eg, Cl - , SO 4 2-).
Classification
The products of complete substitution are medium salts, for example. Na 2 SO 4 , MgCl 2 , partially acidic or basic salts, for example KHSO 4 , СuСlOH. There are also simple salts, including one type of cations and one type of anions (for example, NaCl), double salts containing two types of cations (for example, KAl (SO 4) 2 12H 2 O), mixed salts, which include two types of acid residues ( e.g. AgClBr). Complex salts contain complex ions such as K 4 .
Physical Properties
Typical salts are crystalline substances with an ionic structure, such as CsF. There are also covalent salts, such as AlCl 3 . In fact, the nature of the chemical bond v of many salts is mixed.
By solubility in water, soluble, slightly soluble and practically insoluble salts are distinguished. Soluble include almost all salts of sodium, potassium and ammonium, many nitrates, acetates and chlorides, with the exception of salts of polyvalent metals that hydrolyze in water, many acidic salts.
Solubility of salts in water at room temperature
| Cations | Anions | |||||||||
| F- | Cl- | br- | I- | S2- | NO 3 - | CO 3 2- | SiO 3 2- | SO 4 2- | PO 4 3- | |
| Na+ | R | R | R | R | R | R | R | R | R | R |
| K+ | R | R | R | R | R | R | R | R | R | R |
| NH4+ | R | R | R | R | R | R | R | R | R | R |
| Mg2+ | RK | R | R | R | M | R | H | RK | R | RK |
| Ca2+ | NK | R | R | R | M | R | H | RK | M | RK |
| Sr2+ | NK | R | R | R | R | R | H | RK | RK | RK |
| Ba 2+ | RK | R | R | R | R | R | H | RK | NK | RK |
| sn 2+ | R | R | R | M | RK | R | H | H | R | H |
| Pb 2+ | H | M | M | M | RK | R | H | H | H | H |
| Al 3+ | M | R | R | R | G | R | G | NK | R | RK |
| Cr3+ | R | R | R | R | G | R | G | H | R | RK |
| Mn2+ | R | R | R | R | H | R | H | H | R | H |
| Fe2+ | M | R | R | R | H | R | H | H | R | H |
| Fe3+ | R | R | R | - | - | R | G | H | R | RK |
| Co2+ | M | R | R | R | H | R | H | H | R | H |
| Ni2+ | M | R | R | R | RK | R | H | H | R | H |
| Cu2+ | M | R | R | - | H | R | G | H | R | H |
| Zn2+ | M | R | R | R | RK | R | H | H | R | H |
| CD 2+ | R | R | R | R | RK | R | H | H | R | H |
| Hg2+ | R | R | M | NK | NK | R | H | H | R | H |
| Hg 2 2+ | R | NK | NK | NK | RK | R | H | H | M | H |
| Ag+ | R | NK | NK | NK | NK | R | H | H | M | H |
Legend:
P - the substance is highly soluble in water; M - slightly soluble; H - practically insoluble in water, but easily soluble in weak or dilute acids; RK - insoluble in water and soluble only in strong inorganic acids; NK - insoluble neither in water nor in acids; G - completely hydrolyzes upon dissolution and does not exist in contact with water. A dash means that such a substance does not exist at all.
In aqueous solutions, salts completely or partially dissociate into ions. Salts of weak acids and/or weak bases undergo hydrolysis. Aqueous salt solutions contain hydrated ions, ion pairs, and more complex chemical forms, including hydrolysis products, etc. A number of salts are also soluble in alcohols, acetone, acid amides, and other organic solvents.
From aqueous solutions, salts can crystallize in the form of crystalline hydrates, from non-aqueous solutions - in the form of crystalline solvates, for example CaBr 2 3C 2 H 5 OH.
Data on various processes occurring in water-salt systems, on the solubility of salts in their joint presence depending on temperature, pressure and concentration, on the composition of solid and liquid phases can be obtained by studying the solubility diagrams of water-salt systems.
General methods for the synthesis of salts.
1. Obtaining medium salts:
1) metal with non-metal: 2Na + Cl 2 = 2NaCl
2) metal with acid: Zn + 2HCl = ZnCl 2 + H 2
3) metal with a salt solution of a less active metal Fe + CuSO 4 = FeSO 4 + Cu
4) basic oxide with acid oxide: MgO + CO 2 = MgCO 3
5) basic oxide with acid CuO + H 2 SO 4 \u003d CuSO 4 + H 2 O
6) bases with acidic oxide Ba (OH) 2 + CO 2 = BaCO 3 + H 2 O
7) bases with acid: Ca (OH) 2 + 2HCl \u003d CaCl 2 + 2H 2 O
8) acid salts: MgCO 3 + 2HCl = MgCl 2 + H 2 O + CO 2
BaCl 2 + H 2 SO 4 \u003d BaSO 4 + 2HCl
9) a base solution with a salt solution: Ba (OH) 2 + Na 2 SO 4 \u003d 2NaOH + BaSO 4
10) solutions of two salts 3CaCl 2 + 2Na 3 PO 4 = Ca 3 (PO 4) 2 + 6NaCl
2. Obtaining acid salts:
1. Interaction of an acid with a lack of a base. KOH + H 2 SO 4 \u003d KHSO 4 + H 2 O
2. Interaction of a base with an excess of acid oxide
Ca(OH) 2 + 2CO 2 = Ca(HCO 3) 2
3. Interaction of an average salt with acid Ca 3 (PO 4) 2 + 4H 3 PO 4 \u003d 3Ca (H 2 PO 4) 2
3. Obtaining basic salts:
1. Hydrolysis of salts formed by a weak base and a strong acid
ZnCl 2 + H 2 O \u003d Cl + HCl
2. Addition (drop by drop) of small amounts of alkalis to solutions of medium metal salts AlCl 3 + 2NaOH = Cl + 2NaCl
3. Interaction of salts of weak acids with medium salts
2MgCl 2 + 2Na 2 CO 3 + H 2 O \u003d 2 CO 3 + CO 2 + 4NaCl
4. Obtaining complex salts:
1. Reactions of salts with ligands: AgCl + 2NH 3 = Cl
FeCl 3 + 6KCN] = K 3 + 3KCl
5. Getting double salts:
1. Joint crystallization of two salts:
Cr 2 (SO 4) 3 + K 2 SO 4 + 24H 2 O \u003d 2 + NaCl
4. Redox reactions due to the properties of the cation or anion. 2KMnO 4 + 16HCl = 2MnCl 2 + 2KCl + 5Cl 2 + 8H 2 O
2. Chemical properties of acid salts:
Thermal decomposition to medium salt
Ca (HCO 3) 2 \u003d CaCO 3 + CO 2 + H 2 O
Interaction with alkali. Obtaining medium salt.
Ba(HCO 3) 2 + Ba(OH) 2 = 2BaCO 3 + 2H 2 O
3. Chemical properties of basic salts:
Thermal decomposition. 2 CO 3 \u003d 2CuO + CO 2 + H 2 O
Interaction with acid: formation of an average salt.
Sn(OH)Cl + HCl = SnCl 2 + H 2 O
4. Chemical properties of complex salts:
1. Destruction of complexes due to the formation of poorly soluble compounds:
2Cl + K 2 S \u003d CuS + 2KCl + 4NH 3
2. Exchange of ligands between the outer and inner spheres.
K 2 + 6H 2 O \u003d Cl 2 + 2KCl
5. Chemical properties of double salts:
Interaction with alkali solutions: KCr(SO 4) 2 + 3KOH = Cr(OH) 3 + 2K 2 SO 4
2. Recovery: KCr (SO 4) 2 + 2H ° (Zn, diluted H 2 SO 4) \u003d 2CrSO 4 + H 2 SO 4 + K 2 SO 4
The raw materials for the industrial production of a number of chloride salts, sulfates, carbonates, Na, K, Ca, Mg borates are sea and ocean water, natural brines formed during its evaporation, and solid deposits of salts. For a group of minerals that form sedimentary salt deposits (sulfates and chlorides of Na, K and Mg), the code name “natural salts” is used. The largest deposits of potassium salts are located in Russia (Solikamsk), Canada and Germany, powerful deposits of phosphate ores - in North Africa, Russia and Kazakhstan, NaNO3 - in Chile.
Salts are used in food, chemical, metallurgical, glass, leather, textile industries, agriculture, medicine, etc.
The main types of salts
1. Borates(oxoborates), salts of boric acids: metaboric HBO 2, orthoboric H 3 BO 3 and polyboric acids not isolated in the free state. According to the number of boron atoms in the molecule, they are divided into mono-, di, tetra-, hexaborates, etc. Borates are also called according to the acids that form them and according to the number of moles of B 2 O 3 per 1 mole of the basic oxide. So various metaborates can be called monoborates if they contain an anion B (OH) 4 or a chain anion (BO 2) n n-diborates - if they contain a double chain anion (B 2 O 3 (OH) 2) n 2n-triborates - if they contain ring anion (B 3 O 6) 3-.
