Which salts are soluble in water. What is salt? Formula, properties of salt (chemistry). Formation of an ionic bond between sodium and chlorine
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 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. This 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 precipitates, 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 replacement of the hydroxo group in the molecules of polyacid bases with acidic 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 in 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 a complex ion is a cation, then there are anions in the outer sphere and vice versa, if a 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
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 acid 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
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 OH groups of the base 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-.
The solubility table of salts, acids and bases is the foundation, without which it is impossible to fully master chemical knowledge. The solubility of bases and salts helps in teaching not only schoolchildren, but also professional people. The creation of many life products cannot do without this knowledge.
Table of solubility of acids, salts and bases in water
The table of solubility of salts and bases in water is a manual that helps in mastering the basics of chemistry. The following notes will help you understand the table below.
- P - indicates a soluble substance;
- H is an insoluble substance;
- M - the substance is slightly soluble in the aquatic environment;
- RK - a substance can dissolve only when exposed to strong organic acids;
- The dash will say that such a creature does not exist in nature;
- NK - does not dissolve in either acids or water;
- ? - a question mark indicates that today there is no exact information about the dissolution of the substance.
Often, the table is used by chemists and schoolchildren, students for laboratory research, during which it is necessary to establish the conditions for the occurrence of certain reactions. According to the table, it turns out to find out how the substance behaves in a hydrochloric or acidic environment, whether a precipitate is possible. Precipitate during research and experiments indicates the irreversibility of the reaction. This is a significant point that can affect the course of the entire laboratory work.
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 valence 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.