In the previous sections, reactions in which salts are formed were constantly encountered.
Salts are substances in which metal atoms are bonded to acidic residues.
The exception is ammonium salts, in which it is not metal atoms, but NH 4 + particles that are associated with acidic residues. Examples of typical salts are given below.
NaCl – sodium chloride,
Na 2 SO 4 – sodium sulfate,
CaSO 4 – calcium sulfate,
CaCl 2 – calcium chloride,
(NH 4) 2 SO 4 – ammonium sulfate.
The formula of the salt is built taking into account the valencies of the metal and the acid residue. Almost all salts are ionic compounds, so we can say that in salts metal ions and ions of acidic residues are interconnected:
Na + Cl – – sodium chloride
Ca 2+ SO 4 2– – calcium sulfate, etc.
The names of salts are made up of the name of the acid residue and the name of the metal. The main thing in the name is the acid residue. The names of salts depending on the acid residue are shown in Table 4.6. The upper part of the table shows oxygen-containing acidic residues, and the lower part shows oxygen-free residues.
Table 4-6. Construction of names of salts.
|
Salt of which acid |
Acid residue |
Valency of the residue |
Name of salts | |
|
Nitrogen HNO 3 |
Ca(NO 3)2 calcium nitrate |
|||
|
Silicon H 2 SiO 3 |
silicates |
Na 2 SiO 3 sodium silicate |
||
|
Sulfuric H2SO4 |
sulfates |
PbSO 4 lead sulfate |
||
|
Coal H2CO3 |
carbonates |
Na 2 CO 3 sodium carbonate |
||
|
Phosphorus H 3 PO 4 |
AlPO 4 aluminum phosphate |
|
Hydrogen bromide HBr |
NaBr sodium bromide |
|||
|
Hydrogen iodide HI |
KI potassium iodide |
|||
|
Hydrogen sulfide H 2 S |
sulfides |
FeS iron(II) sulfide |
||
|
Salt HCl |
NH 4 Cl ammonium chloride |
|||
|
Hydrofluoride HF |
CaF 2 calcium fluoride |
From Table 4-6 it can be seen that the names of oxygen-containing salts have the endings “ at", and the names of oxygen-free salts have the endings " eid».
In some cases, the ending "" may be used for oxygenated salts. it"For example, Na 2 SO 3 - sulfite sodium This is done in order to distinguish between salts of sulfuric acid (H 2 SO 4) and sulfurous acid (H 2 SO 3) and in other similar cases.
All salts are divided into medium, sour And basic. Average salts contain only metal atoms and an acid residue. For example, all salts from Table 4-6 are average salts.
Any salt can be obtained by an appropriate neutralization reaction. For example, sodium sulfite is formed in the reaction between sulfurous acid and base (caustic soda). In this case, for 1 mole of acid it is required to take 2 moles of base:
If you take only 1 mole of base - that is, less than is required for full neutralization, then it is formed sour salt – sodium hydrosulfite:
Sour salts are formed by polybasic acids. Monobasic acids do not form acid salts.
Acidic salts, in addition to metal ions and an acid residue, contain hydrogen ions.
The names of acid salts contain the prefix “hydro” (from the word hydrogenium - hydrogen). For example:
NaHCO 3 – sodium bicarbonate,
K 2 HPO 4 – potassium hydrogen phosphate,
KH 2 PO 4 – potassium dihydrogen phosphate.
Basic salts are formed when the base is incompletely neutralized. The names of the main salts are formed using the prefix “hydroxo”. Below is an example showing the difference between basic salts and ordinary (medium) salts:
Basic salts, in addition to metal ions and an acid residue, contain hydroxyl groups.
Basic salts are formed only from polyacid bases. Monoacid bases cannot form such salts.
Table 4.6 shows international titles salts However, it is also useful to know the Russian names and some historical, traditional names of salts that are important (Table 4.7).
Table 4.7. International, Russian and traditional names of some important salts.
|
International name |
Russian name |
Traditional name |
Application |
|
|
Sodium carbonate |
Sodium carbonate |
In everyday life - as a detergent and cleaning agent |
||
|
Sodium bicarbonate |
Sodium carbonate acid |
Baking soda |
Food product: baked confectionery |
|
|
Potassium carbonate |
Potassium carbonate |
Used in technology |
||
|
Sodium sulfate |
Sodium sulfate |
Glauber's salt |
Medicine |
|
|
Magnesium sulfate |
Magnesium sulfate |
Epsom salt |
Medicine |
|
|
Potassium chlorate |
Potassium perchloric acid |
Bertholet's salt |
Used in incendiary mixtures for match heads |
For example, in no case should you confuse soda Na 2 CO 3 and baking soda NaHCO3. If accidentally used as food soda instead of baking soda, you can get a severe chemical burn.
In chemistry and technology, many ancient names are still preserved. For example, caustic soda- not a salt at all, but the technical name for sodium hydroxide NaOH. If ordinary soda can be used to clean a sink or dishes, then under no circumstances should caustic soda be handled or used in everyday life!
The structure of salts is similar to the structure of the corresponding acids and bases. Below are the structural formulas of typical intermediate, acidic and basic salts.
Let us give the structure and name of the main salt, the formula of which is: 2 CO 3 – iron (III) dihydroxycarbonate. When considering the structural formula of such a salt, it becomes clear that this salt is the product of partial neutralization of iron (III) hydroxide with carbonic acid:
>> Chemistry: Salts, their classification and properties
Of all chemical compounds salts are the most numerous class of substances. This solids, they differ from each other in color and solubility in water.
Salts is a class of chemical compounds consisting of metal ions and acidic ions.
IN early XIX V. Swedish chemist I. Verzelius formulated the definition of salts as products of reactions of acids with bases, or compounds obtained by replacing hydrogen atoms in an acid with a metal. On this basis, salts are distinguished between medium, acidic and basic.
Average or normal- these are products of complete replacement of hydrogen atoms in an acid with a metal.
It is these salts that you are already familiar with and know their nomenclature. For example:
Na2С03 - sodium carbonate, CuSO4 - copper (II) sulfate, etc.
Such salts dissociate into metal cations and anions of the acid residue:
Acid salts - these are products of incomplete replacement of hydrogen atoms in an acid with a metal.
Acidic salts include, for example, baking soda, which consists of a metal cation and an acidic single-charge residue HCO3. For an acidic calcium salt, the formula is written as follows: Ca(HCO3)2.
The names of these salts are composed of the names of the salts with the addition of the word hydro, for example:
Basic salts- these are products of incomplete substitution of hydroxo groups in the base with an acid residue.
For example, such salts include the famous malachite (SiOH)2 CO3, which you read about in the tales of I. Bazhov. It consists of two main cations CuOH and a doubly charged anion of the acidic residue CO 2-3.
The CuOH+ cation has a charge of +1, so in the molecule two such cations and one doubly charged CO anion are combined into an electrically neutral salt.
The names of such salts will be the same as those of normal salts, but with the addition of the word hydroxo-, for example (CuOH)2 CO3 - copper (II) hydroxycarbonate or AlONCl2 - aluminum hydroxychloride. The vast majority of basic salts are insoluble or slightly soluble. The latter dissociate like this:
Typical salt reactions
4. Salt + metal -> another salt + another metal.
The first two exchange reactions have already been discussed in detail earlier.
The third reaction is also an exchange reaction. It flows between salt solutions and is accompanied by the formation of sediment, for example:
The fourth reaction of salts is associated with the name of the greatest Russian chemist N.N. Beketov, who in 1865 studied the ability of metals to displace other metals from salt solutions. For example, copper tu solutions of its salts can be replaced by metals such as magnesium, aluminum, Al, zinc and other metals. But copper is not replaced by mercury, silver Аg, gold Аu, since atm metals in the voltage series are located to the right than copper. But copper displaces them from salt solutions: 
N. Beketov, acting with hydrogen gas under pressure on solutions of mercury and silver salts, found that the hydrogen atom, like some other metals, displaces mercury and silver from their salts.
Arranging metals, I also hydrogen according to their ability to displace each other and salt solutions. Beketov made up the series. which he called the vegetative series of metals. Later (1802 V. Nerist) it was proven that the displacement series Veketovn practically coincides with the series in which metals and hydrogen are located (to the right) in order of decreasing their reducing ability and the molar concentration of metal ions is equal to 1 mol/l. This series is called the electrochemical stress series of metals. You have already become familiar with this series when you looked at the interaction of acids with metals and found out that metals located to the left of hydrogen interact with acid solutions. This is the first step in a series of voltages. It is fulfilled subject to a number of conditions that we talked about earlier.
The second rule of the stress series is as follows: each metal displaces from salt solutions all other metals located to the right of it in the stress series. This rule is also observed if the following conditions are met:
a) both salts (both the reacting one and those formed as a result of the reaction) must be soluble;
b) metals should not interact with water, therefore the metals of the main subgroups of groups I and II (for the latter, starting with Ca) do not displace other metals in salt solutions.
1. Salts are medium (normal), acidic and basic.
2. Dissociation of various salt groups.
3. Typical properties of normal salts: their interaction with acids, alkalis, other salts and metals.
4. Two rules for a series of metal stresses.
5. Conditions for reactions of salts with metals.
Complete the molecular equations of possible reactions occurring in solutions and write the corresponding ionic equations:
If the reaction cannot be carried out, explain why.
An excess of barium nitrate solution was added to 980 g of a 5% solution of weedy acid. Find the mass of the precipitate that fell.
Write down the reaction equations for all possible ways to obtain iron (II) sulfate.
Give the names of the salts.
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The most difficult among inorganic compounds are salts. They are very diverse in composition. They are divided into medium, sour, basic, double, complex, mixed.
Salts are compounds that form when dissociated into aqueous solution positively charged metal ions and negatively charged ions of acidic residues, and sometimes, in addition to them, hydrogen ions and hydroxide ions.
Salts can be considered as products of the replacement of hydrogen atoms in an acid with metal atoms (or groups of atoms):
H 2 SO 4 → NaHSO 4 → Na 2 SO 4,
Or as products of substitution of hydroxo groups in the basic hydroxide with acidic residues:
Zn (OH) 2 → ZnOHCl → ZnCl 2.
With complete substitution we get medium (or normal) salts:
Ca(OH) 2 + H 2 SO 4 = CaSO 4 + 2H 2 O.
When medium salts are dissolved, metal cations and anions of the acid residue are formed:
Na 2 SO 4 →2 Na + + SO 4 2 - .
When hydrogen is not completely replaced, acids are obtained acid salts:
NaOH + H 2 CO 3 = NaHCO 3 + H 2 O.
When acidic salts are dissolved in a solution, metal cations, complex anions of the acidic residue, as well as ions that are products of the dissociation of this complex residue, including H + ions, are formed:
NaHCO 3 →Na + + HCO 3 -
HCO 3 - H + + CO 3 2 - .
In case of incomplete substitution of hydroxyl groups of the base - basic salts:
Mg(OH) 2 + HBr = Mg(OH)Br + H 2 O.
When basic salts dissolve in solution, acid anions and complex cations consisting of metal and hydroxyl groups are formed. These complex cations are also capable of dissociation. Therefore, the solution of the basic salt contains OH ions - :
Mg(OH)Br → (MgOH) + + Br - ,
(MgOH) + Mg 2+ + OH - .
Thus, according to this definition, salts are divided into average e, sour And basic.
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 CaCl (OCl )) - calcium salt, hydrochloric and hypochlorous ( HOCl ) acids (calcium chloride-hypochlorite). Complex salts contain complex cations or anions: K 3 + [Fe (CN) 6] −3, K 4 + [Fe (CN) 6] −4, [Cr (H 2 O) 5 Cl] 2+ Cl 2 −.
According to modern nomenclature rules, the names of salts are formed from the name of the anion in the nominative case and the name of the cation in the genitive case. For example FeS - iron sulfide ( II), Fe 2 (SO 4 ) 3 - ferrous sulfate ( III ). The hydrogen atom that is part of an acid salt is denoted by the prefix hydro- ( NaHSO3 -sodium hydrosulfite), and the OH group - - prefix hydroxo- ( Al(OH)2Cl - aluminum dihydroxychloride).
Obtaining salts
Salts are closely related to all other classes of inorganic compounds and can be obtained from almost any class. Most of the methods for obtaining salts have already been discussed above (section ,), these include:
1. Interaction of basic, acidic and amphoteric oxides with each other:
BaO + SiO 2 = BaSiO 3,
MgO + Al 2 O 3 = Mg(AlO 2) 2,
SO 3 + Na 2 O = Na 2 SO 4,
P 2 O 5 + Al 2 O 3 = 2AlPO 4.
2. Interaction of oxides with hydroxides (with acids and bases):
ZnO + H 2 SO 4 = ZnSO 4 + H 2 O,
CO 2 + 2KOH = K 2 CO 3 + H 2 O,
2 NaOH + Al 2 O 3 = 2 NaAlO 2 + H 2 O.
3. Interaction of bases with medium and acidic salts:
CuSO 4 + 2KOH = Cu(OH) 2 ↓ + K 2 SO 4 ,
K 2 SO 4 + Ba(OH) 2 = 2KOH + BaSO 4↓ .
2NaHSO 3 + 2KOH = Na 2 SO 3 + K 2 SO 3 + 2H 2 O,
Ca(HCO 3) 2 + Ba(OH) 2 = BaCO 3↓ + CaCO 3 ↓ + 2H 2 O.
Cu(OH) 2 + 2NaHSO 4 = CuSO 4 + Na 2 SO 4 + 2H 2 O.
4. Salts of oxygen-free acids, in addition, can be obtained by direct interaction of metals and non-metals:
2 Mg + Cl 2 = MgCl 2.
Chemical properties of salts
During chemical reactions of salts, the characteristics of both cations and anions included in their composition appear. Metal cations in solutions can react with other anions to form insoluble compounds. On the other hand, the anions included in the salts can combine with cations to form precipitation or slightly dissociated compounds (or in redox reactions). Thus, salts can react:
|
1. With metals |
Cu + HgCl 2 = CuCl 2 + Hg, Zn + Pb(NO 3) 2 = Zn(NO 3) 2 + Pb. |
|
2. With acids |
Na 2 CO 3 + 2HCl = 2NaCl + H 2 O + CO 2, AgCl + HBr = AgBr ↓ + HCl |
|
3. With salts |
AgNO 3 + NaCl = AgCl ↓ + NaNO 3, K 2 CrO 4 + Pb(NO 3) 2 = KNO 3 + PbCrO 4↓ . |
|
4. With reasons |
CuSO 4 + 2NaOH = Cu(OH) 2 ↓ + Na 2 SO 4, Ni(NO 3) 2 + 2KOH = Ni(OH) 2 + 2KNO 3. |
|
5. 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 = CaO + CO 2, 2Ag 2 CO 3 = 4Ag + 2CO 2 + O 2, NH 4 Cl = NH 3 + HCl, 2KNO 3 = 2KNO 2 + O 2, 2FeSO 4 = Fe 2 O 3 + SO 2 + SO 3, 4FeSO 4 = 2Fe 2 O 3 + 4SO 2 + O 2, NH 4 NO 3 = N 2 O + 2 H 2 O. |
|
M.V. Andryukhova, L.N. Borodina
Salts can also be considered as the products of complete or partial replacement of hydrogen ions in acid molecules with metal ions (or complex positive ions, for example, ammonium ion NH) or as the product of complete or partial replacement of hydroxyl groups in basic hydroxide molecules with acidic residues. With complete substitution we get medium (normal) salts. With incomplete replacement of H + ions in acid molecules, the result is acid salts, with incomplete substitution of OH - groups in base molecules – basic salts. Examples of salt formation:
H3PO4 + 3NaOH 
Na 3 PO 4 + 3H 2 O
Na 3 PO 4 ( phosphate sodium) – medium (normal salt);
H3PO4 + NaOH 
NaH 2 PO 4 + H 2 O
NaH 2 PO 4 (dihydrogen phosphate sodium) – acidic salt;
Mq(OH) 2 + HCl 
MqOHCl + H2O
MqOHCl ( hydroxychloride magnesium) is the main salt.
Salts formed by two metals and one acid are called double salts. For example, potassium aluminum sulfate (potassium alum) KAl(SO 4) 2 *12H 2 O.
Salts formed by one metal and two acids are called mixed salts. For example, calcium chloride-hypochloride CaCl(ClO) or CaOCl 2 is a calcium salt of hydrochloric HCl and hypochlorous acids HClO.
Double and mixed salts, when dissolved in water, dissociate into all the ions that make up their molecules.
For example, KAl(SO 4) 2 
K + + Al 3+ + 2SO 
;
CaCl(ClO) 
Ca 2+ + Cl - + ClO - .
Complex salts- these are complex substances in which it is possible to isolate central atom(complexing agent) and associated molecules and ions - ligands. The central atom and ligands form complex (inner sphere), which when writing the formula of a complex compound is enclosed in square brackets. The number of ligands in the inner sphere is called coordination number. The molecules and ions surrounding the complex form outer sphere.
Central atom Ligand
K 3
Coordination number
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, for example, NaCl sodium chloride, FeS iron (II) sulfide.
When naming salts of oxygen-containing acids Latin root ending is added to the element name -at for higher oxidation states, -it for lower ones (for some acids the prefix is used hypo- for low oxidation states of non-metal; for salts of perchloric and permanganic acids the prefix is used per-). For example, CaCO 3 - calcium carbonate, Fe 2 (SO 4) 3 - iron (III) sulfate, FeSO 3 - iron (II) sulfite, KOSl - potassium hypochlorite, KClO 2 - potassium chlorite, KClO 3 - potassium chlorate, KClO 4 – potassium perchlorate, KMnO 4 - potassium permanganate, K 2 Cr 2 O 7 – potassium dichromate.
The names of complex ions include the ligands first. The name of the complex ion is completed by the name of the metal, indicating the corresponding oxidation state (in Roman numerals in parentheses). The names of complex cations use Russian names of metals, for example, [ Cu(NH 3) 4 ]Cl 2 - tetraammine copper (II) chloride. The names of complex anions use the Latin names of metals with the suffix –at, for example, K – potassium tetrahydroxoaluminate.
Chemical properties of salts
See properties of bases.
See properties of acids.
SiO 2 + CaCO 3 
CaSiO3 + CO2 
.
Amphoteric oxides (they are all non-volatile) displace volatile oxides from their salts during fusion
Al 2 O 3 + K 2 CO 3 
2KAlO 2 + CO 2 .
5. Salt 1 + salt 2 
salt 3 + salt 4.
An exchange reaction between salts occurs in solution (both salts must be soluble) only if at least one of the products is a precipitate
AqNO3 + NaCl 
AqCl 
+ NaNO3.
6. Salt of a less active metal + More active metal 
Less active metal + salt.
Exceptions - alkali and alkaline earth metals in solution primarily react with water
Fe + CuCl 2 
FeCl 2 +Cu.
7. Salt 
thermal decomposition products.
I) Salts of nitric acid. The products of thermal decomposition of nitrates depend on the position of the metal in the series of metal stresses:
a) if the metal is to the left of Mq (excluding Li): MeNO 3 
MeNO 2 + O 2 ;
b) if the metal is from Mq to Cu, as well as Li: MeNO 3 
MeO + NO 2 + O 2;
c) if the metal is to the right of Cu: MeNO 3 
Me + NO 2 + O 2.
II) Salts of carbonic acid. Almost all carbonates decompose to the corresponding metal and CO 2. Carbonates of alkali and alkaline earth metals except Li do not decompose when heated. Silver and mercury carbonates decompose to free metal
MeSO 3 
MeO + CO 2;
2Aq 2 CO 3 
4Aq + 2CO 2 + O 2 .
All hydrocarbonates decompose to the corresponding carbonate.
Me(HCO 3) 2 
MeCO 3 + CO 2 +H 2 O.
III) Ammonium salts. Many ammonium salts decompose when heated, releasing NH 3 and the corresponding acid or its decomposition products. Some ammonium salts containing oxidizing anions decompose to release N2, NO, NO2
NH4Cl 
NH 3 
+HCl 
;
NH4NO2 
N 2 +2H 2 O;
(NH 4) 2 Cr 2 O 7 
N 2 + Cr 2 O 7 + 4H 2 O.
In table 1 shows the names of acids and their average salts.
Names of the most important acids and their middle salts
|
Name |
||
|
Meta-aluminum |
Metaaluminate |
|
|
Arsenic | ||
|
Arsenic | ||
|
Metaborn |
Metaborate |
|
|
Orthoboric |
Orthoborate |
|
|
Quadruple |
Tetraborate |
|
|
Hydrobromic | ||
|
Ant | ||
|
Vinegar | ||
|
Hydrocyanic acid (hydrocyanic acid) | ||
|
Coal |
Carbonate |
|
End of table. 1
|
Name |
||
|
Sorrel | ||
|
Hydrochloric acid (hydrochloric acid) | ||
|
Hypochlorous |
Hypochlorite |
|
|
Chloride | ||
|
Chlorous | ||
|
Perchlorate |
||
|
Metachromic |
Metachromite |
|
|
Chrome | ||
|
Two-chrome |
Dichromate |
|
|
Hydroiodide | ||
|
Periodat |
||
|
Margontsovaya |
Permanganate |
|
|
Hydrogen azide (hydrogen nitrous) | ||
|
Nitrogenous | ||
|
Metaphosphoric |
Metaphosphate |
|
|
Orthophosphoric |
Orthophosphate |
|
|
Diphosphorus |
Diphosphate |
|
|
Hydrofluoric acid (hydrofluoric acid) | ||
|
Hydrogen sulfide | ||
|
Rhodane-hydrogen | ||
|
Sulphurous | ||
|
Dusulfur |
Disulfate |
|
|
Peroxo-doublesulfur |
Peroxodisulfate |
|
|
Silicon | ||
EXAMPLES OF SOLVING PROBLEMS
Task 1. Write the formulas of the following compounds: calcium carbonate, calcium carbide, magnesium hydrogen phosphate, sodium hydrosulfide, iron (III) nitrate, lithium nitride, copper (II) hydroxycarbonate, ammonium dichromate, barium bromide, potassium hexacyanoferrate (II), sodium tetrahydroxoaluminate.
Solution. Calcium carbonate – CaCO 3, calcium carbide – CaC 2, magnesium hydrogen phosphate – MqHPO 4, sodium hydrosulfide – NaHS, iron (III) nitrate – Fe(NO 3) 3, lithium nitride – Li 3 N, copper (II) hydroxycarbonate – 2 CO 3, ammonium dichromate - (NH 4) 2 Cr 2 O 7, barium bromide - BaBr 2, potassium hexacyanoferrate (II) - K 4, sodium tetrahydroxoaluminate - Na.
Task 2. Give examples of the formation of salt: a) from two simple substances; b) from two complex substances; c) from simple and complex substances.
Solution.
a) iron, when heated with sulfur, forms iron (II) sulfide:
Fe+S 
FeS;
b) salts enter into exchange reactions with each other in an aqueous solution if one of the products precipitates:
AqNO3 + NaCl 
AqCl 
+NaNO 3 ;
c) salts are formed when metals are dissolved in acids:
Zn + H2SO4 
ZnSO 4 +H 2 .
Task 3. During the decomposition of magnesium carbonate, carbon monoxide (IV) was released, which was passed through lime water (taken in excess). In this case, a precipitate weighing 2.5 g was formed. Calculate the mass of magnesium carbonate taken for the reaction.
Solution.
We compose the equations of the corresponding reactions:
MqCO3 
MqO +CO 2 ;
CO 2 + Ca(OH) 2 
CaCO 3 +H 2 O.
2. Calculate the molar masses of calcium carbonate and magnesium carbonate using the periodic table of chemical elements:
M(CaCO 3) = 40+12+16*3 = 100g/mol;
M(MqCO 3) = 24+12+16*3 = 84 g/mol.
3. Calculate the amount of calcium carbonate substance (precipitated substance):
n(CaCO 3)= 
.
From the reaction equations it follows that
n(MqCO 3)=n(CaCO 3)=0.025 mol.
We calculate the mass of calcium carbonate taken for the reaction:
m(MqCO 3)=n(MqCO 3)*M(MqCO 3)= 0.025mol*84g/mol=2.1g.
Answer: m(MqCO 3) = 2.1 g.
Task 4. Write the reaction equations that allow the following transformations to occur:
Mq 
MQSO 4 
Mq(NO 3) 2 
MqO 
(CH 3 COO) 2 Mq.
Solution.
Magnesium dissolves in dilute sulfuric acid:
Mq + H 2 SO 4 
MqSO 4 +H 2 .
Magnesium sulfate enters into an exchange reaction in an aqueous solution with barium nitrate:
MqSO 4 + Ba(NO 3) 2 
BaSO 4 +Mq(NO 3) 2.
When strongly heated, magnesium nitrate decomposes:
2Mq(NO 3) 2 
2MqO+ 4NO 2 + O 2 .
4. Magnesium oxide is the main oxide. It dissolves in acetic acid
MqO + 2CH 3 COOH 
(CH 3 COO) 2 Mq + H 2 O.
Glinka, N.L. General chemistry. / N.L. Glinka. – M.: Integral-press, 2002.
Glinka, N.L. Problems and exercises in general chemistry. / N.L. Glinka. - M.: Integral-press, 2003.
Gabrielyan, O.S. Chemistry. 11th grade: educational. for general education institutions. / O.S. Gabrielyan, G.G. Lysova. - M.: Bustard, 2002.
Akhmetov, N.S. General and inorganic chemistry. / N.S. Akhmetov. – 4th ed. - M.: graduate School, 2002.
Chemistry. Classification, nomenclature and reaction capabilities of inorganic substances: guidelines for performing practical and independent work for students of all forms of education and all specialties
When you hear the word “salt”, the first association is, of course, culinary, without which any dish will seem tasteless. But this is not the only substance that belongs to the class chemical substances salt. Examples, composition and Chemical properties you can find salts in this article, and also learn how to correctly form the name of any of them. Before we continue, let's agree that in this article we will only consider inorganic medium salts (obtained by the reaction of inorganic acids with complete replacement of hydrogen).
Definition and chemical composition
One definition of salt is:
- (i.e., consisting of two parts), which includes metal ions and an acid residue. That is, it is a substance resulting from the reaction of an acid and a hydroxide (oxide) of any metal.
There is another definition:
- This is a compound that is the product of the complete or partial replacement of hydrogen ions of an acid with metal ions (suitable for medium, basic and acidic).
Both definitions are correct, but do not reflect the whole essence of the process of obtaining salt.
Classification of salts
Considering the various representatives of the class of salts, you can see that they are:
- Oxygen-containing (salts of sulfuric, nitric, silicic and other acids, the acid residue of which includes oxygen and another non-metal).
- Oxygen-free, i.e. salts formed during a reaction whose residue does not contain oxygen - hydrochloric, hydrobromic, hydrogen sulphide and others.
By the number of substituted hydrogens:
- Monobasic: hydrochloric, nitrogen, hydrogen iodide and others. The acid contains one hydrogen ion.
- Dibasic: Two hydrogen ions are replaced by metal ions to form a salt. Examples: sulfuric, sulphurous, hydrogen sulphide and others.
- Tribasic: in the acid composition, three hydrogen ions are replaced by metal ions: phosphoric.
There are other types of classifications based on composition and properties, but we will not discuss them, since the purpose of the article is slightly different.
Learning to name correctly
Any substance has a name that is understandable only to residents of a certain region; it is also called trivial. Table salt is an example of a colloquial name; according to international nomenclature, it will be called differently. But in a conversation, absolutely any person familiar with the nomenclature of names will easily understand that we are talking about a substance with chemical formula NaCl. This salt is a derivative of hydrochloric acid, and its salts are called chlorides, that is, it is called sodium chloride. You just need to learn the names of the salts given in the table below, and then add the name of the metal that formed the salt.
But the name is so easy to formulate if the metal has a constant valence. Now let’s look at the name), which has a metal with variable valence - FeCl 3. The substance is called ferric chloride. This is exactly the right name!
| Acid formula | Acid name | Acid residue (formula) | Nomenclature name | Example and trivial name |
| HCl | salt | Cl- | chloride | NaCl (table salt, rock salt) |
| HI | hydrogen iodide | I - | iodide | NaI |
| HF | hydrogen fluoride | F- | fluoride | NaF |
| HBr | hydrobromic | Br- | bromide | NaBr |
| H2SO3 | sulfurous | SO 3 2- | sulfite | Na2SO3 |
| H2SO4 | sulfuric | SO 4 2- | sulfate | CaSO 4 (anhydrite) |
| HClO | hypochlorous | ClO- | hypochlorite | NaClO |
| HClO2 | chloride | ClO2 - | chlorite | NaClO2 |
| HClO3 | hypochlorous | ClO3 - | chlorate | NaClO3 |
| HClO4 | chlorine | ClO4 - | perchlorate | NaClO4 |
| H2CO3 | coal | CO 3 2- | carbonate | CaCO 3 (limestone, chalk, marble) |
| HNO3 | nitrogen | NO 3 - | nitrate | AgNO 3 (lapis) |
| HNO2 | nitrogenous | NO 2 - | nitrite | KNO 2 |
| H3PO4 | phosphorus | PO 4 3- | phosphate | AlPO 4 |
| H2SiO3 | silicon | SiO 3 2- | silicate | Na 2 SiO 3 (liquid glass) |
| HMnO4 | manganese | MnO4- | permanganate | KMnO 4 (potassium permanganate) |
| H2CrO4 | chrome | CrO 4 2- | chromate | CaCrO4 |
| H2S | hydrogen sulfide | S- | sulfide | HgS (cinnabar) |
Chemical properties
As a class, salts are characterized by their chemical properties by the fact that they can interact with alkalis, acids, salts and more active metals:
1. When interacting with alkalis in solution, a prerequisite for the reaction is the precipitation of one of the resulting substances.
2. When interacting with acids, the reaction takes place if a volatile acid, insoluble acid or insoluble salt is formed. Examples:
- Carbonic acid is a volatile acid, as it easily disintegrates into water and carbon dioxide: MgCO 3 + 2HCl = MgCl 2 + H 2 O + CO 2.
- Insoluble acid - silicic acid, is formed as a result of the reaction of silicate with another acid.
- One of the signs chemical reaction is precipitation. Which salts can be seen in the solubility table.
3. The interaction of salts with each other occurs only in the case of binding of ions, i.e. one of the formed salts precipitates.
4. To determine whether a reaction will occur between a metal and a salt, you need to refer to the metal voltage table (sometimes called the activity series).
Only more active metals (located to the left) can displace metal from the salt. An example is the reaction of an iron nail with copper sulfate:
CuSO 4 + Fe= Cu + FeSO 4
Such reactions are characteristic of most representatives of the salt class. But there are also more specific reactions in chemistry, the properties of the salt reflect individual properties, for example, decomposition during incandescence or the formation of crystalline hydrates. Each salt is individual and unusual in its own way.