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Hydroxides classification and chemical properties. Hydroxides




Hydroxides called complex substances containing the OH - group, which is connected through an oxygen atom by a single chemical bond with various chemical elements. Like oxides, depending on the nature of the E-OH chemical bond, hydroxides are divided into basic (grounds) (NaOH, Tl (OH), Cu (OH), Mg (OH) 2, Ba (OH) 2, Cr (OH) 2) with a predominantly ionic bond, amphoteric (I (OH), Be (OH) 2, B (OH) 3), Zn (OH) 2, Fe (OH) 3, Al (OH) 3) with an ion-covalent type of bond and acidic (oxygen-containing or oxoacids) (NO 2 (OH)ÛHNO 3 , PO(OH) 3 ÛH 3 PO 4 , SO 2 (OH) 2 ÛH 2 SO 4 , Te(OH) 6 ÛH 6 TeO 6), ClO 3 (OH)ÛHClO 4 , MnO 2 (OH) 2 ÛH 2 MnO 4 , MnO 3 (OH)ÛHMnO 4) with a predominantly covalent bond.

In accordance with the predominantly ionic nature of the chemical bond E-OH basic hydroxides (bases) when dissolved in water, they dissociate with the formation of hydroxide ions and cations, and, depending on the efficiency (degree) of dissociation, they distinguish strong bases(NaOH, Ba (OH) 2), dissociating almost completely, foundations of medium strength(Tl(OH), Mg(OH) 2, Cr(OH) 2) and weak bases(Сu (OH), Fe (OH) 2), the dissociation of which proceeds partially:

NaOH ® Na + + OH - , Fe(OH) 2 Û Fe 2+ + 2OH -

Acid hydroxides (oxoacids) in aqueous solutions, they dissociate to form hydronium ions H 3 O + , which are often abbreviated as the hydrogen cation H + . Like bases, acid hydroxides, according to the degree of their dissociation, are divided into strong(HNO 3 , HClO 4), medium strength(HAsO 3 , HClO 2) and weak(HClO, H 5 IO 6) acids:

HNO 3 + H 2 O ® H 3 O + + NO 3 - (HNO 3 ® H + + NO 3 -)

HClO + H 2 O H 3 O + + ClO - (HClO ® H + + ClO -)

Acids are arranged in descending order of their strength (activity) in the so-called acid activity series:

Strong Medium strength

HI>HBr>HClO 4>HCl>H 2 SO 4>HMnO 4>HNO 3 │>H 2 Cr 2 O 7>H 2 CrO 4>H 2 SO 3>H 3 PO 4>HF│

Weak

> HNO 2 > HCOOH > CH 3 COOH > H 2 CO 3 > H 2 S > HClO > HCN > H 3 BO 3 > H 2 SiO 3

Amphoteric hydroxides mostly poorly soluble in water and exhibit both weak basic and acidic properties:

OH - + I + Û I(OH), HIO Û IO - + H +

2OH - + Zn 2+ Û Zn(OH) 2 + 2H 2 O Û 2- + 2H +

The formation of hydroxonium cations, or hydroxide ions, during the dissociation of hydroxides determines the most important chemical property of hydroxides - the neutralization reaction, leading to the formation of water and salt during the interaction of bases and acids:

NaOH (Na + OH -) + HNO 3 (H + + NO 3 -) = NaNO 3 (Na + + NO 3 -) + H 2 O

OH - + H + \u003d H 2 O

Possessing acid-base duality, amphoteric hydroxides in neutralization reactions can act both as a base and as an acid:

I(OH) + HClO 4 = IClO 4 + H 2 O

HIO + NaOH = NaIO + H2O

Like amphoteric metal oxides, interaction with bases of their hydroxides in aqueous solutions leads to the formation of salts containing not oxo-, but hydroxo-complex anions:

Al(OH) 3 ¯ + 3NaOH \u003d Na 3

The formation of oxosalts occurs during the interaction of amphoteric hydroxides with alkaline melts:

Al (OH) 3 ¯ + NaOH (melt) \u003d NaAlO 2 + 2H 2 O

Depending on the number of OH - groups contained in the hydroxide, acid hydroxides are divided into one- (HNO 3), two- (H 2 SO 4), three- (H 3 PO 4), etc. basic acids, and basic hydroxides - into one- (NaOH), two- (Ca (OH) 2), three- (Al (OH) 3) acid bases.

By solubility bases are divided into soluble and insoluble. Bases of alkali (Li, Na, K, Rb, Cs) and alkaline earth (Ca, Sr, Ba) metals are soluble in water and are called alkalis.

Systematic names for basic and amphoteric hydroxides formed from the word hydroxide and the Russian name of the element in the genitive case, indicating (for elements with a variable oxidation state) in Roman numerals in parentheses the oxidation state of the element:

NaOH - sodium hydroxide, Ca (OH) 2 - calcium hydroxide,

TlOH - thallium (I) hydroxide, Fe (OH) 3 - iron (III) hydroxide.

The trivial names of some hydroxides, mainly used in the technical literature, are given in Appendix 2.

It should be noted the specificity of the name of an aqueous solution of ammonia, the partial dissociation of which leads to the formation of hydroxide ions in the solution and the manifestation of weak basic properties. Previously, it was believed that in an aqueous solution, ammonia forms ammonium hydroxide of the composition NH 4 OH. However, it has now been established that the main form of existence of ammonia in an aqueous solution is its hydrated molecules, which are conditionally written as NH 3 × H 2 O and called ammonia hydrate. Like ammonia, aqueous solutions of hydrazine N 2 H 4 and hydroxylamine NH 2 OH also mainly contain hydrated molecules, which are called: N 2 H 4 × H 2 O - hydrazine hydrate and NH 2 OH × H 2 O - hydroxylamine hydrate.

Exercises:

10. Give systematic names of hydroxides, classify them according to acidity and solubility: LiOH, Sr(OH) 2 , Cu(OH) 2 , Cd(OH) 2 , Al(OH) 3 , Cr(OH) 3 . Give the formulas of the corresponding oxides.

11. Give the molecular and graphical formulas of hydroxides: iron (III) hydroxide, beryllium hydroxide, lithium hydroxide, chromium (III) hydroxide, magnesium hydroxide. Which of these hydroxides will interact with a) potassium hydroxide, b) barium oxide, c) hydrochloric acid? Write reaction equations.

12. Give reactions that demonstrate the acid-base properties of barium, zinc, potassium and chromium (III) hydroxides, as well as methods for their preparation.

Systematic names acid hydroxides (oxoacids) are built according to the nomenclature rules for complex compounds, which will be discussed below. At the same time, in domestic practice are widely used traditional names common oxo acids - carbonic, sulfuric, phosphoric, etc. Their use is permissible, but only for a limited range of the really most common acids, and in other cases, systematic names should be used.

traditional name oxoacids consists of two words: the name of the acid expressed by the adjective and the group word acid. Name of the acid formed from Russian name of the acid-forming element(if the element name has the ending "й", "о", "а", then it is omitted) with the addition, depending on the oxidation state of the element, of various endings(Tables 1.3, 1.4). Traditionally, H 2 CO 3 is called coal, not carbonic acid.

In accordance with the Mendeleev rule of "parity" for acid-forming p-elements of groups IV-VI, the oxidation states corresponding to the group number N, as well as N-2 and N-4, are most characteristic.

As can be seen from Table. 1.2, for the highest oxidation state of the element N the name of the acid is formed by adding the endings to the name of most of the elements: -naya, -eva and –new . For arsenic and antimony, according to the rules of the Russian language, endings are used -yannaya and –yanaya. Name of acids with the oxidation state of the element N-2 is formed mainly is formed with the help of the ending – pure (for sulfur, arsenic and antimony: –nistaya, -ovist and - yistaya ). Acids formed by the elements with the lowest oxidation states N-4, have endings – novelty . For phosphorous H 2 PHO 3 and hypophosphorous HPH 2 O 2 acids, which are characterized by a specific structure due to the presence of P-H bonds, it is recommended to use special names - phosphonic and phosphine.

In some cases, the formation two forms of acids, in which the acid-forming element is in the same oxidation state. The prefix is ​​added to the name of the acid with more hydroxo groups ortho-, and the prefix is ​​added to the name of the acid with a smaller number of hydroxo groups meta-.

Table 3. Traditional names of oxoacids of group III-VI p-elements.

N E z+ The ending Name of the acid
III B3+ -naya H3BO3 ortho boron naya, HBO 2 meta boron naya,H 2 B 4 O 7 tetra boron naya
Al 3+ -eva H 3 AlO 3 ortho aluminum left, HАlO 2 metaaluminum left
IV C4+ -naya H 2 CO 3 coal
Si 4+ -eva H4SiO4 ortho flints left, H 2 SiO 3 meta flints left
Ge 4+ -eva H 4 GeO 4 ortho germany left, H 2 GeO 3 meta germany left
sn 4+ -yannaya H4SnO4 ortho olo spicy, H 2 SnO 3 meta tin yannaya
V N 5+ -naya HNO 3 nitrogen naya
P5+ -naya H3PO4 ortho phosphorus naya, HPO 3 meta phosphorus naya, H4P2O7 di phosphorus naya, H 5 P 3 O 10 three phosphorus naya
AS 5+ -ovaya H 3 AsO 4 ortho arsenic new, HasO 3 meta arsenic new
Sb 5+ -yanaya H3SbO4 ortho antimony, HSbO 3 meta antimony Yanaya
VI S 6+ -naya H 2 SO 4 ser naya, H 2 S 2 O 7 di ser naya
Se 6+ -ovaya H 2 SeO 4 selenium new
Te 6+ -ovaya H 6 TeO 6 ortho tellurium new, H 2 TeO 4 meta telluriumnew
V N 3+ -ista HNO 2 nitrogen true
P3+ -ista H 2 PHO 3 phosphorus true(phosphonic)
As 3+ - ovist H 3 AsO 3 ortho arsenic ovist, HasO2 meta arsenic ovist
Sb 3+ - yanistaya H3SbO3 ortho antimony sallow, HSbO2 meta antimony yistaya
VI S4+ -nistaya H 2 SO 3 ser nistaya
Se4+ -ista H 2 SeO 3 selenium true
Te 4+ -ista H 2 TeO 3 tellurium true
V N+ - novelty H 2 N 2 O 2 nitrogen novelty
P+ - novelty HPH 2 O 2 phosphorus novelty(phosphine)

Traditional names for halogen oxoacids (Table 4) in the highest oxidation state N, are also formed by adding the ending element to the name –naya . However, for halogen oxoacids in the oxidation state N-2 endings are used –new , and the ending – pure used to name acids with halogen oxidation state N-4. Halogen oxoacids with the lowest oxidation states N-6 have endings – novelty .

Despite the fact that the characteristic oxidation states of transition d-elements do not obey the Mendeleev rule of "parity", the highest oxidation state of d-metals forming side subgroups of III-VII groups is also determined by the group number N and traditional names for their oxoacids are formed like p-elements with the help of endings - ova, -eva : H 4 TiO 4 titanium new, H 3 VO 4 vanadium eva, H 2 CrO 4 chromium ova, H2Cr2O7 di chromium new, HMnO 4 manganese left. For oxoacids of d-elements in lower oxidation states of the metal, it is recommended to use systematic names formed according to the rules for complex compounds.

Table 4. Traditional names of oxoacids of group VII p-elements.

N E z+ The ending Name of the acid
The highest oxidation state of the element N
VII Cl7+ -naya HClO 4 chlorine naya
Br7+ HBrO 4 bromine naya
I 7+ H5IO6 ortho iodine naya, HIO 4 meta iodine naya
The oxidation state of the element N-2
VII Cl5+ -new HClO 3 chlorine new
Br5+ HBrO 3 bromine new
I 5+ HIO 3 iodine new
The oxidation state of the element N-4
VII Cl3+ -ista HClO 2 chlorine true
Br3+ HBrO 2 bromine true
I 3+ HIO 2 iodine true
The oxidation state of the element N-6
VII Cl + - ovate HClO chlorine novelty
Br+ HBrO bromine novelty
I+ HIO iodine novelty

Exercises:

13. Give the traditional names and graphic formulas of the following oxo acids: H 2 SO 4 , H 2 S 2 O 7 , HNO 3 , HNO 2 , H 3 PO 4 , HPO 3 , H 4 P 2 O 7 , H 2 PHO 3 , HPH 2 O 2 , HClO, HClO 2 , HClO 3 , HClO 4 , H 5 IO 6 , HMnO 4 , H 2 Cr 2 O 7 .

14. Give the molecular and graphic formulas of the following oxo acids: hypobromous, iodic, selenous, orthotelluric, metaarsenic, disilicic, metatin, phosphorous (phosphonic), hypophosphorous (phosphine), pentaphosphoric, metavanadium.

15. Give reactions that demonstrate the general methods for obtaining oxo acids. Give examples of oxides of elements in intermediate oxidation states, which, when interacting with water, form two acids.

16. Write the dehydration reactions of the following acids: H 3 BO 3 , HMnO 4 , H 2 S 2 O 7 , HNO 2 , H 3 PO 4 , H 2 WO 4 , H 3 AsO 3 , H 2 CrO 4 . Give the names of acids and the resulting acid oxides (acid anhydrides).

17. Which of the following substances will interact with hydrochloric acid: Zn, CO, Mg (OH) 2, CaCO 3, Cu, N 2 O 5, Al (OH) 3, Na 2 SiO 3, BaO? Write reaction equations.

18. Write reactions that demonstrate the acidic nature of the following oxides, name the acids corresponding to them: P 4 O 10, SeO 3, N 2 O 3, NO 2, SO 2, As 2 O 5.

19. Give the reactions of mutual transition between phosphoric acids: H 3 PO 4 ®HPO 3 , H 3 PO 4 ®H 4 P 2 O 7 , HPO 3 ®H 3 PO 4 , HPO 3 ®H 4 P 2 O 7 , H 4 P 2 O 7 ®HPO 3 , H 4 P 2 O 7 ®H 3 PO 4 .

Peroxoacids.

Acid hydroxides containing a peroxide group -О-О- received a group name peroxoacids . The peroxide group in the composition of peroxo acids can replace both the oxygen atom in the hydroxide group and the bridging oxygen atom that unites the atoms of the acid-forming element in polynuclear acid hydroxides:

When writing peroxoacid formulas, it is recommended to enclose the peroxide group in parentheses and write it on the right side of the formula. The traditional names for peroxoacids are formed from the name of the corresponding oxoacid with the addition of the prefix peroxo- . If there are several peroxide groups in the peroxoacid, their number is indicated by a numerical prefix: di-, tri-, tetra- etc. For example: HNO 2 (O 2) peroxonitric acid, H 3 PO 2 (O 2) 2 diperoxophosphoric acid.

An exercise:

9. Give the traditional names and graphic formulas of the following peroxo acids: H 3 PO 2 (O 2), H 4 P 2 O 6 (O 2), H 3 BO 2 (O 2).

9.4. Thio acids, polythionic and other substituted oxo acids * -section for in-depth study.

Oxo acids in which some or all of the oxygen atoms are replaced by sulfur atoms are called thio acids . When writing the formulas of thioacids, it is recommended to place sulfur in the last place on the right - H 3 PO 3 S, H 3 PO 2 S 2, H 3 POS 4, H 3 PS 4:

Traditional names for thioacids formed from the name of the corresponding oxoacid with the addition of the prefix thio- ; when two or more oxygen atoms are replaced by sulfur atoms, their number is indicated by numerical prefixes: di-, tri-, tetra- etc.

Oxo acids of the general formula H 2 (O 3 S-S n -SO 3) (n = 0¸4) are called polition. A characteristic feature of their structure (with the exception of H 2 S 2 O 6) is the presence of bridging sulfur atoms that combine two structural (SO 3 )-groups:

In dithionic acid, two structural groups are united directly by sulfur atoms, acid-forming H 2 (O 3 S-SO 3). The traditional names of polythionic acids consist of a hmsword prefix indicating the total number of sulfur atoms in the composition and a group ending -thionic acid.

Acid hydroxides, in which part of the hydroxide groups or oxygen atoms are replaced by other halogen atoms or -NH 2, \u003d NH groups, are called substituted acids. The traditional names of such acids are formed from the name of the corresponding oxo acid with the addition of a prefix composed of the name of the substituting halogen atoms or groups (NH 2 - amide , NH- imide ) and a connecting vowel -about. In the formulas of such acids, substituent atoms or groups are placed last.

Traditionally, substituted sulfuric acids are called sulfonic acids:

HSO 3 F - fluorosulfonic, HSO 3 Cl - chlorosulfonic,

HSO 3 (NH 2) - amidosulfonic acid, H 2 S 2 O 4 (NH) - imidodisulfonic acid.

Exercises:

10. Give the traditional names of substituted oxo acids: HSeO 3 F, HAsO 2 Cl 2 , H 2 CS 3 , H 3 POS 3 , H 2 AsO 3 (NH 2).

11. Give the molecular and graphical formulas of acids: thiosulfuric, trithionic, dithioantimony, amidosulfonic, dibromoarsenic, amidocarbonic.

Anoxic acids.

Aqueous solutions of hydrogen compounds of chalcogens (H 2 S, H 2 Se, H 2 Te) and halogens (HF, HCl, HBr, HI), as well as pseudohalogens(HCN, HNCS, HCNO, HN 3), in which the role of electronegative components (anions) is played by groups of atoms with halide-like properties, exhibit acidic properties and dissociate with the formation of hydroxonium ions. They form a family anoxic acids.

Systematic name of anoxic acids formed from Russian name of an element or a special name of a pseudohalide group with the addition of a connecting vowel -about and phrases hydrochloric acid:

HF - fluorine hydride acid, H 2 Te - tellurium hydride acid,

HCN - cyan hydride acid, HNCS - thiocyanate hydride acid,

HN 3 - azide hydride acid (or nitrous hydride acid).

Historically, for aqueous solutions of a number of anoxic acids in chemical practice, they also use trivial names(see appendix 2):

HF - hydrofluoric acid, HCl - hydrochloric acid,

HCN - hydrocyanic acid, H 2 S - hydrogen sulfide water.

An exercise:

12. Give systematic and trivial names of oxygen-free acids: HCl, HCN, HBr, HNCS, HI, H 2 S, HF, H 2 Se.

13. Give the formulas of the following acids: hydrocyanic, hydrobromic, hydrofluoric, hydroazide, hydrosulfide, thiocyanic, hydroiodic, cyanic, thiocyanate.

Acid halides.

Acid halides call complex substances that can be considered as products of the complete replacement of hydroxide groups in the molecules of oxo acids by halogen atoms. Thus, acid halides are the final member of a series of successive transformations of oxoacids when hydroxide groups are replaced by halogen atoms: oxoacid ® halogenated oxoacid ® acid halide. For example, POCl 3 is the end member of a series of successive substitutions of three hydroxide groups in phosphoric acid:

Some acid halides can be considered as derivatives of unstable oxo acids - for example, CCl 4 and PCl 5 are formally acid chlorides of fully hydrated acid hydroxides of carbon (IV) H 4 CO 4 and phosphorus (V) H 5 PO 5 , in which the number of hydroxide groups coincides with the degree oxidation of the acid-forming element. Acid halides can contain either atoms of only one halogen, or atoms of different halogens: POCl 3 , POBrCl 2 , POIBrCl.

In chemical practice, for acid halides, several methods are used to construct their names. :

According to the rules systematic nomenclature for complex connections using latin number prefixes indicating the number of electronegative halide and oxide halide ions:

PCl 3 - phosphorus trichloride, PCl 5 - phosphorus pentachloride,

POCl 3 - trichloride-phosphorus oxide, POBrCl 2 - dichloride-bromide-phosphorus oxide;

According to the rules systematic nomenclature for binary compounds indicating according to the Stock method Roman numerals in parentheses indicate the oxidation state of the element:

PCl 3 - phosphorus (III) chloride, PCl 5 - phosphorus (V) chloride;

- traditional names form with the help of numerical prefixes indicating the number of halogen atoms, the Russian name for halogens, endings – anhydride and the names of the acid in the genitive case: PCl 3 - phosphorous acid trichloride, POCl 3 - phosphoric acid trichloride, POBrCl 2 - phosphoric acid dichlorobromoanhydride;

For sulfuric and sulphurous acid halides, limited use is allowed special titles, in which special names of cations are used: SO 2 2+ - sulfuril and SO2+ - thionyl:

SO 2 Cl 2 - sulfuryl chloride, SO 2 FCl - sulfuryl chloride fluoride,

SOBr 2 - thionyl bromide, SOF 2 - thionyl fluoride.

A characteristic chemical property of acid halides is their effective interaction with water to form hydrohalic and oxo acids:

PCl 5 + 3H 2 O \u003d H 3 PO 4 + 5HCl

POBrCl 2 + 3H 2 O \u003d H 3 PO 4 + 2HCl + HBr

Exercises:

14. Give the systematic and traditional names of acid halides and write the reactions of their interaction with water: SbOCl, SeO 2 F 2 , NOBr, NO 2 F 2 , NF 3 , AsOCl 2 F, CO 2 Cl 2 , SOCl 2 , SO 2 Br 2 .

15. Give the molecular and graphical formulas of acid halides: boron chloride-oxide, silicon(IV) bromide, silicon difluoride-oxide, sulfuryl fluoride, selenous acid dichloride, sulfuryl bromide, thionyl chloride, orthophosphoric acid chlorobromoiodoanhydride, orthoarsenic acid dichlorobromoanhydride, thionyl fluoride.

Salt.

salt are one of the most capacious classes of inorganic compounds in terms of the number of chemical compounds. They are formed as a result of a wide variety of chemical processes and, in particular, are the products of acid-base reactions of the interaction of basic and acid binary E n X m and polyelement chemical compounds, characterized, respectively, by the predominantly ionic and covalent character of the E-X chemical bond (Table 1.5) .

Table 1.5. Acid-base reactions of salt formation.

Connections Salt reaction
Main Acidic
NaF PF 5 NaF + PF 5 = Na
Na2O P2O5 3Na 2 O + P 2 O 5 \u003d 2Na 3 Na 2 O + P 2 O 5 \u003d 2Na
Na 2 S P 2 S 5 3Na 2 S + P 2 S 5 \u003d 2Na 3 Na 2 S + P 2 S 5 \u003d 2Na
Na 3 N P 3 N 5 Na 3 N + P 3 N 5 \u003d Na 4
NaH AlH 3 NaH + AlH 3 = Na
NaOH Al(OH)3 NaOH + Al(OH) 3 = Na NaOH + Al(OH) 3 = Na + H 2 O
NaNO 3 I(NO3) NaNO 3 + I (NO 3) \u003d Na
NaOH HNO3 NaOH + HNO 3 \u003d Na + H 2 O
Al(OH)3 H3PO4 Al (OH) 3 + H 3 PO 4 \u003d Al + 6H 2 O 2Al (OH) 3 + 3H 3 PO 4 \u003d Al 2 3 + 6H 2 O Al (OH) 3 + 3H 3 PO 4 \u003d Al 3 + 3H 2 O 3Al(OH) 3 + 2H 3 PO 4 = (AlOH) 3 2 + 6H 2 O 3Al(OH) 3 + H 3 PO 4 = (Al(OH) 2 ) 3 + 3H 2 O
NaOH + Ba(OH) 2 H3PO4 NaOH + Ba(OH) 2 + H 3 PO 4 = (NaBa) + 3H 2 O
Al(OH)3 H2SO4 + HNO3 Al(OH) 3 + H 2 SO 4 + HNO 3 = Al[(SO 4)NO 3] + H 2 O

In the composition of salts, cationic and anionic components can be distinguished, which are derivatives of the original basic and acidic compounds and have a predominantly ionic nature of the chemical bond. As a result, in melts and solutions, salts undergo the process of electrolytic dissociation, leading to the formation of cations and anions.

Depending on the composition, salts are classified according to the nature of cations and anions:

salt with complex cations based on two different metal ions or an ammonium ion and a metal (((KAl) 2, ((NH 4) 2 Fe) 2) are called double salts, and salts with complex anions(Ca[(ClO)Cl], Fe[(SO 4)NO 3]) – mixed salts:


- salts whose cations include hydroxide groups(Al (OH), (Al (OH)) 2, Al (OH) 2 Cl) and capable of exhibiting basic properties due to the formation of OH - ions as a result of the process of electrolytic dissociation of the cation - for example:

Al(OH)SO 4 ®Al(OH) 2+ + SO 4 2-

Al(OH) 2+ Û Al 3+ + OH -

called main . Such salts can be considered as products of partial replacement of hydroxide groups in basic hydroxides by groups that are acidic residues of the corresponding oxo- or anoxic acids:

- salts whose anions contain hydrogen atoms((NH 4), NaHS) and are able to exhibit acidic properties due to the formation of hydronium ions during the electrolytic dissociation of the anion - for example:

NaHS® Na + + HS - , HS - Û H + + S 2-

called sour . Such salts can be considered as products of partial replacement of hydrogen in acids by metal or ammonium cations:


- salts that are products of the complete replacement of hydroxide groups with acidic residues or hydrogen atoms with metal (ammonium) cations are called average or normal .

Some salts, when crystallized from aqueous solutions, form crystal lattices containing water molecules - for example: CuSO 4 × 5H 2 O, Na 2 SO 4 × 10H 2 O. Such salts are called crystalline hydrates .

As can be seen from Table. 1.5, acidic and basic salts are formed as a result of neutralization reactions at various ratios of polybasic acids and polyacid bases and easily pass both into each other and into medium salts: Al (H 2 PO 4) 3 + Al (OH) 3 \u003d Al 2 (HPO 4) 3 + 3H 2 O

Al 2 (HPO 4) 3 + Al (OH) 3 \u003d 3AlPO 4 + 3H 2 O

2AlPO 4 + Al(OH) 3 = (AlOH) 3 (PO 4) 2

(AlOH) 3 (PO 4) 2 + 3Al (OH) 3 \u003d 2 (Al (OH) 2) 3 PO 4

(Al(OH) 2 ) 3 PO 4 + H 3 PO 4 = (AlOH) 3 (PO 4) 2 + 3H 2 O

(AlOH) 3 (PO 4) 2 + H 3 PO 4 = 3AlPO 4 + 3H 2 O

2AlPO 4 + H 3 PO 4 \u003d Al 2 (HPO 4) 3

Al 2 (HPO 4) 3 + H 3 PO 4 \u003d 2Al (H 2 PO 4) 3

Systematic names of medium salts of oxygen-free salts form according to the general rules for binary compounds:

Na 2 S - sulf id sodium, FeCl 3 - chlorine id iron(III) (iron trichloride),

Cu(CN) 2 - cyan id copper (II), AgCNS - silver thiocyanate.

Systematic names of salts of oxo acids and their derivatives are formed according to the rules of nomenclature for complex compounds, which will be discussed below. At the same time, as for acids, traditional names are widely used in chemical practice for the most common salts of oxoacids.

Traditional names for salts consist of the names of anions and cations. The name of anions of medium salts of common oxo acids is built from the roots of Russian or Latin (Table 1.) names of acid-forming elements with appropriate endings and prefixes depending on their degree of oxidation (Table 6, 7) and through a hyphen with a group word -and he. For p-elements of III-VI groups in the highest oxidation state, the ending is used in the name of the anions -at , to a lower degree (N-2) - suffix –it and for N + and P + - to the stack hypo- and ending –it .

For halogens in the +7 oxidation state, the prefix is ​​used in the name of the anions per- and ending -at ; for oxidation states: +5 - ending -at , +3 - ending –it and for the lowest +1 - the prefix hypo- and ending –it .

Various attachments: meta-, ortho-, di-, tri- etc., used in the name of oxo acids to indicate their form, are also preserved in the names of anions.

For oxoanions formed by d-elements, systematic names are mainly used, and only for a limited range of anions (Table I-5.) Traditional names are used in chemical practice.

Generally, traditional name for intermediate salts of oxoacids is built from the name of the anion (group word -and he is omitted) and the Russian name of the cation in the genitive case, indicating its oxidation state in Roman numerals in parentheses (if it can be variable):

Fe 2 (S 2 O 7) - iron (III) disulfate, Na 3 PO 4 - sodium orthophosphate,

Ba 5 (IO 6) - barium orthoperiodate, NiSeO 3 - nickel (II) selenite,

NaPH 2 O 2 - sodium hypophosphite, KMnO 4 - potassium permanganate.

Table 6. Traditional names of oxoanions of p-elements of III-VI groups.

Physical properties

The general formula of alkali metal hydroxides is MON.

All alkali metal hydroxides are colorless hygroscopic substances, easily deliquescent in air, very well soluble in water and ethanol, with the transition from LiOH to CsOH, the solubility increases.

Some physical properties of alkali metal hydroxides are given in the table.

Chemical properties

Hydroxides of all alkali metals melt without decomposition, lithium hydroxide decomposes when heated to a temperature of 600 ° C:

2LiOH \u003d Li 2 O + H 2 O.

All hydroxides exhibit the properties of strong bases. In water, they dissociate almost completely:

NaOH \u003d Na + + OH -.

React with oxides of non-metals:

KOH + CO 2 \u003d KHCO 3;

2NaOH + CO 2 \u003d Na 2 CO 3 + H 2 O;

2KOH + 2NO 2 = KNO 3 + KNO 2 + H 2 O.

Interact with acids, enter into a neutralization reaction:

NaOH + HCl \u003d NaCl + H 2 O;

KOH + HNO 3 \u003d KNO 3 + H 2 O.

Enter into exchange reactions with salts:

2NaOH + CuCl 2 = Cu(OH) 2 + 2NaCl.

React with halogens:

2KOH + Cl 2 \u003d KClO + KCl + H 2 O (in the cold);

6KOH + 3Cl 2 \u003d KClO 3 + 5KCl + 3H 2 O (when heated).

In the molten state, they interact with amphoteric metals and their oxides:

2KOH + Zn \u003d K 2 ZnO 2 + H 2;

2KOH + ZnO = K 2 ZnO 2 + H 2 O.

Aqueous solutions of hydroxides, when interacting with amphoteric metals, their oxides and hydroxides, form hydroxo complexes:

2NaOH + Be + 2H 2 O \u003d Na 2 + H 2;

2NaOH + BeO + H 2 O \u003d Na 2;

2NaOH + Be(OH) 2 = Na 2 .

Aqueous solutions and melts of hydroxides react with boron and silicon, their oxides and acids:

4NaOH + 4B + 3O 2 = 4NaBO 2 + 2H 2 O (melt);

2NaOH + Si + H 2 O = Na 2 SiO 3 + 2H 2 (solution).

Receipt

Lithium, sodium and potassium hydroxides are obtained by electrolysis of concentrated solutions of their chlorides, while hydrogen is released at the cathode, chlorine is formed at the anode:

2NaCl + 2H 2 O H 2 + 2NaOH + Cl 2.

Rubidium and cesium hydroxides are obtained from their salts using exchange reactions:

Rb 2 SO 4 + Ba (OH) 2 \u003d 2RbOH + BaSO 4.

ALKALINE EARTH METALS

Properties of alkaline earth metals

atomic number Name Atomic mass Electronic configuration r g/cm 3 t°pl. °C t°boiling °C EO Atomic radius, nm Oxidation state
Beryllium Be 9,01 2s 2 1,86 1,5 0,113 +2
Magnesium Mg 24,3 3s 2 1,74 649,5 1,2 0,16 +2
Calcium Ca 40,08 4s 2 1,54 1,0 0,2 +2
Strontium Sr 87,62 5s 2 2,67 1,0 0,213 +2
Barium Ba 137,34 6s 2 3,61 0,9 0,25 +2
Radium Ra 7s 2 ~6 ~700 0,9 – +2

Physical properties

Alkaline earth metals (compared to alkali metals) have higher t°pl. and t ° boiling., ionization potentials, densities and hardness.

Chemical properties

1. Very reactive.

2. Have a positive valence of +2.

3. React with water at room temperature (except for Be) with evolution of hydrogen.

4. They have a high affinity for oxygen (reducing agents).

5. They form salt-like hydrides EH 2 with hydrogen.

6. Oxides have the general formula EO. The tendency towards the formation of peroxides is less pronounced than for alkali metals.

Being in nature

3BeO Al 2 O 3 6SiO 2 - beryl

MgCO 3 - magnesite

CaCO 3 MgCO 3 - dolomite

KCl MgSO 4 3H 2 O - kainite

KCl MgCl 2 6H 2 O - carnallite

CaCO 3 - calcite (limestone, marble, etc.)

Ca 3 (PO 4) 2 - apatite, phosphorite

CaSO 4 2H 2 O - gypsum

CaSO 4 - anhydrite

CaF 2 - fluorspar (fluorite)

SrSO 4 - celestine

SrCO 3 - strontianite

BaSO 4 - barite

BaCO 3 - witherite

Receipt

Beryllium is obtained by reduction of fluoride:

BeF 2 + Mg - t ° ® Be + MgF 2

Barium is obtained by oxide reduction:

3BaO + 2Al - t ° ® 3Ba + Al 2 O 3

The remaining metals are obtained by electrolysis of chloride melts:

CaCl 2 ® Ca + Cl 2

cathode: Ca 2+ + 2ē ® Ca 0

anode: 2Cl - – 2ē ® Cl 0 2

Metals of the main subgroup of group II are strong reducing agents; in compounds, they exhibit only the +2 oxidation state. The activity of metals and their reducing ability increases in the series: ––Be–Mg–Ca–Sr–Ba®

1. Reaction with water.

Under normal conditions, the surface of Be and Mg is covered with an inert oxide film, so they are resistant to water. In contrast, Ca, Sr and Ba dissolve in water to form hydroxides, which are strong bases:

Mg + 2H 2 O - t ° ® Mg (OH) 2 + H 2

Ca + 2H 2 O ® Ca (OH) 2 + H 2

2. Reaction with oxygen.

All metals form oxides RO, barium peroxide - BaO 2:

2Mg + O 2 ® 2MgO

Ba + O 2 ® BaO 2

3. Binary compounds are formed with other non-metals:

Be + Cl 2 ® BeCl 2 (halides)

Ba + S ® BaS(sulfides)

3Mg + N 2 ® Mg 3 N 2 (nitrides)

Ca + H 2 ® CaH 2 (hydrides)

Ca + 2C ® CaC 2 (carbides)

3Ba + 2P ® Ba 3 P 2 (phosphides)

Beryllium and magnesium react relatively slowly with non-metals.

4. All metals dissolve in acids:

Ca + 2HCl ® CaCl 2 + H 2

Mg + H 2 SO 4 (razb.) ® MgSO 4 + H 2

Beryllium also dissolves in aqueous solutions of alkalis:

Be + 2NaOH + 2H 2 O ® Na 2 + H 2

5. Qualitative reaction to alkaline earth metal cations - coloring of the flame in the following colors:

Ca 2+ - dark orange

Sr 2+ - dark red

Ba 2+ - light green

The Ba 2+ cation is usually opened by an exchange reaction with sulfuric acid or its salts:

Barium sulfate is a white precipitate, insoluble in mineral acids.

Alkaline earth metal oxides

Receipt

1) Oxidation of metals (except Ba, which forms a peroxide)

2) Thermal decomposition of nitrates or carbonates

CaCO 3 - t ° ® CaO + CO 2

2Mg(NO 3) 2 - t ° ® 2MgO + 4NO 2 + O 2

Chemical properties

Typical basic oxides. React with water (except BeO), acid oxides and acids

MgO + H 2 O ® Mg (OH) 2

3CaO + P 2 O 5 ® Ca 3 (PO 4) 2

BeO + 2HNO 3 ® Be(NO 3) 2 + H 2 O

BeO - amphoteric oxide, soluble in alkalis:

BeO + 2NaOH + H 2 O ® Na 2

Alkaline earth metal hydroxides R(OH) 2

Receipt

Reactions of alkaline earth metals or their oxides with water:

Ba + 2H 2 O ® Ba (OH) 2 + H 2

CaO (quicklime) + H 2 O ® Ca (OH) 2 (slaked lime)

Chemical properties

Hydroxides R (OH) 2 - white crystalline substances, soluble in water worse than alkali metal hydroxides (the solubility of hydroxides decreases with decreasing serial number; Be (OH) 2 - insoluble in water, soluble in alkalis). The basicity of R(OH) 2 increases with increasing atomic number:

Be (OH) 2 - amphoteric hydroxide

Mg(OH) 2 - weak base

the remaining hydroxides are strong bases (alkalis).

1) Reactions with acid oxides:

Ca(OH) 2 + SO 2 ® CaSO 3 ¯ + H 2 O

Ba(OH) 2 + CO 2 ® BaCO 3 ¯ + H 2 O

2) Reactions with acids:

Mg (OH) 2 + 2CH 3 COOH ® (CH 3 COO) 2 Mg + 2H 2 O

Ba(OH) 2 + 2HNO 3 ® Ba(NO 3) 2 + 2H 2 O

3) Exchange reactions with salts:

Ba(OH) 2 + K 2 SO 4 ® BaSO 4 ¯+ 2KOH

4) The reaction of beryllium hydroxide with alkalis:

Be(OH) 2 + 2NaOH ® Na 2

Hardness of water

Natural water containing Ca 2+ and Mg 2+ ions is called hard. Hard water, when boiled, forms a scale, food products are not boiled in it; detergents do not produce foam.

Carbonate (temporary) hardness is due to the presence of calcium and magnesium bicarbonates in water, non-carbonate (permanent) hardness - chlorides and sulfates.

The total hardness of water is considered as the sum of carbonate and non-carbonate.

Water hardness is removed by precipitation of Ca 2+ and Mg 2+ ions from the solution.

Hydrates of oxides are collectively called hydroxides. . Bases (basic hydroxides) are called hydrates of basic oxides. The general formula is Me( Oh) n. The number of hydroxyl groups (OH) in a molecule determines its acidity.

Most bases are insoluble in water, only Hydroxides alkaline and alkaline earthmetals (they are called alkalis), as well as ammonium . In aqueous solutions, bases dissociate into a metal cation hydroxyl group, amphoteric hydroxides dissociateboth as an acid and as a base . Polyacid bases dissociate in steps:

Me x + +xOH - ⇌ Me(OH) x ≡H x MeO x ⇌ x H + +MeO x x - (dissociation of amphoteric hydroxide (general scheme))

*It is interesting

Now there are 3 main theories of acids and bases:

1. Brønsted-Lowry protolithic theory .In it acid-a molecule or ion capable of being a donor in a given reaction protons , respectively, the bases are molecules or ions that attach protons. Both acids and bases are called protoliths.

2. Lewis acid and base theory . In it, an acid is any particle capable of accepting a pair of electrons, and a base is a particle capable of donating this pair. The Lewis theory is very similar to the theory Bronsted - Lowry, but differs from it in that it covers a wider range of compounds.

3. Usanovich's theory. In it, an acid is a particle that can split off cations, including a proton, or add anions, including an electron. A base is a particle that can accept a proton and other cations or donate an electron and other anions. .

Nomenclature:

Inorganic compounds containing -OH groups are called hydroxides. NaOH - sodium hydroxide, Fe(OH) 2 - iron(II) hydroxide, Ba(OH )2-barium hydroxide. (in brackets the valency of the element is indicated (if it is a variable))

For compounds containing oxygen, the names of hydroxides are used, with the prefix "meta": AlO (OH) - aluminum metahydroxide, Mn O(OH) - manganese metahydroxide

For oxides hydrated with an indefinite number of water molecules, Me 2 O n n H 2 O, it is illegal to write formulas like Me(OH)n . Calling such compounds hydroxides is also not recommended. Name examples: Tl 2 O 3 ∙n H 2 O - thallium(III) oxide polyhydrate, MnO 2∙nH2 O - manganese(IV) oxide polyhydrate

There are also hydrates -NH 3 ∙H 2 O (hydrate ammonia) \u003d NH 4 OH (ammonium hydroxide).

Bases give salts when interacting with acids (neutralization reaction), when interacting with acid oxide, amphoteric hydroxide, amphoteric metal, amphoteric oxide, non-metal.

NaOH+HCl→NaCl+H 2 O(neutralization reaction)

2NaOH+2NO 2 →NaNO 3 +NaNO 2 +H 2 O(reaction with mixed anhydride)

Cl 2 +2KOH→KCl+KClO+H 2 O(reaction proceeds without heating)

Cl 2 +6KOH→5KCl+KClO 3 +3H 2 O(reaction proceeds with heating)

3S+6NaOH→2Na 2 S+Na 2 SO 3 +3H 2 O

2Al+2NaOH+6H 2 O→2Na+3H 2

Al 2 O 3 + 6NaOH → 2Na 3 AlO 3 +3H 2 O

NaOH+Al(OH) 3 →Na

Methods for obtaining bases:

1. Interaction of alkali and alkaline earth metals, and ammonia with water. Metals (only alkali or alkaline earth), interacting with water form alkali and release hydrogen. Ammonia interacting with water forms an unstable compound NH 4OH:

2Na+2H 2 O→2NaOH+H 2

Ba+2H 2 O→ Ba ( Oh ) 2 +H 2

NH 3 +H 2 O↔NH 4 Oh

2. Direct attachment by basic oxides to water. Most basic oxides do not directly add water, only oxides of alkali metals (alkali metals) and alkaline earth metals (alkaline earth metals), attaching water, form bases:

Li 2 O+H 2 O→2LiOH

BaO+H 2 O→ Ba ( Oh ) 2

3. Salt interaction . This is one of the most common ways to obtain salts and bases. Since this is an ion exchange reaction, both reactants must be soluble, and one of the products must not:

NaOH+FeCl 3 →3NaCl+Fe(OH) 3 ↓

Na 3 PO 4 +3LiOH→3NaOH+Li 3 PO 4 ↓

4. Electrolysis of salt solutionsalkaline and alkaline earth metals .In the electrolysis of solutionssalt data metals neverare not released at the cathode (instead, hydrogen is released from water: and 2H 2 O-2e - \u003d H 2 ↓ + 2OH - ), and the halogen is reduced at the anode (all except F - ), or in the case of an oxygen-containing acid, the following reaction occurs:

2H 2 O-4e - =4H + +O 2 , halogens are reduced according to the scheme: 2X - -2e - =X 2 (where X is halogen)

2NaCl+2H 2 O→2NaOH+Cl 2 +H 2

An alkali accumulates in an aqueous solution, which can then be isolated by evaporating the solution.

It is interesting:

Peroxides and superoxides of alkali and alkaline earth metals react with water to form the corresponding hydroxide and hydrogen peroxide.

Na 2 O 2 +2 H 2 O →2 NaOH + H 2 O 2

4NaO 2 + 2 H 2 O →4 Na Oh + 3O 2

The Bronsted-Lowry theory makes it possible to quantify the strength of bases, that is, their ability to split off a proton from acids. This is usually done using the basicity constant K b . For example, for ammonia as a Bronsted base, one can write:

NH 3 + H 2 O ↔ NH 4 + +OH -

For a more convenient display of the basicity constants, a negative logarithm is used: pK b = -log K b . It is also logical that the strength of the bases increases in the series of metal stresses from right to left.

NaOH + C 2 H 5 Cl → NaCl + C 2 H 4 + H 2 O (a method for obtaining alkenes, ethylene (ethene) in this case), an alcohol solution of sodium hydroxide was used.

NaOH + C 2 H 5 Cl → NaCl + C 2 H 5 Oh (a method for obtaining alcohols, ethanol in this case), an aqueous solution of sodium hydroxide was used.

2 NaOH + C 2 H 5 Cl →2 NaCl + C 2 H 2 + H 2 O (a method for obtaining alkynes, acetylene (ethyne) in this case), an alcohol solution of sodium hydroxide was used.

C 6 H 5 Oh (phenol)+ NaOH → C 6 H 5 ONa + H 2 O

The product of substitution of one of the ammonia hydrogens for a hydroxyl group is hydroxylamine ( NH 2 Oh). It is formed during the electrolysis of nitric acid (with mercury or lead cathodes), as a result of its reduction by atomic hydrogen, which is formed as water is electrolyzed in parallel:

HNO 3 +6 H → NH 2 Oh +2 H 2 O

2 H 2 O → 2 H 2 + O 2

amphoteric hydroxides.

These compounds give salts both when interacting with acids (medium salts) and when interacting with bases (complex compounds). All amphoteric hydroxides are slightly soluble. Their dissociation can be considered both in terms of the basic and acidic types, but since these 2 processes occur simultaneously, the process can be written as follows (Me-metal):

Me x+ +xOH - ⇌ Me(OH) x ≡H x MeO x ⇌ xH + +MeO x x-

Since amphoteric hydroxides are hydrates of amphoteric oxides, their most prominent representatives are hydrates of the following oxides: ZnO, Al 2 O 3, BeO, SnO, PbO, Fe 2 O 3, Cr 2 O 3, MnO 2, TiO 2.

Reaction examples:

NaOH+Al(OH) 3 ↓→Na- sodium hydroxoalluminate

Al(OH) 3 ↓+3HCl→AlCl 3 +3H 2 O

But, knowing that amphoteric hydroxides also dissociate according to the acid type, one can write their interaction with alkalis using another equation:

Zn(OH) 2 ↓+2NaOH→Na 2 (in solution)

H 2 ZnO 2 ↓+2NaOH→Na 2 ZnO 2 +H 2 O(in melt)

1)H 3 AlO 3 ↓+3NaOH→Na 3 AlO 3 +3H 2 O(sodium orthoaluminate was formed here (the reaction took place in solution), but if the reaction occurs during fusion, sodium metaaluminate will be formed)

2) HAlO 2 +NaOH→NaAlO 2 +H 2 O(sodium metaaluminate was formed, which means that orthoaluminum and metaluminic acids entered into reactions 1 and 2, respectively)

Amphoteric hydroxides are usually obtained by the interaction of their salts with alkalis, the amount of which is accurately calculated according to the reaction equation:

3NaOH+ Cr(NO 3 ) 3 →3NaNO 3 +Cr(OH) 3 ↓

2NaOH+ Pb(CH 3 COO) 2 →2CH 3 COONa+Pb(OH) 2 ↓

Editor: Kharlamova Galina Nikolaevna

Bases (hydroxides)- complex substances, the molecules of which have one or more OH hydroxyl groups in their composition. Most often, bases consist of a metal atom and an OH group. For example, NaOH is sodium hydroxide, Ca (OH) 2 is calcium hydroxide, etc.

There is a base - ammonium hydroxide, in which the hydroxy group is attached not to the metal, but to the NH 4 + ion (ammonium cation). Ammonium hydroxide is formed by dissolving ammonia in water (reactions of addition of water to ammonia):

NH 3 + H 2 O = NH 4 OH (ammonium hydroxide).

The valence of the hydroxyl group is 1. The number of hydroxyl groups in the base molecule depends on the valency of the metal and is equal to it. For example, NaOH, LiOH, Al (OH) 3, Ca (OH) 2, Fe (OH) 3, etc.

All grounds - solids that have different colors. Some bases are highly soluble in water (NaOH, KOH, etc.). However, most of them do not dissolve in water.

Water-soluble bases are called alkalis. Alkali solutions are "soapy", slippery to the touch and quite caustic. Alkalis include hydroxides of alkali and alkaline earth metals (KOH, LiOH, RbOH, NaOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2, etc.). The rest are insoluble.

Insoluble bases- these are amphoteric hydroxides, which, when interacting with acids, act as bases, and behave like acids with alkali.

Different bases differ in their ability to split off hydroxy groups, so they are divided into strong and weak bases according to the feature.

Strong bases easily donate their hydroxyl groups in aqueous solutions, but weak bases do not.

Chemical properties of bases

The chemical properties of bases are characterized by their relationship to acids, acid anhydrides and salts.

1. Act on indicators. Indicators change their color depending on the interaction with different chemicals. In neutral solutions - they have one color, in acid solutions - another. When interacting with bases, they change their color: the methyl orange indicator turns yellow, the litmus indicator turns blue, and phenolphthalein turns fuchsia.

2. React with acidic oxides formation of salt and water:

2NaOH + SiO 2 → Na 2 SiO 3 + H 2 O.

3. React with acids, forming salt and water. The reaction of the interaction of a base with an acid is called a neutralization reaction, since after its completion the medium becomes neutral:

2KOH + H 2 SO 4 → K 2 SO 4 + 2H 2 O.

4. React with salts forming a new salt and base:

2NaOH + CuSO 4 → Cu(OH) 2 + Na 2 SO 4.

5. Able to decompose into water and basic oxide when heated:

Cu (OH) 2 \u003d CuO + H 2 O.

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Before discussing the chemical properties of bases and amphoteric hydroxides, let's clearly define what it is?

1) Bases or basic hydroxides include metal hydroxides in the oxidation state +1 or +2, i.e. the formulas of which are written either as MeOH or as Me(OH) 2 . However, there are exceptions. So, the hydroxides Zn (OH) 2, Be (OH) 2, Pb (OH) 2, Sn (OH) 2 do not belong to the bases.

2) Amphoteric hydroxides include metal hydroxides in the oxidation state +3, +4, and, as exceptions, hydroxides Zn (OH) 2, Be (OH) 2, Pb (OH) 2, Sn (OH) 2. Metal hydroxides in the oxidation state +4 are not found in the USE assignments, therefore they will not be considered.

Chemical properties of bases

All bases are divided into:

Recall that beryllium and magnesium are not alkaline earth metals.

In addition to being soluble in water, alkalis also dissociate very well in aqueous solutions, while insoluble bases have a low degree of dissociation.

This difference in solubility and ability to dissociate between alkalis and insoluble hydroxides leads, in turn, to noticeable differences in their chemical properties. So, in particular, alkalis are more chemically active compounds and are often capable of entering into those reactions that insoluble bases do not enter into.

Reaction of bases with acids

Alkalis react with absolutely all acids, even very weak and insoluble ones. For example:

Insoluble bases react with almost all soluble acids, do not react with insoluble silicic acid:

It should be noted that both strong and weak bases with the general formula of the form Me (OH) 2 can form basic salts with a lack of acid, for example:

Interaction with acid oxides

Alkalis react with all acidic oxides to form salts and often water:

Insoluble bases are able to react with all higher acid oxides corresponding to stable acids, for example, P 2 O 5, SO 3, N 2 O 5, with the formation of medium salts:

Insoluble bases of the form Me (OH) 2 react in the presence of water with carbon dioxide exclusively with the formation of basic salts. For example:

Cu(OH) 2 + CO 2 = (CuOH) 2 CO 3 + H 2 O

With silicon dioxide, due to its exceptional inertness, only the strongest bases, alkalis, react. In this case, normal salts are formed. The reaction does not proceed with insoluble bases. For example:

Interaction of bases with amphoteric oxides and hydroxides

All alkalis react with amphoteric oxides and hydroxides. If the reaction is carried out by fusing an amphoteric oxide or hydroxide with a solid alkali, such a reaction leads to the formation of hydrogen-free salts:

If aqueous solutions of alkalis are used, then hydroxo complex salts are formed:

In the case of aluminum, under the action of an excess of concentrated alkali, instead of the Na salt, the Na 3 salt is formed:

The interaction of bases with salts

Any base reacts with any salt only if two conditions are met simultaneously:

1) solubility of starting compounds;

2) the presence of a precipitate or gas among the reaction products

For example:

Thermal stability of bases

All alkalis, except Ca(OH) 2 , are resistant to heat and melt without decomposition.

All insoluble bases, as well as slightly soluble Ca (OH) 2, decompose when heated. The highest decomposition temperature for calcium hydroxide is about 1000 o C:

Insoluble hydroxides have much lower decomposition temperatures. So, for example, copper (II) hydroxide decomposes already at temperatures above 70 o C:

Chemical properties of amphoteric hydroxides

Interaction of amphoteric hydroxides with acids

Amphoteric hydroxides react with strong acids:

Amphoteric metal hydroxides in the +3 oxidation state, i.e. type Me (OH) 3, do not react with acids such as H 2 S, H 2 SO 3 and H 2 CO 3 due to the fact that salts that could be formed as a result of such reactions are subject to irreversible hydrolysis to the original amphoteric hydroxide and corresponding acid:

Interaction of amphoteric hydroxides with acid oxides

Amphoteric hydroxides react with higher oxides, which correspond to stable acids (SO 3, P 2 O 5, N 2 O 5):

Amphoteric metal hydroxides in the +3 oxidation state, i.e. type Me (OH) 3, do not react with acid oxides SO 2 and CO 2.

Interaction of amphoteric hydroxides with bases

Of the bases, amphoteric hydroxides react only with alkalis. In this case, if an aqueous solution of alkali is used, then hydroxo complex salts are formed:

And when amphoteric hydroxides are fused with solid alkalis, their anhydrous analogues are obtained:

Interaction of amphoteric hydroxides with basic oxides

Amphoteric hydroxides react when fused with oxides of alkali and alkaline earth metals:

Thermal decomposition of amphoteric hydroxides

All amphoteric hydroxides are insoluble in water and, like any insoluble hydroxides, decompose when heated to the corresponding oxide and water.