Hydroxides are called complex substances containing an 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(bases) (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 ionic-covalent bond type 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 predominantly covalent bonds.

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

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

Acid hydroxides (oxoacids) in aqueous solutions 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 are generally 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 hydronium 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 + = H 2 O

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

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

HIO + NaOH = NaIO + H2O

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

Al(OH) 3¯ + 3NaOH = Na 3

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

Al(OH) 3 ¯ + NaOH (melt) = 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 - 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 of basic and amphoteric hydroxides are 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 with 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 conventionally written as NH 3 ×H 2 O and are 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 the 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 their corresponding oxides.

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

12. Give reactions demonstrating 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 constructed according to the rules of nomenclature for complex compounds, which will be discussed below. At the same time, they are widely used in domestic practice traditional names common oxoacids - carbonic, sulfuric, phosphoric, etc. Their use is permissible, but only for a limited range of the 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. Acid name formed from Russian name for acid-forming element(if the element name contains the ending “th”, “o”, “a”, then it is omitted) with the addition, depending on the degree of oxidation of the element, of various endings(Table 1.3, 1.4). Traditionally, H 2 CO 3 is called coal, and not carbonic acid.

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

As can be seen from table. 1.2, for highest oxidation state of element N the name of the acid is formed by adding endings to the name of most elements: -naya, -evaya And –ovaya . For arsenic and antimony, according to the rules of the Russian language, endings are used -yannaya And –yana. Name of acids with the oxidation state of the element N-2 formed mainly formed by ending -tired (for sulfur, arsenic and antimony: -low, -ovous And – yangy ). Acids formed by elements with the lowest oxidation states N-4, have endings –newish . For phosphorous H 2 PHO 3 and hypophosphorous HPH 2 O 2 acids, characterized by a specific structure due to the presence of pH bonds, it is recommended to use special names - phosphonic and phosphinic.

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

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

N	E z+	Ending	Acid name
III	B 3+	-naya	H3BO3 ortho boron Naya HBO 2 meta boron Naya,H 2 B 4 O 7 tetra boron Naya
Al 3+	-evaya	H3AlO3 ortho aluminum eva, HAlO 2 meta-aluminum eva
IV	C 4+	-naya	H 2 CO 3 coal
Si 4+	-evaya	H4SiO4 ortho flints eva, H 2 SiO 3 meta flints eva
Ge 4+	-evaya	H4GeO4 ortho germany eva, H 2 GeO 3 meta germany eva
Sn 4+	-yannaya	H4SnO4 ortho olo withered, H 2 SnO 3 meta tins yannaya
V	N 5+	-naya	HNO 3 nitrogen Naya
P5+	-naya	H3PO4 ortho phosphorus Naya, HPO 3 meta phosphorus Naya, H4P2O7 di phosphorus Naya, H5P3O10 three phosphorus Naya
As 5+	-new	H3AsO4 ortho arsenic new, HasO 3 meta arsenic new
Sb 5+	-yana	H3SbO4 ortho antimony, HSbO 3 meta antimony yana
VI	S 6+	-naya	H 2 SO 4 sulfur Naya, H2S2O7 di gray Naya
SE 6+	-new	H 2 SeO 4 selenium new
Te 6+	-new	H6TeO6 ortho tellurium new, H 2 TeO 4 meta telluriumnew
V	N 3+	-tired	HNO 2 nitrogen exhausted
P 3+	-tired	H 2 PHO 3 phosphorus exhausted(phosphonic)
As 3+	-ovous	H3AsO3 ortho arsenic ovous, HasO2 meta arsenic ovous
Sb 3+	-yangy	H3SbO3 ortho antimony yangy, HSbO2 meta antimony yangy
VI	S 4+	-low	H 2 SO 3 sulfur low
SE 4+	-tired	H 2 SeO 3 selenium exhausted
Te 4+	-tired	H 2 TeO 3 tellurium exhausted
V	N+	-newish	H 2 N 2 O 2 nitrogen newish
P+	-newish	HPH 2 O 2 phosphorus newish(phosphine)

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

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 groups III-VII is also determined by the group number N and traditional names of their oxoacids 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 ovaya, H2Cr2O7 di chromium new, HMnO 4 manganese eva. 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 p-elements of group VII.

N	E z+	Ending	Acid name
Highest oxidation state of element N
VII	Cl 7+	-naya	HClO 4 chlorine Naya
Br 7+	HBrO 4 bromine Naya
I 7+	H5IO6 ortho iodine Naya,HIO 4 meta iodine Naya
Oxidation state of element N-2
VII	Cl 5+	-new	HClO 3 chlorine new
Br 5+	HBrO 3 bromine new
I 5+	HIO 3 iodine new
Oxidation state of element N-4
VII	Cl 3+	-tired	HClO 2 chlorine exhausted
Br 3+	HBrO 2 bromine exhausted
I 3+	HIO 2 iodine exhausted
Oxidation state of element N-6
VII	Cl+	-ovate	HClO chlorine newish
Br+	HBrO bromine newish
I+	HIO iodine newish

Exercises:

13. Give the traditional names and graphic formulas of the following oxoacids: 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 oxoacids: hypobromous, iodic, selenic, orthotelluric, metaarsenic, disilicon, metatin, phosphorous (phosphonic), phosphorous (phosphinic), pentaphosphoric, metavanadium.

15. Give reactions demonstrating general methods for preparing oxoacids. Give examples of oxides of elements in intermediate oxidation states that, when reacting 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 the reaction equations.

18. Write reactions demonstrating the acidic nature of the following oxides, name the corresponding acids: 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 the peroxide group –О-О- received the group name peroxoacids . The peroxide group in peroxoacids can replace both the oxygen atom in the hydroxide group and the bridging oxygen atom that combines the atoms of the acid-forming element in polynuclear acid hydroxides:

When writing formulas of peroxyacids, it is recommended to enclose the peroxide group in parentheses and write it on the right side of the formula. Traditional names of peroxoacids are formed from the name of the corresponding oxoacid with the addition of the prefix peroxo- . If a peroxyacid contains several peroxide groups, their quantity 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.

Exercise:

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

9.4. Thioacids, polythionic and other substituted oxoacids*-section for in-depth study.

Oxoacids in which some or all of the oxygen atoms are replaced by sulfur atoms are called thioacids . 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 of thioacids are formed from the name of the corresponding oxoacid with the addition of the prefix thio- ; when replacing two or more oxygen atoms with sulfur atoms, their number is indicated by numerical prefixes: di-, tri-, tetra- etc.

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

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

Acidic hydroxides in which part of the hydroxide groups or oxygen atoms are replaced by other halogen atoms or -NH 2 , =NH groups are called substituted acids. The traditional names of such acids are formed from the name of the corresponding oxoacid with the addition of a prefix made up of the names of the substituting halogen atoms or groups (NH 2 - amide , NH – imide ) and connecting vowel -O. In the formulas of such acids, substituting atoms or groups are placed in last place.

Traditionally, substituted sulfuric acids are called sulfonic acids:

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

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

Exercises:

10. Give the traditional names of substituted oxoacids: 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 graphic formulas of acids: thiosulfuric, trithionic, dithioantimonic, 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 that have halide-like properties, exhibit acidic properties and dissociate to form hydronium ions. They form a family oxygen-free acids.

Systematic name for oxygen-free acids formed from Russian name of the element or special name of the pseudohalide group with the addition of a connecting vowel -O and phrases hydrogen acid:

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

HCN - cyan hydrogen acid, HNCS - thiocyanate hydrogen acid,

HN 3 - azide hydrogen acid (or nitrogen hydrogen acid).

Historically, for aqueous solutions of a number of oxygen-free acids in chemical practice, trivial names(see Appendix 2):

HF - hydrofluoric acid, HCl - hydrochloric acid,

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

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, azide, hydrosulfide, thiocyanate, hydroiodic, hydrocyanic, hydrothiocyanate acid.

Acid halides.

Acid halides are called complex substances that can be considered as products of complete replacement of hydroxide groups in oxoacid molecules with halogen atoms. Thus, acid halides are the final member of a series of sequential transformations of oxoacids upon replacement of hydroxide groups with halogen atoms: oxoacid ® halogenated oxoacid ® acid halide. For example, POCl 3 is the end member of a series of sequential substitution of three hydroxide groups in orthophosphoric acid:

Some acid halides can be considered as derivatives of unstable oxoacids - 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, several methods for constructing their names are used for acid halides. :

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

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

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

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

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

- traditional names formed using numerical prefixes indicating the number of halogen atoms, the Russian name for halogens, the ending – anhydride and the names of the kilote in the genitive case: PCl 3 - phosphorous acid trichloride, POCl 3 - phosphoric acid trichloride, POBrCl 2 - phosphoric acid dichlorobromohydride;

Limited use allowed for sulfuric and sulfurous acid halides special names, in which special names of cations are used: SO 2 2+ - sulfuryl and SO 2+ - 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 hydrohalide and oxo acids:

PCl 5 + 3H 2 O = H 3 PO 4 + 5HCl

POBrCl 2 + 3H 2 O = 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 graphic 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 dichlorobromoiodoanhydride, thionyl fluoride.

Salt.

Salts 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 products of acid-base reactions of the interaction of basic and acidic binary E n X m and polyelement chemical compounds, characterized, respectively, by the predominantly ionic and covalent nature of the E-X chemical bond (Table 1.5) .

Table 1.5. Acid-base salt formation reactions.

Connections	Salt formation reaction
Basic	Acidic
NaF	PF 5	NaF + PF 5 = Na
Na2O	P2O5	3Na 2 O + P 2 O 5 = 2Na 3 Na 2 O + P 2 O 5 = 2Na
Na2S	P 2 S 5	3Na 2 S + P 2 S 5 = 2Na 3 Na 2 S + P 2 S 5 = 2Na
Na3N	P 3 N 5	Na 3 N + P 3 N 5 = Na 4
NaH	AlH3	NaH + AlH3 = Na
NaOH	Al(OH) 3	NaOH + Al(OH) 3 = Na NaOH + Al(OH) 3 = Na + H 2 O
NaNO3	I(NO3)	NaNO 3 + I(NO 3) = Na
NaOH	HNO3	NaOH + HNO 3 = Na + H 2 O
Al(OH) 3	H3PO4	Al(OH) 3 + H 3 PO 4 = Al + 6H 2 O 2Al(OH) 3 + 3H 3 PO 4 = Al 2 3 + 6H 2 O Al(OH) 3 + 3H 3 PO 4 = 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 chemical bond. As a result, in melts and solutions, salts undergo a 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:

Salts with complex cations based on two different metal ions or ammonium ion and 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 -

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

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

NaHS® Na + + HS - , HS - Û H + + S 2-

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

- salts that are the products of complete replacement of hydroxide groups with acid 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 crystal hydrates .

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

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

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

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

Al 2 (HPO 4) 3 + H 3 PO 4 = 2Al(H 2 PO 4) 3

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

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

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

Systematic names of oxoacid salts 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, in chemical practice traditional names are widely used for the most common salts of oxoacids.

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

For halogens in the oxidation state +7, the prefix is ​​used in the name of the anions per- and ending –at ; for oxidation states: +5 – end -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 names of oxoacids to indicate their form, are also retained 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 medium salts of oxoacids is constructed from the name of the anion (a group word -and he omitted) and the Russian name of the cation in the genitive case, indicating in Roman numerals in parentheses its oxidation state (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 groups III-VI.

basic hydroxides Wikipedia, basic hydroxides group
Basic hydroxides- these are complex substances that consist of metal atoms or ammonium ions and hydroxo groups (-OH) and dissociate in an aqueous solution to form OH− anions and cations. The name of the base usually consists of two words: the word "hydroxide" and the name of the metal in the genitive case (or the word "ammonium"). Bases that are highly soluble in water are called alkalis.

• 1 Receipt
• 2 Classification
• 3 Nomenclature
• 4 Chemical properties
• 5 See also
• 6 Literature

Receipt

Sodium hydroxide granules Calcium hydroxide Aluminum hydroxide Iron metahydroxide

• The interaction of a strong base oxide with water produces a strong base or alkali. Weakly basic and amphoteric oxides do not react with water, so the corresponding hydroxides cannot be obtained in this way.
• Hydroxides of low-active metals are obtained by adding alkali to solutions of the corresponding salts. Since the solubility of weakly basic hydroxides in water is very low, the hydroxide precipitates from solution in the form of a gelatinous mass.
• The base can also be obtained by reacting an alkali or alkaline earth metal with water.
• Alkali metal hydroxides are produced industrially by electrolysis of aqueous salt solutions:
• Some bases can be obtained by exchange reactions:
• Metal bases occur in nature in the form of minerals, for example: hydrargillite Al(OH)3, brucite Mg(OH)2.

Classification

The bases are classified according to a number of characteristics.

• According to solubility in water.
  • Soluble bases (alkalis): lithium hydroxide LiOH, sodium hydroxide NaOH, potassium hydroxide KOH, barium hydroxide Ba(OH)2, strontium hydroxide Sr(OH)2, cesium hydroxide CsOH, rubidium hydroxide RbOH.
  • Practically insoluble bases: Mg(OH)2, Ca(OH)2, Zn(OH)2, Cu(OH)2, Al(OH)3, Fe(OH)3, Be(OH)2.
  • Other bases: NH3 H2O

The division into soluble and insoluble bases almost completely coincides with the division into strong and weak bases, or hydroxides of metals and transition elements. The exception is lithium hydroxide LiOH, which is highly soluble in water but is a weak base.

• By the number of hydroxyl groups in the molecule.
  • Monoacid (sodium hydroxide NaOH)
  • Diacid (copper(II) hydroxide Cu(OH)2)
  • Triacid (iron(III) hydroxide Fe(OH)3)

• By volatility.
  • Volatile: NH3, CH3-NH2
  • Non-volatile: alkalis, insoluble bases.

• In terms of stability.
  • Stable: sodium hydroxide NaOH, barium hydroxide Ba(OH)2
  • Unstable: ammonium hydroxide NH3·H2O (ammonia hydrate).

• According to the degree of electrolytic dissociation.
  • Strong (α > 30%): alkalis.
  • Weak (α< 3 %): нерастворимые основания.

• By the presence of oxygen.
  • Oxygen-containing: potassium hydroxide KOH, strontium hydroxide Sr(OH)2
  • Oxygen-free: ammonia NH3, amines.

• By connection type:
  • Inorganic bases: contain one or more -OH groups.
  • Organic bases: organic compounds that are proton acceptors: amines, amidines and other compounds.

Nomenclature

According to IUPAC nomenclature, inorganic compounds containing -OH groups are called hydroxides. Examples of systematic names of hydroxides:

• NaOH - sodium hydroxide
• TlOH - thallium(I) hydroxide
• Fe(OH)2 - iron(II) hydroxide

If a compound contains oxide and hydroxide anions simultaneously, then numerical prefixes are used in the names:

• TiO(OH)2 - titanium dihydroxide-oxide
• MoO(OH)3 - molybdenum trihydroxide-oxide

For compounds containing the O(OH) group, traditional names with the prefix meta- are used:

• AlO(OH) - aluminum metahydroxide
• CrO(OH) - chromium metahydroxide

For oxides hydrated by an indefinite number of water molecules, for example Tl2O3 n H2O, it is unacceptable to write formulas like Tl(OH)3. Such compounds are also called hydroxides Not recommended. Examples of names:

• Tl2O3 n H2O - thallium(III) oxide polyhydrate
• MnO2 n H2O - manganese(IV) oxide polyhydrate

Special mention should be made of the compound NH3 H2O, which was previously written as NH4OH and which exhibits the properties of a base in aqueous solutions. This and similar compounds should be referred to as hydrate:

• NH3 H2O - ammonia hydrate
• N2H4 H2O - hydrazine hydrate

Chemical properties

• In aqueous solutions, bases dissociate, which changes the ionic equilibrium:

this change is evident in the colors of some acid-base indicators:

• litmus turns blue
• methyl orange - yellow,
• phenolphthalein takes on a fuchsia color.

• When interacting with an acid, a neutralization reaction occurs and salt and water are formed:

Note: the reaction does not occur if both the acid and the base are weak.

• If there is an excess of acid or base, the neutralization reaction does not proceed to completion and acidic or basic salts are formed, respectively:

• Amphoteric bases can react with alkalis to form hydroxo complexes:

• Bases react with acidic or amphoteric oxides to form salts:

• Bases enter into exchange reactions (react with salt solutions):

• Weak and insoluble bases decompose when heated into oxide and water:

Some bases (Cu(I), Ag, Au(I)) decompose already at room temperature.

• Alkali metal bases (except lithium) melt when heated; the melts are electrolytes.

see also

• Acid
• Oxides
• Hydroxides
• Theories of acids and bases

Literature

• Chemical Encyclopedia / Editorial Board: Knunyants I.L. and others. - M.: Soviet Encyclopedia, 1988. - T. 1. - 623 p.
• Chemical Encyclopedia / Editorial Board: Knunyants I.L. and others. - M.: Soviet Encyclopedia, 1992. - T. 3. - 639 p. - ISBN 5-82270-039-8.
• Lidin R.A. and others. Nomenclature of inorganic substances. - M.: KolosS, 2006. - 95 p. - ISBN 5-9532-0446-9.

p·o·r Hydroxides

basic hydroxides, basic hydroxides Wikipedia, basic hydroxides of the group, basic hydroxides are

3. Hydroxides

Among multielement compounds, an important group is hydroxides. Some of them exhibit the properties of bases (basic hydroxides) - NaOH, Ba(OH ) 2, etc.; others exhibit the properties of acids (acid hydroxides) - HNO3, H3PO4 and others. There are also amphoteric hydroxides that, depending on conditions, can exhibit both the properties of bases and the properties of acids - Zn (OH) 2, Al (OH) 3, etc.

3.1. Classification, preparation and properties of bases

From the standpoint of the theory of electrolytic dissociation, bases (basic hydroxides) are substances that dissociate in solutions to form OH hydroxide ions - .

According to modern nomenclature, they are usually called hydroxides of elements, indicating, if necessary, the valence of the element (in Roman numerals in brackets): KOH - potassium hydroxide, sodium hydroxide NaOH , calcium hydroxide Ca(OH ) 2, chromium hydroxide ( II)-Cr(OH ) 2, chromium hydroxide ( III) - Cr (OH) 3.

Metal hydroxides usually divided into two groups: water soluble(formed by alkali and alkaline earth metals - Li, Na, K, Cs, Rb, Fr, Ca, Sr, Ba and therefore called alkalis) and insoluble in water. The main difference between them is that the concentration of OH ions - in alkali solutions is quite high, but for insoluble bases it is determined by the solubility of the substance and is usually very small. However, small equilibrium concentrations of the OH ion - even in solutions of insoluble bases, the properties of this class of compounds are determined.

By the number of hydroxyl groups (acidity) , capable of being replaced by an acidic residue, are distinguished:

Mono-acid bases - KOH, NaOH;

Diacid bases - Fe (OH) 2, Ba (OH) 2;

Triacid bases - Al (OH) 3, Fe (OH) 3.

Getting grounds

1. The general method for preparing bases is an exchange reaction, with the help of which both insoluble and soluble bases can be obtained:

CuSO 4 + 2KOH = Cu(OH) 2 ↓ + K 2 SO 4 ,

K 2 SO 4 + Ba(OH) 2 = 2KOH + BaCO 3↓ .

When soluble bases are obtained by this method, an insoluble salt precipitates.

When preparing water-insoluble bases with amphoteric properties, excess alkali should be avoided, since dissolution of the amphoteric base may occur, for example,

AlCl 3 + 3KOH = Al(OH) 3 + 3KCl,

Al(OH) 3 + KOH = K.

In such cases, ammonium hydroxide is used to obtain hydroxides, in which amphoteric oxides do not dissolve:

AlCl 3 + 3NH 4 OH = Al(OH) 3 ↓ + 3NH 4 Cl.

Silver and mercury hydroxides decompose so easily that when trying to obtain them by exchange reaction, instead of hydroxides, oxides precipitate:

2AgNO 3 + 2KOH = Ag 2 O ↓ + H 2 O + 2KNO 3.

2. Alkalis in technology are usually obtained by electrolysis of aqueous solutions of chlorides:

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

(total electrolysis reaction)

Alkalis can also be obtained by reacting alkali and alkaline earth metals or their oxides with water:

2 Li + 2 H 2 O = 2 LiOH + H 2,

SrO + H 2 O = Sr (OH) 2.

Chemical properties of bases

1. All bases insoluble in water decompose when heated to form oxides:

2 Fe (OH) 3 = Fe 2 O 3 + 3 H 2 O,

Ca (OH) 2 = CaO + H 2 O.

2. The most characteristic reaction of bases is their interaction with acids - the neutralization reaction. Both alkalis and insoluble bases enter into it:

NaOH + HNO 3 = NaNO 3 + H 2 O,

Cu(OH) 2 + H 2 SO 4 = CuSO 4 + 2H 2 O.

3. Alkalis interact with acidic and amphoteric oxides:

2KOH + CO 2 = K 2 CO 3 + H 2 O,

2NaOH + Al 2 O 3 = 2NaAlO 2 + H 2 O.

4. Bases can react with acidic salts:

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.

5. It is necessary to especially emphasize the ability of alkali solutions to react with some non-metals (halogens, sulfur, white phosphorus, silicon):

2 NaOH + Cl 2 = NaCl + NaOCl + H 2 O (in the cold),

6 KOH + 3 Cl 2 = 5 KCl + KClO 3 + 3 H 2 O (when heated),

6KOH + 3S = K 2 SO 3 + 2K 2 S + 3H 2 O,

3KOH + 4P + 3H 2 O = PH 3 + 3KH 2 PO 2,

2NaOH + Si + H 2 O = Na 2 SiO 3 + 2H 2.

6. In addition, concentrated solutions of alkalis, when heated, are also capable of dissolving some metals (those whose compounds have amphoteric properties):

2Al + 2NaOH + 6H 2 O = 2Na + 3H 2,

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

Alkaline solutions have a pH> 7 (alkaline environment), change the color of indicators (litmus - blue, phenolphthalein - purple).

M.V. Andryukhova, L.N. Borodina

Hydroxides can be thought of as the product of the addition (real or mental) of water to the corresponding oxides. Hydroxides are divided into bases, acids, and amphoteric hydroxides. Bases have the general composition M(OH)x, acids have the general composition HxCo. In molecules of oxygen-containing acids, the replaced hydrogen atoms are connected to the central element through oxygen atoms. In molecules of oxygen-free acids, hydrogen atoms are attached directly to a non-metal atom. Amphoteric hydroxides include primarily hydroxides of aluminum, beryllium and zinc, as well as hydroxides of many transition metals in intermediate oxidation states.
Based on solubility in water, soluble bases are distinguished - alkalis (formed by alkali and alkaline earth metals). The bases formed by other metals do not dissolve in water. Most inorganic acids are soluble in water. Only silicic acid H2SiO3 is a water-insoluble inorganic acid. Amphoteric hydroxides do not dissolve in water.

Chemical properties of bases.

All bases, both soluble and insoluble, have a common characteristic property - to form salts.
Let's consider the chemical properties of soluble bases (alkalis):
1. When dissolved in water, they dissociate to form a metal cation and a hydroxide anion. Change the color of the indicators: violet litmus - to blue, phenolphthalein - to crimson, methyl orange - to yellow, universal indicator paper - to blue.
2. Interaction with acid oxides:
alkali + acid oxide = salt.
3. Interaction with acids:
alkali + acid = salt + water.
The reaction between an acid and alkali is called a neutralization reaction.
4. Interaction with amphoteric hydroxides:
alkali + amphoteric hydroxide = salt (+ water)
5. Interaction with salts (subject to the solubility of the original salt and the formation of a precipitate or gas as a result of the reaction.
Let's consider the chemical properties of insoluble bases:
1. Interaction with acids:
base + acid = salt + water.
Polyacid bases are capable of forming not only intermediate, but also basic salts.
2. Heat decomposition:
base = metal oxide + water.

Chemical properties of acids.

All acids have a common characteristic property - the formation of salts when replacing hydrogen cations with metal/ammonium cations.
Let's consider the chemical properties of water-soluble acids:
1. When dissolved in water, they dissociate to form hydrogen cations and an acid residue anion. Change the color of the indicators to red (pink), with the exception of phenolphthalein (does not react to acids, remains colorless).
2. Interaction with metals in the activity series to the left of hydrogen (subject to the formation of a soluble salt):
acid + metal = salt + hydrogen.
When interacting with metals, the exceptions are oxidizing acids - nitric and concentrated sulfuric acids. Firstly, they also react with some metals that are to the right of hydrogen in the activity series. Secondly, the reaction with metals never releases hydrogen, but produces a salt of the corresponding acid, water and the reduction products of nitrogen or sulfur, respectively.
3. Interaction with bases/amphoteric hydroxides:
acid + base = salt + water.
4. Interaction with ammonia:
acid + ammonia = ammonium salt
5. Interaction with salts (subject to the formation of gas or sediment):
acid + salt = salt + acid.
Polybasic acids are capable of forming not only intermediate, but also acidic salts.
Insoluble silicic acid does not change the color of indicators (a very weak acid), but is capable of reacting with alkali solutions with slight heating:
1. Interaction of silicic acid with alkali solution:
silicic acid + alkali = salt + water.
2. Decomposition (during long-term storage or heating)
silicic acid = silicon(IV) oxide + water.

Chemical properties of amphoteric hydroxides.

Amphoteric hydroxides are capable of forming two series of salts, since when reacting with alkalis they exhibit the properties of an acid, and when reacting with acids they exhibit the properties of a base.
Let's consider the chemical properties of amphoteric hydroxides:
1. Interaction with alkalis:
amphoteric hydroxide + alkali = salt (+ water).
2. Interaction with acids:
amphoteric hydroxide + acid = salt + water.

Physical properties

The general formula of alkali metal hydroxides is MOH.

All alkali metal hydroxides are colorless, hygroscopic substances that easily dissolve in air, are very soluble in water and ethanol, and solubility increases when moving from LiOH to CsOH.

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 = Li 2 O + H 2 O.

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

NaOH = Na + + OH - .

React with non-metal oxides:

KOH + CO 2 = KHCO 3;

2NaOH + CO 2 = Na 2 CO 3 + H 2 O;

2KOH + 2NO2 = KNO3 + KNO2 + H2O.

They interact with acids and undergo a neutralization reaction:

NaOH + HCl = NaCl + H 2 O;

KOH + HNO 3 = KNO 3 + H 2 O.

They enter into exchange reactions with salts:

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

Reacts with halogens:

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

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

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

2KOH + Zn = 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 = Na 2 + H 2;

2NaOH + BeO + H 2 O = 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, during which hydrogen is released at the cathode and chlorine is formed at the anode:

2NaCl + 2H2OH2 + 2NaOH + Cl2.

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

Rb 2 SO 4 + Ba(OH) 2 = 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°boil. °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 temperatures. and boiling point, ionization potentials, densities and hardness.

Chemical properties

1. Very reactive.

2. They have a positive valence of +2.

3. React with water at room temperature (except Be) to release hydrogen.

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

5. With hydrogen they form salt-like hydrides EH 2.

6. Oxides have the general formula EO. The tendency to form 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 reduction of the oxide:

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; compounds 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 (diluted) ® 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 cations of alkaline earth metals - 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 discovered 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 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. Reacts 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 is an 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 are white crystalline substances, less soluble in water than hydroxides of alkali metals (the solubility of hydroxides decreases with decreasing atomic number; Be(OH) 2 is 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) 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 water. Hard water forms scale when boiled and food products cannot be cooked 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 is due to 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 solution.