Metal in a series of stress after Н 2

Metal sulfate in max s.o.

+
+ +

Metal (rest)

+
+ +

HNO 3 concentrate

Metal nitrate in max s.d.

Metal (rest; Al, Cr, Fe, Co, Ni when heated)

Nitrate metal

la in max s.o.

+
+

Metal (the rest in the yard stresses up to H 2)

NO / N 2 O / N 2 / NH 3 (NH 4 NO 3)

on conditions

+

Metal (the rest in the series of stresses after H 2)

Fig. 2. INTERACTION OF ACIDS WITH METALS

SALTS

Salts -these are complex substances that dissociate in solutions with the formation of positively charged ions (cations - basic residues), with the exception of hydrogen ions, and negatively charged ions (anions - acid residues), other than hydroxides - ions.

a) obtaining grounds.

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

CuSO 4 + 2 KOH \u003d Cu (OH) 2  + K 2 SO 4,

K 2 CO 3 + Ba (OH) 2 \u003d 2KON + BaCO 3 .

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

2) Alkalis can also be obtained by the interaction of alkali and alkaline earth metals or their oxides with water:

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

SrO + H 2 O \u003d Sr (OH) 2.

3) Alkalis in technology are usually obtained by electrolysis of aqueous solutions of chlorides:

b)chemical properties of bases.

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

NaOH + HNO 3 \u003d NaNO 3 + H 2 O,

Cu (OH) 2 + H 2 SO 4 \u003d СuSО 4 + 2 H 2 O.

2) It was shown above how alkalis interact with acidic and amphoteric oxides.

3) When alkalis interact with soluble salts, a new salt and a new base are formed. Such a reaction proceeds to the end only when at least one of the obtained substances precipitates.

FeCl 3 + 3 KOH \u003d Fe (OH) 3  + 3 KCl

4) When heated, most bases, with the exception of alkali metal hydroxides, decompose into the corresponding oxide and water:

2 Fe (OH) 3 \u003d Fe 2 O 3 + 3 H 2 O,

Ca (OH) 2 \u003d CaO + H 2 O.

ACIDS -complex substances, the molecules of which consist of one or more hydrogen atoms and an acid residue. The composition of acids can be expressed by the general formula H x A, where A is an acid residue. Hydrogen atoms in acids are capable of being replaced or exchanged for metal atoms, thus forming salts.

If the acid contains one such hydrogen atom, then it is a monobasic acid (HCl - hydrochloric, HNO 3 - nitric, HClO - hypochlorous, CH 3 COOH - acetic); two hydrogen atoms - dibasic acids: H 2 SO 4 - sulfuric, H 2 S - hydrogen sulfide; three hydrogen atoms are tribasic: H 3 PO 4 - orthophosphoric, H 3 AsO 4 - orthoarsenic.

Depending on the composition of the acidic residue, acids are subdivided into oxygen-free (H 2 S, HBr, HI) and oxygen-containing (H 3 PO 4, H 2 SO 3, H 2 CrO 4). In the molecules of oxygen-containing acids, hydrogen atoms are linked through oxygen to the central atom: H - O - E. The names of anoxic acids are formed from the root of the Russian name for a non-metal, a connecting vowel - about- and the words "hydrogen" (H 2 S - hydrogen sulfide). The names of oxygen-containing acids are given as follows: if a non-metal (less often a metal) that is part of the acid residue is in the highest oxidation state, then suffixes are added to the root of the Russian name of the element -n-, -ev-, or - ov- and further ending -and I- (H 2 SO 4 - sulfuric, H 2 CrO 4 - chrome). If the oxidation state of the central atom is lower, then the suffix -ist-(H 2 SO 3 - sulphurous). If the non-metal forms a number of acids, use other suffixes (HClO - chlorine ovistah, HClO 2 - chlorine istah, HClO 3 - chlorine ovateah, HClO 4 - chlorine nand I).

FROM
from the point of view of the theory of electrolytic dissociation, acids are electrolytes that dissociate in an aqueous solution with the formation of only hydrogen ions as cations:

H x A xH + + A x-

The presence of H + ions caused a change in the color of indicators in acid solutions: litmus (red), methyl orange (pink).

Obtaining and properties of acids

and) obtaining acids.

1) Anoxic acids can be obtained by direct combination of non-metals with hydrogen and subsequent dissolution of the corresponding gases in water:

2) Oxygen-containing acids can often be obtained by the interaction of acid oxides with water.

3) Both anoxic and oxygen-containing acids can be obtained by exchange reactions between salts and other acids:

BaBr 2 + H 2 SO 4 \u003d BaSO 4  + 2 HBr,

CuSO 4 + H 2 S \u003d H 2 SO 4 + CuS ,

FeS + H 2 SO 4 (par.) \u003d H 2 S  + FeSO 4,

NaCl (solid) + H 2 SO 4 (conc.) \u003d HCl  + NaHSO 4,

AgNO 3 + HCl \u003d AgCl  + HNO 3,

4) In a number of cases, redox reactions can be used to obtain acids:

3P + 5HNO 3 + 2H 2 O \u003d 3H 3 PO 4 + 5NO 

b ) chemical properties of acids.

1) Acids interact with bases and amphoteric hydroxides. In this case, practically insoluble acids (H 2 SiO 3, H 3 BO 3) can react only with soluble alkalis.

H 2 SiO 3 + 2NaOH \u003d Na 2 SiO 3 + 2H 2 O

2) The interaction of acids with basic and amphoteric oxides is discussed above.

3) The interaction of acids with salts is an exchange reaction with the formation of salt and water. This reaction goes to the end if the reaction product is an insoluble or volatile substance, or a weak electrolyte.

Ni 2 SiO 3 + 2HCl \u003d 2NaCl + H 2 SiO 3

Na 2 CO 3 + H 2 SO 4 \u003d Na 2 SO 4 + H 2 O + CO 2 

4) The interaction of acids with metals is a redox process. Reducing agent - metal, oxidizing agent - hydrogen ions (non-oxidizing acids: HCl, HBr, HI, H 2 SO 4 (diluted), H 3 PO 4) or anion of an acid residue (acid-oxidizing agents: H 2 SO 4 (conc.), HNO 3 (end and split)). The products of the reaction of the interaction of non-oxidizing acids with metals, standing in a series of voltages up to hydrogen, are salt and gaseous hydrogen:

Zn + H 2 SO 4 (diluted) \u003d ZnSO 4 + H 2 

Zn + 2HCl \u003d ZnCl 2 + H 2 

Oxidizing acids interact with almost all metals, including low-activity ones (Cu, Hg, Ag), and the products of the acid anion reduction, salt and water are formed:

Cu + 2H 2 SO 4 (conc.) \u003d CuSO 4 + SO 2  + 2 H 2 O,

Pb + 4НNО 3 (conc) \u003d Pb (NO 3) 2 + 2NO 2  + 2Н 2 O

AMPHOTERIC HYDROXIDESshow acid-base duality: they react with acids as bases:

2Cr (OH) 3 + 3H 2 SO 4 \u003d Cr 2 (SO 4) 3 + 6H 2 O,

and with bases - as acids:

Cr (OH) 3 + NaOH \u003d Na (the reaction proceeds in an alkali solution);

Cr (OH) 3 + NaOH \u003d NaCrO 2 + 2H 2 O (the reaction proceeds between solids during fusion).

Amphoteric hydroxides form salts with strong acids and bases.

Like other insoluble hydroxides, amphoteric hydroxides decompose when heated into oxide and water:

Be (OH) 2 \u003d BeO + H 2 O.

SALTS - ionic compounds, consisting of metal cations (or ammonium) and anions of acid residues. Any salt can be considered as a product of a base neutralization reaction with an acid. Depending on the ratio of acid and base taken, salts are obtained: average (ZnSO 4, MgCl 2) - the product of complete neutralization of the base with acid, sour (NaHCO 3, KH 2 PO 4) - with an excess of acid, the main(CuOHCl, AlOHSO 4) - with an excess of base.

According to the international nomenclature, the names of salts are formed from two words: the names of the acid anion in the nominative case and the metal cation in the genitive, indicating its oxidation state, if it is a variable, in Roman numerals in brackets. For example: Cr 2 (SO 4) 3 - chromium (III) sulfate, AlCl 3 - aluminum chloride. The names of acidic salts are formed by the addition of the word hydro-or dihydro- (depending on the number of hydrogen atoms in the hydroanion): Ca (HCO 3) 2 - calcium bicarbonate, NaH 2 PO 4 - sodium dihydrogen phosphate. The names of basic salts are formed by the addition of the word hydroxy or dihydroxo : (AlOH) Cl 2 - aluminum hydroxochloride, 2 SO 4 - chromium (III) dihydroxosulfate.

Obtaining and properties of salts

and ) chemical properties of salts.

1) The interaction of salts with metals is a redox process. In this case, the metal standing to the left in the electrochemical series of voltages displaces the following ones from the solutions of their salts:

Zn + CuSO 4 \u003d ZnSO 4 + Cu

Alkali and alkaline earth metals are not used to reduce other metals from aqueous solutions of their salts, since they interact with water, displacing hydrogen:

2Na + 2H 2 O \u003d H 2  + 2NaOH.

2) The interaction of salts with acids and alkalis was discussed above.

3) The interaction of salts with each other in a solution is irreversible only if one of the products is a poorly soluble substance:

BaCl 2 + Na 2 SO 4 \u003d BaSO 4  + 2NaCl.

4) Hydrolysis of salts - the exchange decomposition of some salts with water. Hydrolysis of salts will be discussed in detail in the topic "electrolytic dissociation".

b) methods of obtaining salts.

In laboratory practice, the following methods of obtaining salts are usually used, based on the chemical properties of various classes of compounds and simple substances:

1) Interaction of metals with non-metals:

Cu + Cl 2 \u003d CuCl 2,

2) Interaction of metals with salt solutions:

Fe + CuCl 2 \u003d FeCl 2 + Cu.

3) Interaction of metals with acids:

Fe + 2HCl \u003d FeCl 2 + H 2 .

4) Interaction of acids with bases and amphoteric hydroxides:

3HCl + Al (OH) 3 \u003d AlCl 3 + 3H 2 O.

5) Interaction of acids with basic and amphoteric oxides:

2HNO 3 + CuO \u003d Cu (NO 3) 2 + 2H 2 O.

6) Interaction of acids with salts:

HCl + AgNO 3 \u003d AgCl + HNO 3.

7) Interaction of alkalis with salts in solution:

3KOH + FeCl 3 \u003d Fe (OH) 3  + 3KCl.

8) Interaction of two salts in solution:

NaCl + AgNO 3 \u003d NaNO 3 + AgCl.

9) Interaction of alkalis with acidic and amphoteric oxides:

Ca (OH) 2 + CO 2 \u003d CaCO 3 + H 2 O.

10) Interaction of oxides of different nature with each other:

CaO + CO 2 \u003d CaCO 3.

Salts occur naturally in the form of minerals and rocks, dissolved in the water of the oceans and seas.

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. whose formulas are written either as MeOH, or as Me (OH) 2. However, there are exceptions. So, hydroxides Zn (OH) 2, Be (OH) 2, Pb (OH) 2, Sn (OH) 2 do not belong to bases.

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

Chemical properties of bases

All bases are subdivided into:

Recall that beryllium and magnesium are not alkaline earth metals.

In addition to being water-soluble, 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 in 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 in which insoluble bases do not enter.

Interaction of bases with acids

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

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 a general formula of the form Me (OH) 2 can form basic salts with a lack of acid, for example:

Interaction with acidic oxides

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

Insoluble bases are capable of reacting 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 salts1:

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

Cu (OH) 2 + CO 2 \u003d (CuOH) 2 CO 3 + H 2 O

Due to its exceptional inertness, only the strongest bases - alkalis - react with silicon dioxide. This produces normal salts. The reaction does not proceed with insoluble bases. For instance:

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, this reaction leads to the formation of anhydrous salts:

If aqueous solutions of alkalis are used, then hydroxocomplex 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:

Interaction of bases with salts

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

1) the solubility of the starting compounds;

2) the presence of sediment or gas among the reaction products

For instance:

Thermal stability of bases

All alkalis, except for 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. Most heat decomposition of calcium hydroxide - 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. species 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 form as a result of such reactions are subject to irreversible hydrolysis to the initial amphoteric hydroxide and corresponding acid:

Interaction of amphoteric hydroxides with acidic 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 acidic 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 hydroxocomplex salts are formed:

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

Reaction of amphoteric hydroxides with basic oxides

Amphoteric hydroxides react by fusion 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 on heating into the corresponding oxide and water.