Metal in the voltage series after H 2

Metal sulfate in max s.d.

+
+ +

Metal (other)

+
+ +

HNO 3 concentrated

Metal nitrate in max s.d.

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

Metal nitrate

la in max s.o.

+
+

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

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

from conditions

+

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

Fig.2. INTERACTION OF ACIDS WITH METALS

SALT

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.

Insoluble base: copper hydroxide

Foundations- called electrolytes, in the solutions of which there are no anions, except for hydroxide ions (anions are ions that have a negative charge, in this case they are OH - ions). Titles grounds consists of three parts: words hydroxide , to which the name of the metal is added (in the genitive case). For example, copper hydroxide(Cu(OH) 2). For some grounds old names may be used, for example sodium hydroxide(NaOH) - sodium alkali.

Sodium hydroxide, sodium hydroxide, sodium alkali, caustic soda- all this is the same substance, the chemical formula of which is NaOH. Anhydrous sodium hydroxide is a white crystalline substance. A solution is a clear liquid that looks indistinguishable from water. Be careful when using! Caustic soda burns the skin severely!

The classification of bases is based on their ability to dissolve in water. Some properties of bases depend on solubility in water. So, grounds that are soluble in water are called alkali. These include sodium hydroxides(NaOH), potassium hydroxide(KOH), lithium (LiOH), sometimes they are added to their number and calcium hydroxide(Ca (OH) 2)), although in fact it is a slightly soluble white substance (slaked lime).

Getting the grounds

Getting the grounds and alkalis can be done in various ways. To receive alkalis You can use the chemical interaction of metal with water. Such reactions proceed with a very large release of heat, up to ignition (ignition occurs due to the release of hydrogen during the reaction).

2Na + 2H 2 O → 2NaOH + H 2

CaO + H 2 O → Ca (OH) 2

But in industry, these methods have not found practical value, of course, except for the production of calcium hydroxide Ca (OH) 2. Receipt sodium hydroxide and potassium hydroxide associated with the use of electricity. During the electrolysis of an aqueous solution of sodium or potassium chloride, hydrogen is released at the cathode, and chlorine at the anode, while in the solution where the electrolysis occurs, accumulates alkali!

KCl + 2H 2 O → 2KOH + H 2 + Cl 2 (this reaction takes place when an electric current is passed through the solution).

Insoluble bases besiege alkalis from solutions of the corresponding salts.

CuSO 4 + 2NaOH → Cu(OH) 2 + Na 2 SO 4

Base properties

alkalis heat resistant. Sodium hydroxide you can melt and bring the melt to a boil, while it will not decompose. alkalis easily react with acids, resulting in the formation of salt and water. This reaction is also called the neutralization reaction.

KOH + HCl → KCl + H2O

alkalis interact with acidic oxides, as a result of which salt and water are formed.

2NaOH + CO 2 → Na 2 CO 3 + H 2 O

Insoluble bases, unlike alkalis, are not thermally stable substances. Some of them, for example, copper hydroxide, decompose when heated,

Cu(OH) 2 + CuO → H 2 O
others - even at room temperature (for example, silver hydroxide - AgOH).

Insoluble bases interact with acids, the reaction occurs only if the salt that is formed during the reaction dissolves in water.

Cu(OH) 2 + 2HCl → CuCl 2 + 2H 2 O

Alkali metals are metals that react with water to form alkali. Sodium Na is a typical representative of alkali metals. Sodium is lighter than water, so its chemical reaction with water occurs on its surface. Actively dissolving in water, sodium displaces hydrogen from it, while forming sodium alkali (or sodium hydroxide) - caustic soda NaOH. The reaction proceeds as follows:

2Na + 2H 2 O → 2NaOH + H 2

All alkali metals behave in a similar way. If, before starting the reaction, the indicator phenolphthalein is added to the water, and then a piece of sodium is dipped into the water, then the sodium will slide through the water, leaving behind a bright pink trace of the formed alkali (the alkali turns phenolphthalein pink)

iron hydroxide

iron hydroxide is the basis. Iron, depending on the degree of its oxidation, forms two different bases: iron hydroxide, where iron can have valencies (II) - Fe (OH) 2 and (III) - Fe (OH) 3. Like the bases formed by most metals, both iron bases are insoluble in water.

iron hydroxide(II) - white gelatinous substance (precipitate in solution), which has strong reducing properties. Besides, iron hydroxide(II) very unstable. If to a solution iron hydroxide(II) add a little alkali, then a green precipitate will fall out, which darkens rather quickly and turns into a brown precipitate of iron (III).

iron hydroxide(III) has amphoteric properties, but its acidic properties are much less pronounced. Get iron hydroxide(III) is possible as a result of a chemical exchange reaction between an iron salt and an alkali. for example

Fe 2 (SO 4) 3 + 6 NaOH → 3 Na 2 SO 4 +2 Fe (OH) 3

Bases are complex compounds that include two main structural components:

1. Hydroxo group (one or more). Hence, by the way, the second name of these substances is “hydroxides”.
2. Metal atom or ammonium ion (NH4+).

The name of the base comes from the combination of the names of both of its components: for example, calcium hydroxide, copper hydroxide, silver hydroxide, etc.

The only exception to the general rule for the formation of bases should be considered when the hydroxo group is attached not to the metal, but to the ammonium cation (NH4 +). This substance is formed when ammonia dissolves in water.

If we talk about the properties of bases, then it should immediately be noted that the valence of the hydroxo group is equal to one, respectively, the number of these groups in the molecule will directly depend on what valency the metals that enter into the reaction have. Examples in this case are the formulas of such substances as NaOH, Al(OH)3, Ca(OH)2.

The chemical properties of bases are manifested in their reactions with acids, salts, other bases, as well as in their action on indicators. In particular, alkalis can be determined by exposing a certain indicator to their solution. In this case, it will noticeably change its color: for example, it will become blue from white, and phenolphthalein will become crimson.

The chemical properties of bases, manifested in their interaction with acids, lead to the famous neutralization reactions. The essence of such a reaction is that the metal atoms, joining the acid residue, form a salt, and the hydroxo group and the hydrogen ion, when combined, turn into water. This reaction is called a neutralization reaction because no alkali or acid remains after it.

The characteristic chemical properties of bases are also manifested in their reaction with salts. It should be noted that only alkalis react with soluble salts. The structural features of these substances lead to the fact that as a result of the reaction a new salt and a new, most often insoluble, base are formed.

Finally, the chemical properties of the bases perfectly manifest themselves during thermal exposure to them - heating. Here, when carrying out certain experiments, it should be borne in mind that almost all bases, with the exception of alkalis, behave extremely unstable when heated. The vast majority of them almost instantly decomposes into the corresponding oxide and water. And if we take the bases of such metals as silver and mercury, then under normal conditions they cannot be obtained, since they begin to decompose already at room temperature.

Foundations – complex substances that consist of a metal cation Me + (or a metal-like cation, for example, an ammonium ion NH 4 +) and a hydroxide anion OH -.

Based on their solubility in water, bases are divided into soluble (alkali) and insoluble bases . Also have unstable grounds that spontaneously decompose.

Getting the grounds

1. Interaction of basic oxides with water. At the same time, they react with water under normal conditions only those oxides that correspond to a soluble base (alkali). Those. this way you can only get alkalis:

basic oxide + water = base

for example , sodium oxide forms in water sodium hydroxide(sodium hydroxide):

Na 2 O + H 2 O → 2NaOH

At the same time about copper(II) oxide with water does not react:

CuO + H 2 O ≠

2. Interaction of metals with water. Wherein react with waterunder normal conditionsonly alkali metals(lithium, sodium, potassium, rubidium, cesium), calcium, strontium and barium.In this case, a redox reaction occurs, hydrogen acts as an oxidizing agent, and a metal acts as a reducing agent.

metal + water = alkali + hydrogen

for example, potassium reacts with water very violent:

2K 0 + 2H 2 + O → 2K + OH + H 2 0

3. Electrolysis of solutions of some alkali metal salts. As a rule, to obtain alkalis, electrolysis is subjected to solutions of salts formed by alkali or alkaline earth metals and anoxic acids (except hydrofluoric) - chlorides, bromides, sulfides, etc. This issue is discussed in more detail in the article .

for example , electrolysis of sodium chloride:

2NaCl + 2H 2 O → 2NaOH + H 2 + Cl 2

4. Bases are formed by the interaction of other alkalis with salts. In this case, only soluble substances interact, and an insoluble salt or an insoluble base should form in the products:

or

lye + salt 1 = salt 2 ↓ + lye

For example: potassium carbonate reacts in solution with calcium hydroxide:

K 2 CO 3 + Ca(OH) 2 → CaCO 3 ↓ + 2KOH

For example: copper (II) chloride reacts in solution with sodium hydroxide. At the same time, it drops blue precipitate of copper(II) hydroxide:

CuCl 2 + 2NaOH → Cu(OH) 2 ↓ + 2NaCl

Chemical properties of insoluble bases

1. Insoluble bases interact with strong acids and their oxides (and some medium acids). At the same time, they form salt and water.

insoluble base + acid = salt + water

insoluble base + acid oxide = salt + water

for example ,copper (II) hydroxide interacts with strong hydrochloric acid:

Cu(OH) 2 + 2HCl = CuCl 2 + 2H 2 O

In this case, copper (II) hydroxide does not interact with acidic oxide weak carbonic acid - carbon dioxide:

Cu(OH) 2 + CO 2 ≠

2. Insoluble bases decompose when heated into oxide and water.

for example, iron (III) hydroxide decomposes into iron (III) oxide and water when calcined:

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

3. Insoluble bases do not interactwith amphoteric oxides and hydroxides.

insoluble base + amphoteric oxide ≠

insoluble base + amphoteric hydroxide ≠

4. Some insoluble bases can act asreducing agents. Reducing agents are bases formed by metals with minimum or intermediate oxidation state, which can increase their oxidation state (iron (II) hydroxide, chromium (II) hydroxide, etc.).

For example , iron (II) hydroxide can be oxidized with atmospheric oxygen in the presence of water to iron (III) hydroxide:

4Fe +2 (OH) 2 + O 2 0 + 2H 2 O → 4Fe +3 (O -2 H) 3

Chemical properties of alkalis

1. Alkalis interact with any acids - both strong and weak . In this case, salt and water are formed. These reactions are called neutralization reactions. Possibly education acid salt, if the acid is polybasic, at a certain ratio of reagents, or in excess acid. AT excess alkali average salt and water are formed:

alkali (excess) + acid \u003d medium salt + water

alkali + polybasic acid (excess) = acid salt + water

for example , sodium hydroxide, when interacting with tribasic phosphoric acid, can form 3 types of salts: dihydrophosphates, phosphates or hydrophosphates.

In this case, dihydrophosphates are formed in an excess of acid, or at a molar ratio (the ratio of the amounts of substances) of the reagents 1:1.

NaOH + H 3 PO 4 → NaH 2 PO 4 + H 2 O

With a molar ratio of the amount of alkali and acid of 2: 1, hydrophosphates are formed:

2NaOH + H 3 PO 4 → Na 2 HPO 4 + 2H 2 O

In excess of alkali, or at a molar ratio of alkali and acid of 3:1, an alkali metal phosphate is formed.

3NaOH + H 3 PO 4 → Na 3 PO 4 + 3H 2 O

2. Alkalis interact withamphoteric oxides and hydroxides. Wherein common salts are formed in the melt , a in solution - complex salts .

alkali (melt) + amphoteric oxide = medium salt + water

lye (melt) + amphoteric hydroxide = medium salt + water

alkali (solution) + amphoteric oxide = complex salt

alkali (solution) + amphoteric hydroxide = complex salt

for example , when aluminum hydroxide reacts with sodium hydroxide in the melt sodium aluminate is formed. The more acidic hydroxide forms an acid residue:

NaOH + Al(OH) 3 = NaAlO 2 + 2H 2 O

BUT in solution a complex salt is formed:

NaOH + Al(OH) 3 = Na

Pay attention to how the formula of a complex salt is compiled:first we choose the central atom (toas a rule, it is a metal from amphoteric hydroxide).Then add to it ligands- in our case, these are hydroxide ions. The number of ligands is, as a rule, 2 times greater than the oxidation state of the central atom. But the aluminum complex is an exception, its number of ligands is most often 4. We enclose the resulting fragment in square brackets - this is a complex ion. We determine its charge and add the required number of cations or anions from the outside.

3. Alkalis interact with acidic oxides. It is possible to form sour or medium salt, depending on the molar ratio of alkali and acid oxide. In excess of alkali, an average salt is formed, and in an excess of acidic oxide, an acid salt is formed:

alkali (excess) + acid oxide \u003d medium salt + water

or:

alkali + acid oxide (excess) = acid salt

for example , when interacting excess sodium hydroxide With carbon dioxide, sodium carbonate and water are formed:

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

And when interacting excess carbon dioxide with sodium hydroxide, only sodium bicarbonate is formed:

2NaOH + CO 2 = NaHCO 3

4. Alkalis interact with salts. alkalis react only with soluble salts in solution, provided that products form gas or precipitate . These reactions proceed according to the mechanism ion exchange.

alkali + soluble salt = salt + corresponding hydroxide

Alkalis interact with solutions of metal salts, which correspond to insoluble or unstable hydroxides.

for example, sodium hydroxide interacts with copper sulfate in solution:

Cu 2+ SO 4 2- + 2Na + OH - = Cu 2+ (OH) 2 - ↓ + Na 2 + SO 4 2-

Also alkalis interact with solutions of ammonium salts.

for example , potassium hydroxide interacts with ammonium nitrate solution:

NH 4 + NO 3 - + K + OH - \u003d K + NO 3 - + NH 3 + H 2 O

! When salts of amphoteric metals interact with an excess of alkali, a complex salt is formed!

Let's look at this issue in more detail. If the salt formed by the metal to which amphoteric hydroxide , interacts with a small amount of alkali, then the usual exchange reaction proceeds, and precipitatesthe hydroxide of this metal .

for example , excess zinc sulfate reacts in solution with potassium hydroxide:

ZnSO 4 + 2KOH \u003d Zn (OH) 2 ↓ + K 2 SO 4

However, in this reaction, not a base is formed, but mphoteric hydroxide. And, as we mentioned above, amphoteric hydroxides dissolve in an excess of alkalis to form complex salts . T Thus, during the interaction of zinc sulfate with excess alkali solution a complex salt is formed, no precipitate is formed:

ZnSO 4 + 4KOH \u003d K 2 + K 2 SO 4

Thus, we obtain 2 schemes for the interaction of metal salts, which correspond to amphoteric hydroxides, with alkalis:

amphoteric metal salt (excess) + alkali = amphoteric hydroxide↓ + salt

amph.metal salt + alkali (excess) = complex salt + salt

5. Alkalis interact with acidic salts.In this case, medium salts or less acidic salts are formed.

sour salt + alkali \u003d medium salt + water

for example , Potassium hydrosulfite reacts with potassium hydroxide to form potassium sulfite and water:

KHSO 3 + KOH \u003d K 2 SO 3 + H 2 O

It is very convenient to determine the properties of acid salts by mentally breaking an acid salt into 2 substances - an acid and a salt. For example, we break sodium bicarbonate NaHCO 3 into uric acid H 2 CO 3 and sodium carbonate Na 2 CO 3 . The properties of bicarbonate are largely determined by the properties of carbonic acid and the properties of sodium carbonate.

6. Alkalis interact with metals in solution and melt. In this case, a redox reaction occurs, in the solution complex salt and hydrogen, in the melt - medium salt and hydrogen.

Note! Only those metals react with alkalis in solution, in which the oxide with the minimum positive oxidation state of the metal is amphoteric!

for example , iron does not react with an alkali solution, iron (II) oxide is basic. BUT aluminum dissolves in an aqueous solution of alkali, aluminum oxide is amphoteric:

2Al + 2NaOH + 6H 2 + O = 2Na + 3H 2 0

7. Alkalis interact with non-metals. In this case, redox reactions take place. Usually, non-metals disproportionate in alkalis. do not react with alkalis oxygen, hydrogen, nitrogen, carbon and inert gases (helium, neon, argon, etc.):

NaOH + O 2 ≠

NaOH + N 2 ≠

NaOH+C≠

Sulfur, chlorine, bromine, iodine, phosphorus and other non-metals disproportionate in alkalis (i.e. self-oxidize-self-repair).

For example, chlorinewhen interacting with cold alkali goes into oxidation states -1 and +1:

2NaOH + Cl 2 0 \u003d NaCl - + NaOCl + + H 2 O

Chlorine when interacting with hot lye goes into oxidation states -1 and +5:

6NaOH + Cl 2 0 \u003d 5NaCl - + NaCl + 5 O 3 + 3H 2 O

Silicon oxidized by alkalis to an oxidation state of +4.

for example, in solution:

2NaOH + Si 0 + H 2 + O \u003d NaCl - + Na 2 Si + 4 O 3 + 2H 2 0

Fluorine oxidizes alkalis:

2F 2 0 + 4NaO -2 H \u003d O 2 0 + 4NaF - + 2H 2 O

You can read more about these reactions in the article.

8. Alkalis do not decompose when heated.

The exception is lithium hydroxide:

2LiOH \u003d Li 2 O + H 2 O

Alkali metal hydroxides - under normal conditions, they are solid white crystalline substances, hygroscopic, soapy to the touch, very soluble in water (their dissolution is an exothermic process), fusible. Hydroxides of alkaline earth metals Ca (OH) 2, Sr (OH) 2, Ba (OH) 2) are white powdery substances, much less soluble in water compared to alkali metal hydroxides. Water-insoluble bases usually form as gel-like precipitates that decompose on storage. For example, Cu (OH) 2 is a blue gelatinous precipitate.

3.1.4 Chemical properties of bases.

The properties of bases are due to the presence of OH - ions. There are differences in the properties of alkalis and water-insoluble bases, but the common property is the reaction of interaction with acids. The chemical properties of the bases are presented in table 6.

Table 6 - Chemical properties of bases

3.1.5 Essential foundations.

NaOH- caustic soda, caustic soda. Fusible (t pl = 320 °C) white hygroscopic crystals, highly soluble in water. The solution is soapy to the touch and is a dangerous caustic liquid. NaOH is one of the most important products of the chemical industry. It is required in large quantities for the purification of petroleum products, it is widely used in soap, paper, textile and other industries, as well as for the production of artificial fiber.

KOH- caustic potash. White hygroscopic crystals, highly soluble in water. The solution is soapy to the touch and is a dangerous caustic liquid. The properties of KOH are similar to those of NaOH, but potassium hydroxide is used much less frequently due to its higher cost.

Ca(OH) 2 - slaked lime. White crystals, slightly soluble in water. The solution is called “lime water”, the suspension is called “milk of lime”. Lime water is used to recognize carbon dioxide, it becomes cloudy when CO 2 is passed through. Hydrated lime is widely used in the construction industry as a basis for the manufacture of binders.