OVR in the article is specially highlighted in color. Pay special attention to them. These equations can get caught in the exam.

Dilute sulfuric acid behaves like other acids, hiding its oxidative capabilities:

And one more thing to remember about dilute sulfuric acid: she does not react with lead. A piece of lead thrown into dilute H2SO4 is covered with a layer of insoluble (see solubility table) lead sulfate and the reaction stops immediately.

Oxidizing properties of sulfuric acid

- heavy oily liquid, non-volatile, tasteless and odorless

Due to sulfur in the oxidation state +6 (highest) sulfuric acid acquires strong oxidizing properties.

Rule for task 24 (old A24) when preparing sulfuric acid solutions never pour water into it. Concentrated sulfuric acid should be poured into water in a thin stream, stirring constantly.

The interaction of concentrated sulfuric acid with metals

These reactions are strictly standardized and follow the scheme:

H2SO4(conc.) + metal → metal sulfate + H2O + reduced sulfur product.

There are two nuances:

1) aluminum, iron And chromium do not react with H2SO4 (conc) under normal conditions due to passivation. Need to heat up.

2) C platinum And gold H2SO4 (conc) does not react at all.

Sulfur V concentrated sulfuric acid- oxidizer

• it means that she will recover herself;
• the degree of oxidation to which sulfur will be reduced depends on the metal.

Consider sulfur oxidation state diagram:

• Before -2 sulfur can be reduced only by very active metals - in a series of voltages up to and including aluminum.

The reactions will go like this:

8Li + 5H 2 SO 4( conc .) → 4Li 2 SO 4 + 4H 2 O+H 2 S

4Mg + 5H 2 SO 4( conc .) → 4MgSO 4 + 4H 2 O+H 2 S

8Al + 15H 2 SO 4( conc .) (t) → 4Al 2 (SO 4 ) 3 + 12H 2 O+3H 2 S

• in the interaction of H2SO4 (conc) with metals in a series of voltages after aluminum but before iron, that is, with metals with an average activity, sulfur is reduced to 0 :

3Mn+4H 2 SO 4( conc .) → 3MnSO 4 + 4H 2 O+S↓

2Cr+4H 2 SO 4( conc .) (t) → Cr 2 (SO 4 ) 3 + 4H 2 O+S↓

3Zn + 4H 2 SO 4( conc .) → 3ZnSO 4 + 4H 2 O+S↓

• all other metals starting with iron in a series of voltages (including those after hydrogen, except for gold and platinum, of course), they can only reduce sulfur up to +4. Since these are inactive metals:

2 Fe + 6 H 2 SO 4(conc.) ( t)→ Fe 2 ( SO 4 ) 3 + 6 H 2 O + 3 SO 2

(note that iron oxidizes to +3, the highest possible, highest oxidation state, as it deals with a strong oxidizing agent)

Cu+2H 2 SO 4( conc .) → CuSO 4 + 2H 2 O+SO 2

2Ag + 2H 2 SO 4( conc .) → Ag 2 SO 4 + 2H 2 O+SO 2

Of course, everything is relative. The depth of reduction will depend on many factors: acid concentration (90%, 80%, 60%), temperature, etc. Therefore, it is impossible to accurately predict the products. The table above also has its own percentage of approximation, but you can use it. It is also necessary to remember that in the Unified State Examination, when the product of reduced sulfur is not indicated, and the metal is not particularly active, then, most likely, the compilers mean SO 2. You need to look at the situation and look for clues in the conditions.

SO 2 - this is generally a frequent product of OVR with the participation of conc. sulfuric acid.

H2SO4 (conc) oxidizes some nonmetals(which exhibit reducing properties), as a rule, to the maximum - the highest degree of oxidation (an oxide of this non-metal is formed). Sulfur is also reduced to SO 2:

C+2H 2 SO 4( conc .) → CO 2 + 2H 2 O+2SO 2

2P+5H 2 SO 4( conc .) → P 2 O 5 + 5H 2 O+5SO 2

Freshly formed phosphorus oxide (V) reacts with water, orthophosphoric acid is obtained. Therefore, the reaction is recorded immediately:

2P+5H 2 SO 4( conc ) → 2H 3 PO 4 + 2H 2 O+5SO 2

The same with boron, it turns into orthoboric acid:

2B+3H 2 SO 4( conc ) → 2H 3 BO 3 + 3SO 2

Very interesting is the interaction of sulfur with an oxidation state of +6 (in sulfuric acid) with "another" sulfur (located in another compound). Within the framework of the exam, the interaction of H2SO4 (conc) is considered with sulfur (a simple substance) and hydrogen sulfide.

Let's start with interaction sulfur (a simple substance) with concentrated sulfuric acid. In a simple substance, the oxidation state is 0, in an acid +6. In this OVR, sulfur +6 will oxidize sulfur 0. Let's look at the diagram of sulfur oxidation states:

Sulfur 0 will be oxidized, and sulfur +6 will be reduced, that is, lower the oxidation state. Sulfur dioxide will be emitted:

2 H 2 SO 4(conc.) + S → 3 SO 2 + 2 H 2 O

But in the case of hydrogen sulfide:

Both sulfur (a simple substance) and sulfur dioxide are formed:

H 2 SO 4( conc .) + H 2 S → S↓ + SO 2 + 2H 2 O

This principle can often help in determining an OVR product where the oxidizing agent and reducing agent are the same element, in different oxidation states. The oxidizing agent and reducing agent "go towards each other" on the oxidation state diagram.

H2SO4 (conc), one way or another, interacts with halides. Only here you need to understand that fluorine and chlorine are “themselves with a mustache” and OVR does not leak with fluorides and chlorides, undergoes the usual ion-exchange process, during which gaseous hydrogen halide is formed:

CaCl 2 + H 2 SO 4 (conc.) → CaSO 4 + 2HCl

CaF 2 + H 2 SO 4(conc.) → CaSO 4 + 2HF

But the halogens in the composition of bromides and iodides (as well as in the composition of the corresponding hydrogen halides) are oxidized by it to free halogens. Only now sulfur is reduced in different ways: iodide is a stronger reducing agent than bromide. Therefore, iodide reduces sulfur to hydrogen sulfide, and bromide to sulfur dioxide:

2H 2 SO 4( conc .) + 2NaBr → Na 2 SO 4 + 2H 2 O+SO 2 +Br 2

H 2 SO 4( conc .) + 2HBr → 2H 2 O+SO 2 +Br 2

5H 2 SO 4( conc .) + 8NaI → 4Na 2 SO 4 + 4H 2 O+H 2 S+4I 2 ↓

H 2 SO 4( conc .) + 8HI → 4H 2 O+H 2 S+4I 2 ↓

Hydrogen chloride and hydrogen fluoride (as well as their salts) are resistant to the oxidizing action of H2SO4 (conc).

And finally, the last thing: for concentrated sulfuric acid, this is unique, no one else can do it. She possesses water-removing property.

This allows you to use concentrated sulfuric acid in a variety of ways:

First, the dehydration of substances. Concentrated sulfuric acid takes water away from the substance and it "becomes dry".

Secondly, a catalyst in reactions in which water is split off (for example, dehydration and esterification):

H 3 C–COOH + HO–CH 3 (H 2 SO 4 (conc.)) → H 3 C–C(O)–O–CH 3 + H 2 O

H 3 C–CH 2 –OH (H 2 SO 4 (conc.)) → H 2 C \u003d CH 2 + H 2 O

Physical properties of sulfuric acid:
Heavy oily liquid ("vitriol");
density 1.84 g/cm3; non-volatile, highly soluble in water - with strong heating; t°pl. = 10.3°C, bp \u003d 296 ° C, very hygroscopic, has water-removing properties (charring of paper, wood, sugar).

The heat of hydration is so great that the mixture may boil, splatter and cause burns. Therefore, it is necessary to add acid to water, and not vice versa, since when water is added to acid, lighter water will be on the surface of the acid, where all the heat released will be concentrated.

Industrial production of sulfuric acid (contact method):

1) 4FeS 2 + 11O 2 → 2Fe 2 O 3 + 8SO 2

2) 2SO 2 + O 2 V 2 O 5 → 2SO 3

3) nSO 3 + H 2 SO 4 → H 2 SO 4 nSO 3 (oleum)

Crushed purified wet pyrite (sulfur pyrite) is poured from above into the kiln for firing in " fluidized bed". From below (counterflow principle) air enriched with oxygen is passed through.
Furnace gas comes out of the furnace, the composition of which is: SO 2, O 2, water vapor (pyrite was wet) and the smallest particles of cinder (iron oxide). The gas is purified from impurities of solid particles (in a cyclone and electrostatic precipitator) and water vapor (in a drying tower).
In the contact apparatus, sulfur dioxide is oxidized using a V 2 O 5 catalyst (vanadium pentoxide) to increase the reaction rate. The process of oxidation of one oxide to another is reversible. Therefore, the optimal conditions for the course of the direct reaction are selected - increased pressure (because the direct reaction proceeds with a decrease in the total volume) and a temperature not higher than 500 C (because the reaction is exothermic).

In the absorption tower, sulfur oxide (VI) is absorbed by concentrated sulfuric acid.
Water absorption is not used, because sulfur oxide dissolves in water with the release of a large amount of heat, so the resulting sulfuric acid boils and turns into steam. In order to avoid the formation of sulfuric acid mist, use 98% concentrated sulfuric acid. Sulfur oxide dissolves very well in such an acid, forming oleum: H 2 SO 4 nSO 3

Chemical properties of sulfuric acid:

H 2 SO 4 is a strong dibasic acid, one of the strongest mineral acids, because of the high polarity, the H - O bond is easily broken.

1) IN aqueous solution sulfuric acid dissociates , forming a hydrogen ion and an acid residue:
H 2 SO 4 \u003d H + + HSO 4 -;
HSO 4 - \u003d H + + SO 4 2-.
Summary Equation:
H 2 SO 4 \u003d 2H + + SO 4 2-.

2) The interaction of sulfuric acid with metals:
Dilute sulfuric acid only dissolves metals in the voltage series to the left of hydrogen:
Zn 0 + H 2 +1 SO 4 (razb) → Zn +2 SO 4 + H 2

3) Sulfuric acid interactionwith basic oxides:
CuO + H 2 SO 4 → CuSO 4 + H 2 O

4) The interaction of sulfuric acid withhydroxides:
H 2 SO 4 + 2NaOH → Na 2 SO 4 + 2H 2 O
H 2 SO 4 + Cu(OH) 2 → CuSO 4 + 2H 2 O

5) Exchange reactions with salts:
BaCl 2 + H 2 SO 4 → BaSO 4 ↓ + 2HCl
The formation of a white precipitate of BaSO 4 (insoluble in acids) is used to detect sulfuric acid and soluble sulfates (qualitative reaction for sulfate ion).

Special properties of concentrated H 2 SO 4:

1) concentrated sulfuric acid is strong oxidizing agent ; when interacting with metals (except Au, Pt) recover to S +4 O 2 , S 0 or H 2 S -2 depending on the activity of the metal. Without heating, it does not react with Fe, Al, Cr - passivation. When interacting with metals with variable valence, the latter are oxidized to higher oxidation states than in the case of a dilute acid solution: Fe0→ Fe 3+ , Cr 0→ Cr 3+ , Mn 0→Mn4+,sn 0→ sn 4+

active metal

8 Al + 15 H 2 SO 4 (conc.) → 4Al 2 (SO 4) 3 + 12H 2 O + 3 H 2 S
4│2Al 0 – 6 e- → 2Al 3+ - oxidation
3│ S 6+ + 8e → S 2– restoration

4Mg+ 5H 2 SO 4 → 4MgSO 4 + H 2 S + 4H 2 O

Medium activity metal

2Cr + 4 H 2 SO 4 (conc.) → Cr 2 (SO 4) 3 + 4 H 2 O + S
1│ 2Cr 0 - 6e → 2Cr 3+ - oxidation
1│ S 6+ + 6e → S 0 - restoration

Metal inactive

2Bi + 6H 2 SO 4 (conc.) → Bi 2 (SO 4) 3 + 6H 2 O + 3 SO2
1│ 2Bi 0 - 6e → 2Bi 3+ - oxidation
3│ S 6+ + 2e →S 4+ - recovery

2Ag + 2H 2 SO 4 → Ag 2 SO 4 + SO 2 + 2H 2 O

2) Concentrated sulfuric acid oxidizes some non-metals, as a rule, to the maximum oxidation state, it itself is reduced toS+4O2:

C + 2H 2 SO 4 (conc) → CO 2 + 2SO 2 + 2H 2 O

S+ 2H 2 SO 4 (conc) → 3SO 2 + 2H 2 O

2P+ 5H 2 SO 4 (conc) → 5SO 2 + 2H 3 PO 4 + 2H 2 O

3) Oxidation of complex substances:
Sulfuric acid oxidizes HI and HBr to free halogens:
2 KBr + 2H 2 SO 4 \u003d K 2 SO 4 + SO 2 + Br 2 + 2H 2 O
2 KI + 2H 2 SO 4 \u003d K 2 SO 4 + SO 2 + I 2 + 2H 2 O
Concentrated sulfuric acid cannot oxidize chloride ions to free chlorine, which makes it possible to obtain HCl by the exchange reaction:
NaCl + H 2 SO 4 (conc.) = NaHSO 4 + HCl

Sulfuric acid removes chemically bound water from organic compounds containing hydroxyl groups. Dehydration of ethyl alcohol in the presence of concentrated sulfuric acid leads to the production of ethylene:
C 2 H 5 OH \u003d C 2 H 4 + H 2 O.

Charring of sugar, cellulose, starch and other carbohydrates upon contact with sulfuric acid is also explained by their dehydration:
C 6 H 12 O 6 + 12H 2 SO 4 \u003d 18H 2 O + 12SO 2 + 6CO 2.

Acid with metal is specific for these classes of compounds. In its course, the hydrogen proton is restored and, in conjunction with the acid anion, is replaced by a metal cation. This is an example of a salt-forming reaction, although there are several types of interactions that do not follow this principle. They proceed as redox and are not accompanied by hydrogen evolution.

Principles of reactions of acids with metals

All reactions with metal lead to the formation of salts. The only exception is, perhaps, the reaction of a noble metal with aqua regia, a mixture of hydrochloric acid, and any other interaction of acids with metals leads to the formation of a salt. If the acid is neither concentrated sulfuric nor nitric, then molecular hydrogen is split off as a product.

But when concentrated sulfuric acid reacts, the interaction with metals proceeds according to the principle of a redox process. Therefore, two types of interactions of typical metals and strong inorganic acids were experimentally distinguished:

• interaction of metals with dilute acids;
• interaction with concentrated acid.

Reactions of the first type proceed with any acid. The only exception is concentrated and nitric acid of any concentration. They react according to the second type and lead to the formation of salts and products of sulfur and nitrogen reduction.

Typical interactions of acids with metals

Metals located to the left of hydrogen in the standard electrochemical series react with other acids of various concentrations, with the exception of nitric acid, to form a salt and release molecular hydrogen. Metals located to the right of hydrogen in the electronegativity series cannot react with the above acids and interact only with nitric acid, regardless of its concentration, with concentrated sulfuric acid and with aqua regia. This is a typical interaction of acids with metals.

Reactions of metals with concentrated sulfuric acid

Reactions with dilute nitric acid

Dilute nitric acid reacts with metals to the left and right of hydrogen. During the reaction with active metals ammonia is formed, which immediately dissolves and reacts with the nitrate anion, forming another salt. With metals of medium activity, the acid reacts with the release of molecular nitrogen. With inactive, the reaction proceeds with the release of dinitric oxide. Most often, several sulfur reduction products are formed in one reaction. Examples of reactions are suggested in the graphical appendix below.

Reactions with concentrated nitric acid

In this case, nitrogen also acts as an oxidizing agent. All reactions end with the formation of salt and isolation. Schemes of the course of redox reactions are proposed in the graphical application. In this case, the reaction with inactive elements deserves special attention. Such interaction of acids with metals is nonspecific.

Reactivity of metals

Metals react with acids quite readily, although there are several inert substances. This and elements having a high standard electrochemical potential. There are a number of metals that are built on the basis this indicator. It's called the electronegativity series. If the metal is in it to the left of hydrogen, then it is able to react with dilute acid.

There is only one exception: iron and aluminum, due to the formation of trivalent oxides on their surface, cannot react with acid without heating. If the mixture is heated, then initially the oxide film of the metal enters into the reaction, and then it dissolves in the acid itself. Metals located to the right of hydrogen in the electrochemical series of activity cannot react with inorganic acid, including with diluted chamois. There are two exceptions to the rule: these metals dissolve in concentrated and dilute nitric acid and aqua regia. Only rhodium, ruthenium, iridium and osmium cannot be dissolved in the latter.

RATIO OF METALS TO ACIDS

Most often in chemical practice such strong acids as sulfuric acid are used. H 2 SO 4, hydrochloric HCl and nitric HNO 3 . Next, consider the ratio of various metals to the listed acids.

hydrochloric acid ( HCl)

Hydrochloric acid is the technical name for hydrochloric acid. It is obtained by dissolving hydrogen chloride gas in water - HCl . Due to its low solubility in water, the concentration of hydrochloric acid under normal conditions does not exceed 38%. Therefore, regardless of the concentration of hydrochloric acid, the process of dissociation of its molecules in an aqueous solution proceeds actively:

HCl H + + Cl -

The hydrogen ions formed in this process H+ act as an oxidizing agent metals in the activity series to the left of hydrogen . The interaction proceeds according to the scheme:

Me + HClsalt +H 2

In this case, the salt is a metal chloride ( NiCl 2 , CaCl 2 , AlCl 3 ), in which the number of chloride ions corresponds to the oxidation state of the metal.

Hydrochloric acid is a weak oxidizing agent, therefore metals with variable valence are oxidized to it to lower positive oxidation states:

Fe0 → Fe2+

Co0 → Co2+

Ni 0 → Ni2+

cr 0 →Cr2+

Mn 0 → Mn2+ And others .

Example:

2 Al + 6 HCl → 2 AlCl 3 + 3 H 2

2│ Al 0 - 3 e- → Al 3+ - oxidation

3│2 H + + 2 e- → H2 - recovery

Hydrochloric acid passivates lead ( Pb ). The passivation of lead is due to the formation on its surface of lead chloride, which is sparingly soluble in water ( II ), which protects the metal from further attack by the acid:

Pb + 2 HCl → PbCl 2 ↓ + H2

Sulfuric acid (H 2 SO 4 )

In industry, very high concentrations of sulfuric acid (up to 98%) are obtained. The difference in the oxidizing properties of a dilute solution and concentrated sulfuric acid with respect to metals should be taken into account.

Dilute sulfuric acid

In a dilute aqueous solution of sulfuric acid, most of its molecules dissociate:

H 2 SO 4 H + + HSO 4 -

HSO 4 - H + + SO 4 2-

Ions formed H+ perform a function oxidizing agent .

Like hydrochloric acid, diluted sulfuric acid solution reacts only with active metals And average activity (located in the activity series up to hydrogen).

The chemical reaction proceeds according to the scheme:

Me+ H2SO4(razb .) → salt+H2

Example :

2 Al + 3 H 2 SO 4 (diff.) → Al 2 (SO 4) 3 + 3 H 2

1│2Al 0 – 6 e- → 2Al 3+ - oxidation

3│2 H + + 2 e- → H2 - recovery

Variable valence metals are oxidized with a dilute solution of sulfuric acid to lower positive oxidation states:

Fe0 → Fe2+

Co0 → Co2+

Ni 0 → Ni2+

cr 0 → Cr2+

Mn 0 → Mn2+ And others .

Lead ( Pb ) does not dissolve in sulfuric acid (if its concentration is below 80%) , since the resulting salt PbSO4 insoluble and creates a protective film on the metal surface.

concentrated sulfuric acid

In a concentrated solution of sulfuric acid (above 68%), most of the molecules are in undissociated condition, therefore sulfur acts as an oxidizing agent , which is in the highest oxidation state ( S+6 ). concentrated H2SO4 oxidizes all metals, the standard electrode potential of which is less than the potential of the oxidizing agent - the sulfate ion SO 4 2- (0.36 V). In this regard, with concentrated react with sulfuric acid and some inactive metals .

The process of interaction of metals with concentrated sulfuric acid in most cases proceeds according to the scheme:

Me + H 2 SO4 (conc.)salt + water + recovery product H 2 SO 4

Recovery Products sulfuric acid can be the following sulfur compounds:

Practice has shown that when a metal interacts with concentrated sulfuric acid, a mixture of reduction products is released, consisting of H 2 S, S and SO 2. However, one of these products is formed in a predominant amount. The nature of the main product is determined metal activity : the higher the activity, the deeper the process of sulfur reduction in sulfuric acid.

The interaction of metals of various activity with concentrated sulfuric acid can be represented by the scheme:

Aluminum (Al ) And iron ( Fe ) do not react with cold concentrated H2SO4 , becoming covered with dense oxide films, however, when heated, the reaction proceeds.

Ag , Au , Ru , Os , Rh , Ir , Pt do not react with sulfuric acid.

concentrated sulfuric acid is strong oxidizing agent , therefore, when metals with variable valence interact with it, the latter are oxidized to higher oxidation states than in the case of a dilute acid solution:

Fe0→ Fe3+,

cr 0→ Cr3+,

Mn 0→Mn4+,

sn 0→ sn 4+

Lead ( Pb ) oxidized to divalent state with the formation of soluble lead hydrosulfatePb ( HSO 4 ) 2 .

Examples:

Active metal

8 A1 + 15 H 2 SO 4(conc.) →4A1 2 (SO 4) 3 + 12H 2 O + 3H 2 S

4│2 Al 0 – 6 e- → 2 Al 3+ - oxidation

3│ S 6+ + 8 e → S 2- - recovery

Medium activity metal

2 Cr + 4 H 2 SO 4 (conc.) → Cr 2 (SO 4) 3 + 4 H 2 O + S

1│ 2Cr 0 - 6e → 2Cr 3+ - oxidation

1│ S 6+ + 6 e → S 0 - recovery

Metal inactive

2Bi + 6H 2 SO 4(conc.) → Bi 2 (SO 4) 3 + 6H 2 O + 3SO 2

1│ 2Bi 0 – 6e → 2Bi 3+ – oxidation

3│ S 6+ + 2 e → S 4+ - recovery

Nitric acid ( HNO 3 )

A feature of nitric acid is that nitrogen, which is part of NO 3 - has a highest oxidation state of +5 and therefore has strong oxidizing properties. The maximum value of the electrode potential for the nitrate ion is 0.96 V, therefore nitric acid is a stronger oxidizing agent than sulfuric acid. The role of an oxidizing agent in the reactions of interaction of metals with nitric acid is played by N 5+ . Hence, hydrogen H 2 never stands out in the interaction of metals with nitric acid ( regardless of concentration ). The process proceeds according to the scheme:

Me + HNO 3 salt + water + recovery product HNO 3

Recovery Products HNO 3 :

Usually, the reaction of nitric acid with a metal produces a mixture of reduction products, but as a rule, one of them is predominant. Which of the products will be the main one depends on the concentration of the acid and the activity of the metal.

Concentrated nitric acid

A concentrated acid solution is considered to have a densityρ > 1.25 kg / m 3, which corresponds to
concentrations > 40%. Regardless of the activity of the metal, the reaction of interaction with HNO 3 (conc.) proceeds according to the scheme:

Me + HNO 3 (conc.)→ salt + water + NO 2

Noble metals do not interact with concentrated nitric acid (Au , Ru , Os , Rh , Ir , Pt ), and a number of metals (Al , Ti , Cr , Fe , co , Ni ) at low temperature passivated with concentrated nitric acid. The reaction is possible with an increase in temperature, it proceeds according to the scheme presented above.

Examples

active metal

Al + 6 HNO 3( conc .) → Al (NO 3 ) 3 + 3 H 2 O + 3 NO 2

1│ Al 0 - 3 e → Al 3+ - oxidation

3│ N 5+ + e → N 4+ - recovery

Medium activity metal

Fe + 6 HNO 3 (conc.) → Fe (NO 3) 3 + 3H 2 O + 3NO

1│ Fe 0 - 3e → Fe 3+ - oxidation

3│ N 5+ + e → N 4+ - recovery

Metal inactive

Ag + 2HNO 3(conc.) → AgNO 3 + H 2 O + NO 2

1│ Ag 0 - e → Ag + - oxidation

1│ N 5+ + e → N 4+ - recovery

Dilute nitric acid

Recovery product nitric acid in a dilute solution depends on metal activity participating in the reaction:

Examples:

active metal

8 Al + 30 HNO 3 (diff.) → 8Al(NO 3) 3 + 9H 2 O + 3NH 4 NO 3

8│ Al 0 - 3e → Al 3+ - oxidation

3│ N 5+ + 8 e → N 3- - recovery

The ammonia released during the reduction of nitric acid immediately interacts with an excess of nitric acid, forming a salt - ammonium nitrate NH4NO3:

NH 3 + HNO 3 → NH 4 NO 3.

Medium activity metal

10Cr + 36HNO 3( dec.) → 10Cr(NO 3) 3 + 18H 2 O + 3N 2

10│ Cr 0 - 3 e → Cr 3+ - oxidation

3│ 2 N 5+ + 10 e → N 2 0 - recovery

Except molecular nitrogen ( N 2 ) when metals of medium activity interact with dilute nitric acid, it is formed in equal number Nitric oxide ( I) - N 2 O . In the reaction equation, you need to write one of these substances .

Metal inactive

3Ag + 4HNO 3(deb.) → 3AgNO 3 + 2H 2 O + NO

3│ Ag 0 - e → Ag + - oxidation

1│ N 5+ + 3 e → N 2+ - recovery

"Aqua regia"

"Aqua regia" (formerly called vodka acids) is a mixture of one volume of nitric acid and three to four volumes of concentrated hydrochloric acid, which has a very high oxidative activity. Such a mixture is capable of dissolving some low-active metals that do not interact with nitric acid. Among them is the "king of metals" - gold. This effect of "aqua regia" is explained by the fact that nitric acid oxidizes hydrochloric acid with the release of free chlorine and the formation of nitrogen chlorine oxide ( III ), or nitrosyl chloride - NOCl :

HNO 3 + 3 HCl → Cl 2 + 2 H 2 O + NOCl

2 NOCl → 2 NO + Cl 2

Chlorine at the moment of release consists of atoms. Atomic chlorine is the strongest oxidizing agent, which allows "royal vodka" to act on even the most inert "noble metals".

The oxidation reactions of gold and platinum proceed according to the following equations:

Au + HNO 3 + 4 HCl → H + NO + 2H 2 O

3Pt + 4HNO 3 + 18HCl → 3H 2 + 4NO + 8H 2 O

On Ru, Os, Rh and Ir "royal vodka" does not work.

E.A. Nudnova, M.V. Andriukhova

Sulfur trioxide is usually a colorless liquid. It can also exist as ice, fibrous crystals, or gas. When sulfur trioxide is exposed to air, white smoke begins to be released. It is a constituent element of such a chemical active substance like concentrated sulfuric acid. It is a clear, colorless, oily and highly corrosive liquid. It is used in the manufacture of fertilizers, explosives, other acids, the oil industry, and lead-acid batteries in automobiles.

Concentrated sulfuric acid: properties

Sulfuric acid dissolves well in water, is corrosive to metals and fabrics, and chars wood and most other materials upon contact. organic matter. Long-term exposure to low concentrations or short-term exposure to high concentrations may result in adverse health effects from inhalation.

Concentrated sulfuric acid is used to make fertilizers and other chemicals, in oil refining, in iron and steel making, and for many other purposes. Because it has a high enough boiling point, it can be used to release more volatile acids from their salts. Concentrated sulfuric acid has a strong hygroscopic property. It is sometimes used as a drying agent to dehydrate (remove water by chemical means) many compounds, such as carbohydrates.

Sulfuric acid reactions

Concentrated sulfuric acid reacts in an unusual way to sugar, leaving behind a brittle spongy black mass of carbon. A similar reaction is observed when exposed to skin, cellulose and other plant and animal fibers. When concentrated acid is mixed with water, a large number of enough heat to bring it to a boil. For dilution, it should be added slowly to cold water with constant stirring to limit heat buildup. Sulfuric acid reacts with liquid, forming hydrates with pronounced properties.

physical characteristics

A colorless and odorless liquid in a dilute solution has a sour taste. Sulfuric acid is extremely aggressive when exposed to the skin and all tissues of the body, causing severe burns on direct contact. In its pure form, H 2 SO4 is not a conductor of electricity, but the situation changes in opposite side with the addition of water.

Some properties is that the molecular weight is 98.08. The boiling point is 327 degrees Celsius, the melting point is -2 degrees Celsius. Sulfuric acid is a strong mineral acid and one of the main products of the chemical industry due to its wide commercial use. It is formed naturally from the oxidation of sulfide materials such as iron sulfide.

The chemical properties of sulfuric acid (H 2 SO4) are manifested in various chemical reactions:

1. When interacting with alkalis, two series of salts are formed, including sulfates.
2. Reacts with carbonates and bicarbonates to form salts and carbon dioxide (CO 2).
3. It affects metals differently, depending on the temperature and degree of dilution. Cold and dilute yields hydrogen, hot and concentrated yields SO 2 emissions.
4. When boiling, a solution of H 2 SO4 (concentrated sulfuric acid) decomposes into sulfur trioxide (SO 3) and water (H 2 O). The chemical properties also include the role of a strong oxidizing agent.

fire hazard

Sulfuric acid is highly reactive to ignite fine combustible materials on contact. When heated, highly toxic gases begin to be released. It is explosive and incompatible with a huge number of substances. At elevated temperatures and pressures, rather aggressive chemical changes and deformation. May react violently with water and other liquids, causing splashing.

health hazard

Sulfuric acid corrodes all tissues of the body. Inhalation of vapors can cause serious lung damage. Damage to the mucous membrane of the eyes can lead to complete loss of vision. Skin contact may cause severe necrosis. Even a few drops can be fatal if the acid gains access to the windpipe. Chronic exposure can cause tracheobronchitis, stomatitis, conjunctivitis, gastritis. Gastric perforations and peritonitis may occur, accompanied by circulatory collapse. Sulfuric acid is a highly caustic substance that must be handled with extreme care. Signs and symptoms upon exposure can be severe and include drooling, intense thirst, difficulty swallowing, pain, shock, and burns. The vomit is usually the color of ground coffee. Acute inhalation exposure may result in sneezing, hoarseness, choking, laryngitis, dyspnea, irritation respiratory tract and chest pain. Bleeding from the nose and gums, pulmonary edema, chronic bronchitis, and pneumonia may also occur. Exposure to the skin can result in severe painful burns and dermatitis.

First aid

1. Move victims to fresh air. Emergency personnel should avoid exposure to sulfuric acid while doing so.
2. Assess vital signs, including pulse and respiratory rate. If a pulse is not detected, perform resuscitation, depending on the additional injuries received. If breathing is present and difficult, provide respiratory support.
3. Remove soiled clothing as soon as possible.
4. In case of contact with eyes, rinse warm water at least 15 minutes, on the skin - wash with soap and water.
5. When inhaling toxic fumes, rinse your mouth big amount water, drink and independently induce vomiting is prohibited.
6. Deliver the injured to a medical facility.