Chemistry - comprehensive preparation for external independent assessment. Chloric acid

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Structural formula

True, empirical, or gross formula: C4H4O

The chemical composition of perchloric acid

Molecular weight: 100.457

Perchloric acid HClO 4- monobasic acid, one of the strongest (in aqueous solution, pK = ~ -10), anhydrous - exceptionally strong oxidizing agent, as it contains chlorine in the highest oxidation state +7.

Properties

Physical Properties

Colorless volatile liquid, highly fuming in air, monomeric in vapor. Anhydrous perchloric acid is highly reactive and unstable. Liquid HClO 4 is partially dimerized, it is characterized by equilibrium autodehydration: 3HClO 4 ↔ H 3 O + + ClO 4 - + Cl 2 O 7

Chemical properties

Explosive. Perchloric acid and its salts (perchlorates) are used as oxidizing agents. Perchloric acid, as one of the strongest, dissolves gold and platinum metals, and in reaction with silver forms chloric acid:
3HClO 4 + 2Ag \u003d 2AgClO 4 + HClO 3 + H 2 O
Non-metals and active metals reduce perchloric acid to hydrogen chloride
8As + 5HClO 4 + 12H 2 O = 8H 3 AsO 4 + 5HCl (this reaction is used in metallurgy to purify ores)
Iodine perchlorate is obtained in the laboratory by treating a solution of iodine in anhydrous perchloric acid with ozone:
I 2 + 6HClO 4 + O 3 \u003d 2I (ClO 4) 3 + 3H 2 O
Being extremely strong unstable, perchloric acid decomposes:
4HClO 4 \u003d 4ClO 2 + 3O 2 + 2H 2 O
Perchloric acid is highly soluble in fluoro- and chlorine-organic solvents such as CF 3 COOH, CHCl 3 , CH 2 Cl 2 and others. Mixing with solvents that exhibit reducing properties can lead to ignition and explosion. Perchloric acid is miscible with water in any ratio and forms a series of hydrates HClO 4 ×nH 2 O (where n = 0.25…4). HClO 4 H 2 O monohydrate has a melting point of +50 o C. Concentrated solutions of perchloric acid, unlike anhydrous acid, have an oily consistency. Aqueous solutions of perchloric acid are stable and have low oxidizing power. Perchloric acid forms an azeotrope with water, boiling at 203°C and containing 72% perchloric acid. Solutions of perchloric acid in chlorine-containing hydrocarbons are superacids (superacids). Perchloric acid is one of the strongest inorganic acids, in its environment even acidic compounds behave like bases, adding a proton and forming acyl perchlorate cations: P (OH) 4 + ClO 4 - , NO 2 + ClO 4 - .
With slight heating under reduced pressure of a mixture of perchloric acid with phosphoric anhydride, a colorless oily liquid is distilled off - perchloric anhydride:
2HClO 4 + P 4 O 10 → Cl 2 O 7 + H 2 P 4 O 11
perchloric acid are called perchlorates.

Receipt

Aqueous solutions of perchloric acid are obtained by electrochemical oxidation of hydrochloric acid or chlorine dissolved in concentrated perchloric acid, as well as by the exchange decomposition of sodium or potassium perchlorates with strong inorganic acids.
Anhydrous perchloric acid is formed by the interaction of sodium or potassium perchlorates with concentrated sulfuric acid, as well as aqueous solutions of perchloric acid with oleum: KClO 4 + H 2 SO 4 → KHSO 4 + HClO 4

Application

Concentrated aqueous solutions of perchloric acid are widely used in analytical chemistry and also for the preparation of perchlorates.
Perchloric acid is used in the decomposition of complex ores, in the analysis of minerals, and also as a catalyst.
Salts of perchloric acid: potassium perchlorate is sparingly soluble in water, used in the manufacture of explosives, magnesium perchlorate (anhydrone) is a desiccant.

Anhydrous perchloric acid cannot be stored and transported for a long time, since when stored in normal conditions it decomposes slowly, is colored by chlorine oxides formed during its decomposition, and may spontaneously explode. But its aqueous solutions are quite stable.

Perchloric acid (formula HClO4) is a monobasic anhydrous acid. It contains chlorine (Cl) in the highest degree of oxidation, for this reason it is the strongest oxidizing agent. Explosive.

Properties of perchloric acid

1. It is a volatile liquid without color, it smokes strongly in the air, it is monomeric in vapors. Unstable and very reactive. This acid is characterized by autodehydration:

3HClO4 = H3O+ (cation) + ClO- (anion) + Cl2O7 (chlorine oxide)

2. This substance is highly soluble in chlorine and fluorine organic solvents such as CH2Cl2 (methylene chloride), CHCl3 (chloroform) and others. It is miscible with other solvents, exhibits reducing properties, and if handled carelessly, it can lead to an explosion or fire.

3. Mixes well with water (H2O) in any ratio. Forms several hydrates. Concentrated solutions of this acid have a slightly oily consistency. Aqueous solutions of this acid have good stability and low oxidizing power. With water, the substance we are considering forms an azeotropic mixture, which boils at a temperature of 203 degrees and contains 72 percent HClO4.

4. Perchloric acid (formula HClO4) is one of the following. Because of this, in its environment, some acidic compounds behave like bases.

5. Under conditions of reduced pressure, with weak heating of a mixture of perchloric acid with phosphoric anhydride, an oily colorless liquid is formed - perchloric anhydride:

2HClO4 (perchloric acid) + P4O10 (phosphoric anhydride) = Cl2O7 (perchloric anhydride) + H2P4O11

How to get

1. Aqueous solutions of a given substance can be obtained in two ways. The first is the electrochemical oxidation of chlorine or hydrochloric acid in concentrated hydrochloric acid, and the second is the exchange decomposition of sodium or potassium perchlorates with inorganic strong acids.

2. Anhydrous perchloric acid can also be obtained in two ways. The first is the interaction of potassium (K) or sodium (Na) perchlorates with concentrated sulfuric acid, and the second is the interaction of oleum with an aqueous solution of perchloric acid:

KClO4 (aqueous perchloric acid) + H2SO4 = KHSO4 (potassium hydrogen sulfate) + HClO4 (perchloric acid)

The use of perchloric acid

Concentrated solutions are widely used to obtain perchlorates (salts of a given acid) and in analytical chemistry;

Perchloric acid is used in the decomposition of ores, as a catalyst, and in the analysis of minerals;

Potassium perchlorate (formula: KClO4), a salt of this acid, is used in making magnesium perchlorate (anhydrone, Mg(ClO4)2) as a desiccant.

Safety at work

Perchloric anhydrous acid cannot be stored and transported for a long time, since under standard conditions it quickly decomposes and can subsequently spontaneously explode.

Other inorganic chlorine acids:

1. (formula: HCl) - monobasic caustic, fuming liquid in air. It is used in electroplating (pickling, etching) and in hydrometallurgy, for cleaning metals during tinning and soldering, for obtaining chlorides of manganese, zinc, iron and other metals. V Food Industry given substance registered as food additive E507.

2. Hypochlorous acid (formula: HClO) is a monobasic, very weak acid. It can only exist in solutions. It is used for sanitary purposes, as well as for bleaching fabrics and pulp.

3. Chlorous acid(HClO2) - monobasic acid medium strength. Unstable in free form, in a dilute aqueous solution it usually decomposes rapidly. The anhydride of this acid is still unknown.

4. Perchloric acid (HClO3) is a monobasic strong acid. Not obtained in free form, as it decomposes in aqueous solutions exists at a concentration below 30 percent. Fairly stable at low temperatures.

SECTION II. INORGANIC CHEMISTRY

9. Non-metallic elements and their compounds. non-metals

9.2. Halogens

9.2.2. Hydrogen chloride. Chloric acid

Hydrogen chloride (chlorine water)

The hydrogen chloride molecule is covalent, linear, polar, with one a -communication. An atom of electronegative Chlorine shifts in its direction a joint electron cloud:

Crystal lattices of solid hydrogen chloride molecular. The oxidation state of Chlorine is the lowest (-1).

Physical properties of hydrogen chloride

NS l - a colorless gas with an unpleasant pungent odor, heavier than air, soluble in water. Smokes in the air, because with water vapor, which is in humid air acid droplets are formed. Up to 500 volumes of HC dissolve in one volume of water l , in this case, hydrochloric acid is formed with a maximum mass fraction of hydrogen chloride 38- 40%. Chloride day is pretty toxic substance irritates the respiratory tract.

Extraction of hydrogen chloride

In the laboratory, chlorine water is produced by the action of concentrated sulfuric acid on solid sodium chloride (when heated):

If you use an excess of sulfuric acid, then an acid salt is formed - sodium hydrogen sulfate:

In industry, chlorine water is obtained by burning hydrogen in an atmosphere of chlorine:

Chloric acid

Water solution hydrogen chloride is called perchloric acid. In the human body, perchloric acid is secreted by the cells of the gastric mucosa and promotes the digestion of proteins by pepsin (creates an acidic environment necessary for the functioning of the enzyme).

It is a colorless, volatile liquid. Concentrated perchloric acid "smokes" in air, because hydrogen chloride molecules are released from the solution. Chloric acid is a strong, monobasic acid. The degree of its dissociation in dilute solutions exceeds 90%:

Chemical properties

1. Chloric acid exhibits general properties acids: reacts with metals that are placed in the vitiscuval row to hydrogen, interacts with basic and amphoteric oxides, with bases and amphoteric hydroxides, with salts:

When an acid interacts with rich acid bases, the formation of basic salts is possible:

A white curd precipitate AgCl. This is a qualitative reaction to chloride ion C l- . Argentum chloride, unlike other insoluble salts AgBr, Agl (respectively yellow and yellow), dissolves in excess NH3:

Chlorous acid

Chem. formula HClO 2 Physical Properties State colorless solution Molar mass 68.46 g/mol Chemical properties pK a 1.96 Classification Reg. CAS number 13898-47-0 Data is based on standard conditions (25 °C, 100 kPa) unless otherwise noted.

Chlorous acid- HClO 2 , monobasic acid of medium strength. The corresponding salts are chlorites.

Properties

Chloric acid HClO 2 in its free form is unstable, even in a dilute aqueous solution it quickly decomposes:

$\mathsf(4HClO_2 \rightarrow HCl + HClO_3 + 2ClO_2 + H_2O)$ $\mathsf(Ba(ClO_2)_2 + H_2SO_4 \rightarrow BaSO_4\downarrow + 2HClO_2)$

And also by reaction:

$\mathsf(2ClO_2 + H_2O_2 + 2NaOH\rightarrow 2NaClO_2 + O_2 + 2H_2O)$

Salts of hydrochloric acid are called chlorites, they are usually colorless and highly soluble in water. Unlike hypochlorites, chlorites exhibit pronounced oxidizing properties only in an acidic environment. Of the salts, sodium chlorite NaClO 2, used for bleaching fabrics and paper pulp, has the greatest use. Sodium chlorite is obtained by the reaction:

$\mathsf(2ClO_2 + PbO + 2NaOH \rightarrow PbO_2\downarrow + 2NaClO_2 + H_2O)$

Anhydrous NaClO 2 explodes on impact and heating; ignites on contact with organic matter, rubber, paper, etc.

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Literature

Akhmetov N. S. "General and inorganic chemistry» M.: Higher school, 2001
Karapetyants M. Kh., Drakin S. I. "General and inorganic chemistry" M .: Chemistry 1994

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An excerpt characterizing perchloric acid

- How? You, with all your weight, attacked the unfortunate Mortier with one division, and this Mortier is slipping between your hands? Where is the victory?
“However, speaking seriously,” answered Prince Andrei, “we can still say without boasting that this is a little better than Ulm ...
“Why didn’t you take us one, at least one marshal?”
- Because not everything is done as expected, and not as regularly as in the parade. We thought, as I told you, to go to the rear by seven o'clock in the morning, and did not arrive even at five in the evening.
"Why didn't you come at seven o'clock in the morning?" You should have come at seven o'clock in the morning, - Bilibin said smiling, - you should have come at seven o'clock in the morning.
“Why didn’t you convince Bonaparte by diplomatic means that it was better for him to leave Genoa? - Prince Andrei said in the same tone.
“I know,” Bilibin interrupted, “you think it’s very easy to take marshals while sitting on the sofa in front of the fireplace.” It's true, but still, why didn't you take it? And do not be surprised that not only the Minister of War, but also the august emperor and King Franz will not be very happy with your victory; and I, the unfortunate secretary of the Russian embassy, do not feel any need to give my Franz a taler as a token of joy and let him go with his Liebchen [darling] to the Prater ... True, there is no Prater here.
He looked directly at Prince Andrei and suddenly pulled the collected skin off his forehead.
“Now it’s my turn to ask you why, my dear,” said Bolkonsky. - I confess that I don’t understand, maybe there are diplomatic subtleties beyond my weak mind, but I don’t understand: Mack loses an entire army, Archduke Ferdinand and Archduke Karl do not give any signs of life and make mistakes after mistakes, finally, one Kutuzov wins a real victory, destroys the charme [charm] of the French, and the Minister of War is not even interested in knowing the details.
“It is from this, my dear. Voyez vous, mon cher: [You see, my dear:] hooray! for the tsar, for Russia, for the faith! Tout ca est bel et bon, [all this is fine and good,] but what do we, I say, the Austrian court, care about your victories? Bring us your good news about the victory of Archduke Charles or Ferdinand - un archiduc vaut l "autre, [one archduke is worth another,] as you know - at least over a company of Bonaparte's fire brigade, this is another matter, we will thunder into cannons. Otherwise this , as if on purpose, can only tease us. Archduke Karl does nothing, Archduke Ferdinand is covered with disgrace. You leave Vienna, you no longer defend, comme si vous nous disiez: [as if you told us:] God is with us, and God is with you, with your capital. One general whom we all loved, Schmitt: you bring him under a bullet and congratulate us on the victory! ... You must admit that it is impossible to imagine more irritating than the news that you bring. C "est comme un fait expres, comme unfait expres. [This is as if on purpose, as if on purpose.] Besides, well, if you won a brilliant victory, even if Archduke Karl won, what would change the general course of affairs? It's too late now that Vienna is occupied by French troops.

With the release of hydrogen, interacts with metal oxides and.

Concentrated hydrochloric acid contains 37% HCl and has a density of 1.19 g/cm3. It has a pungent odor and "smokes" in air due to the evolution of hydrogen chloride gas. Technical acid has yellow, which is due to the admixture mainly of iron salts.

1. History of discovery

It is difficult to say who and when first received hydrochloric acid. It is known that already at the end of the XV century. alchemist Vasily Valentin and in the 16th century. Andreas Libavius, in his executive search for a miraculous life elixir, calcined table salt with galloon and vitriol in his alchemical devices and obtained a product that was described under the name "sour alcohol". This is what hydrochloric acid was now familiar to us, very impure.

For the first researchers, this was a completely new substance, which had properties that greatly amazed their imagination. Sniffing it, they choked and coughed, "sour alcohol" of smoke in the air. When tasted, it burned the tongue and palate, it corroded metals, and destroyed tissues.

In 1658, the German chemist I.R. Glauber (1604-1670) found new way obtaining hydrochloric acid, which he called "hydrochloric alcohol". This method is still widely used in laboratories. He warmed up table salt with concentrated sulfuric acid and the "smoke" that was released was absorbed by water.

In 1772, the English chemist Joseph Priestley (1733-1804) found that the action of sulfuric acid on sodium chloride releases a colorless gas that can be collected over mercury, and this gas has an extremely high ability to dissolve in water. An aqueous solution of this gas was called "hydrochloric acid" (acidum muriaticum), and the gas itself was called "pure gaseous hydrochloric acid" by Priestley.

In 1774, the Swedish chemist K.V. Scheele (1742-1786), investigating the effect of hydrochloric acid (which he also called "hydrochloric alcohol") on manganese (IV) oxide, found that it dissolves in hydrochloric acid in the cold, forming a dark brown solution, from which, when heated, a yellow-green gas is released, which has a very pungent odor, the ability to destroy vegetable dyes and acts on all metals, not excluding gold. Scheele, as a follower of the phlogiston theory that prevailed at that time, believed that the meaning of this reaction is that under the action of manganese (IV) oxide with hydrochloric acid, phlogiston leaves it, due to which hydrochloric acid turns into a yellow-green gas. Therefore, he called the gas itself "dephlogisticated with hydrochloric acid."