hydrogen iodide

Hydrogen iodide
Are common
Systematic name	Hydrogen iodine
Chemical formula	HI
Rel. molek. weight	127.904 a. eat.
Molar mass	127.904 g/mol
Physical properties
Matter density	2.85 g/ml (-47 °C) g/cm³
Condition (st. conv.)	colorless gas
Thermal properties
Melting temperature	-50.80 °C
Boiling temperature	-35.36 °C
Decomposition temperature	300°C
Critical point	150.7°C
Enthalpy (st. arb.)	26.6 kJ/mol
Chemical properties
pK a	- 10
Solubility in water	72.47 (20°C) g/100 ml
Classification
CAS number

Hydrogen iodine HI is a colorless suffocating gas that smokes strongly in air. Unstable, decomposes at 300 °C.

Hydrogen iodide is highly soluble in water. It forms an azeotrope boiling at 127°C with an HI concentration of 57%.

Receipt

In industry, HI is obtained by the reaction of I 2 with hydrazine, which also results in N 2:

2 I 2 + N 2 H 4 → 4 HI + N 2

In the laboratory, HI can also be obtained using the following redox reactions:

H 2 S + I 2 → S↓ + 2HI

Or by hydrolysis of phosphorus iodide:

PI 3 + 3H 2 O → H 3 PO 3 + 3HI

Hydrogen iodine is also obtained by the interaction of simple substances H 2 and I 2. This reaction occurs only when heated and does not proceed to the end, since equilibrium is established in the system:

H 2 + I 2 → 2HI

Properties

An aqueous solution of HI is called hydroiodic acid(colorless liquid with a pungent odor). Hydroiodic acid is the strongest acid. Salts of hydroiodic acid are called iodides.

Hydrogen iodide is a strong reducing agent. When standing, an aqueous solution of HI turns brown due to its gradual oxidation with atmospheric oxygen and the release of molecular iodine:

4HI + O 2 → 2H 2 O + 2I 2

HI is able to reduce concentrated sulfuric acid to hydrogen sulfide:

8HI + H 2 SO 4 → 4I 2 + H 2 S + 4H 2 O

Like other hydrogen halides, HI adds to multiple bonds (electrophilic addition reaction):

HI + H 2 C \u003d CH 2 → H 3 CCH 2 I

Application

Hydrogen iodine is used in laboratories as a reducing agent in many organic syntheses, as well as for the preparation of various iodine-containing compounds.

Literature

• Akhmetov N.S. "General and inorganic chemistry" M.: Higher school, 2001

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See what "Hydrogen iodide" is in other dictionaries:

See Yod...

C2H5I E. iodide, liquid, boiling point 72.34°; D14.5 = 1.9444. Freshly prepared E. iodide is colorless, turns brown on standing and decomposes with the release of free iodine. It has a strong ethereal scent. It lights up hard. Ignited, ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

- (chemical) one of the elements of the halogen group, chemical sign J, atomic weight 127, according to Stas 126.85 (O = 16), Courtois discovered in 1811 in the mother brine of seaweed ash. Its nature, as an element, was established by Gay Lussac and is closer to him ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

- (also methyl hydrogen, formene) saturated hydrocarbon of composition CH4, the first member of the CnH2n + n series, one of the simplest carbon compounds around which all the others are grouped and from which can be produced through the substitution of atoms ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

The alchemists accepted that metals are complex bodies, consisting of spirit, soul and body, or mercury, sulfur and salt; by spirit, or mercury, they understood not ordinary mercury, but volatility and metallic properties, for example, brilliance, malleability; under the gray (soul) ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

The phenomena of chemical equilibrium cover the area of ​​incomplete transformations, i.e., such cases when the chemical transformation of a material system is not completed to the end, but stops after a part of the substance undergoes a change. IN… … Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

- (chem.; Phosphore French, Phosphor German, Phosphorus English and Latin, from where the designation P, sometimes Ph; atomic weight 31 [In recent times, the atomic weight of F. found (van der Plaats) is: 30.93 by restoration of a certain weight F. metal ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

- (chem.). This is the name of four elementary bodies that are in the seventh group of the periodic system of elements: fluorine F \u003d 19, chlorine Cl \u003d 3.5, bromine Br \u003d 80 and iodine J \u003d 127. The last three are very similar to each other, and fluorine stands somewhat apart. … … Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Or halogens (chem.) So, four elementary bodies that are in the seventh group of the periodic system of elements are called: fluorine F \u003d 19, chlorine Cl \u003d 3.5, bromine Br \u003d 80 and iodine J \u003d 127. The last three are very similar to each other , and fluorine costs a few ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Hydrocarbon of the limiting series C2H4; found in nature, in excretions from the soil of oil-bearing areas. Artificially obtained for the first time by Kolbe and Frankland in 1848 under the action of metallic potassium on propionitrile, by them in the next 1849 ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

It is colorless and mixes easily with water. One hundred milliliters of liquid contains 132 grams of hydrogen iodine. This is at normal pressure and room temperature. When heated to 100 degrees, already 177 grams dissolve in water. Let's find out what the resulting solution is capable of.

Properties of hydroiodic acid

Being strong, the connection manifests itself as a typical. This is expressed, for example, in reactions with . Interaction takes place with those of them that are to the left. It is in the place of this element that the atom rises.

It turns out iodite. Hydrogen is escaping. With salts hydroiodic acid reacts also in the case of gas evolution. More rarely, the interaction results in the precipitation of one of its products.

The heroine of the article also reacts with basic oxides, like other strong ones. Basic oxides are compounds with oxygen of metals with the first or second oxidation states. The interaction leads to the release of water and the production of iodite, that is, hydroiodic acid salts.

The reaction of the heroine with the bases also gives water and. Interaction typical of the strong. However, most substances are tribasic. This indicates the content of 3 hydrogen atoms in the molecule.

In a hydrogen iodide compound, there is only one gas atom, which means that the substance is monobasic. In addition, it refers to oxygen-free. As hydrochloric is written HCl, so formula of hydroiodic acid- H.I. Basically, it's a gas. What about the aqueous solution? It is considered true, but rarely found in laboratories. The problem is the storage of the solution.

Strong restorative properties of hydroiodic acid lead to rapid oxidation. As a result, pure water and a brown precipitate remain at the bottom of the tube. This is iodine diiodate. That is, in solution, the heroine is short-lived.

The process of "corruption" is inevitable. But, there is a way to restore the heroine of the article. Do it with . distilled in his presence. We need an inert atmosphere, for example, from argon, or carbon dioxide.

An alternative to phosphorus is hydrogen dihydrogen phosphate with the formula H (PH 2 O 2). The presence of hydrogen sulfide during the distillation of hydrogen iodine also has a positive effect. Therefore, do not throw out the stratified mixture and mix fresh reagents. can be restored.

Until the iodine in the solution is oxidized, the liquid is colorless and smells strongly. The solution is azeototropic. This means that when boiling, the composition of the mixture remains the same. Evaporation and liquid phases are in equilibrium. Hydroiodine boils, by the way, not at 100, but at 127 degrees Celsius. If heated to 300, the substance will decompose.

Now, let's find out why in the series of strong hydrogen iodine is considered the strongest. Enough example of interaction with "colleagues". So, "meeting" with a sulfuric concentrate, hydrogen iodine reduces it to hydrogen sulfide. If the sulfur compound meets with others, it will act as a reducing agent.

The ability to donate hydrogen atoms is the main property. These atoms are attached to other elements, new molecules are formed. Here is the recovery process. Restoration reactions also underlie the receipt of the heroine of the article.

Obtaining hydroiodic acid

Due to the instability, the hydriodine compound actively smokes. Given the causticity of vapors, they work with the heroine of the article only in laboratory conditions. Usually, they take hydrogen sulfide and iodine. The following reaction is obtained: H 2 S + I 2 à S + 2HI. Elementary, formed as a result of interaction, precipitates.

You can also get a reagent by combining a suspension of iodine, water and sulfur oxide. The result will be sulfuric acid and the heroine of the article. The reaction equation looks like this: I 2 + SO 2 + 2H 2 O à 2HI + H 2 SO 4.

The third way to obtain hydrogen iodine is the combination of potassium iodite and. At the output, in addition to the heroine of the article, potassium hydrogen orthophosphate will be obtained. Hydrogen iodine is released as a gas in all reactions. Trapped with water, getting a solution. The tube through which the gas flows must not be lowered into the liquid.

At large enterprises, hydrogen iodine is produced by the reaction of iodine with hydrazine. The latter, like the heroine of the article, is colorless and smells strongly. The chemical record of the interaction looks like this: - 2I 2 + N 2 H 4 à4HI + N 2 . As you can see, the reaction gives a greater "exhaust" of hydrogen iodine than laboratory methods.

There remains an obvious, but unfavorable option - the interaction of pure elements. The complexity of the reaction is that it proceeds only when heated. In addition, equilibrium is quickly established in the system.

This prevents the reaction from reaching its end. Equilibrium in chemistry is called the point when the system begins to resist the impact on it. So combining elemental iodine and hydrogen is just a chapter in chemistry textbooks, not a practical method.

The use of hydriodic acid

Like others, hydroiodic acid - electrolyte. The heroine of the article is capable of disintegrating into ions, through which the current “runs”. For this run, you need to place the cathode and anode in the solution. One is positively charged, the other negatively.

The resulting resources serve in capacitors. Electrolytes are used as current sources and as a medium for gilding, silvering metals and applying other coatings to them.
Industrialists also use the reducing properties of hydrogen iodine. Strong buy for organic syntheses. Thus, alcohols are reduced by hydrogen iodine to alkanes. They include all . Before alkanes, the heroine of the article restores, in the same way, halides and others.

Only some chlorine derivatives cannot be reduced with hydrogen iodine. Considering this, few people are sad. If in the laboratory hydroiodic acid was neutralized means the company is well funded. Let's get acquainted with the price tags for the reagent.

The price of hydriodic acid

For laboratories, hydrogen iodine is sold in liters. Store the reagent in the dark. In the light, the liquid quickly turns brown, decomposes into water and diode iodate. The container is tightly closed. The heroine of the article does not corrode plastic. This is where the reagent is stored.

Demand is 57 percent. It rarely happens in warehouses, it is manufactured mainly under. The price tag is usually set in euros. In translation, it turns out at least 60,000. In euros, this is for 1,000. Therefore, they purchase a reagent as needed. If there is an alternative, take it. Hydroiodine is not only the strongest, but also the most expensive.

acids complex substances are called, the composition of the molecules of which includes hydrogen atoms that can be replaced or exchanged for metal atoms and an acid residue.

According to the presence or absence of oxygen in the molecule, acids are divided into oxygen-containing(H 2 SO 4 sulfuric acid, H 2 SO 3 sulfurous acid, HNO 3 nitric acid, H 3 PO 4 phosphoric acid, H 2 CO 3 carbonic acid, H 2 SiO 3 silicic acid) and anoxic(HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H 2 S hydrosulfide acid).

Depending on the number of hydrogen atoms in an acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms). For example, nitric acid HNO 3 is monobasic, since there is one hydrogen atom in its molecule, sulfuric acid H 2 SO 4 – dibasic, etc.

There are very few inorganic compounds containing four hydrogen atoms that can be replaced by a metal.

The part of an acid molecule without hydrogen is called an acid residue.

Acid Residue they can consist of one atom (-Cl, -Br, -I) - these are simple acid residues, or they can - from a group of atoms (-SO 3, -PO 4, -SiO 3) - these are complex residues.

In aqueous solutions, acid residues are not destroyed during exchange and substitution reactions:

H 2 SO 4 + CuCl 2 → CuSO 4 + 2 HCl

The word anhydride means anhydrous, that is, an acid without water. For example,

H 2 SO 4 - H 2 O → SO 3. Anoxic acids do not have anhydrides.

Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H 2 SO 4 - sulfuric; H 2 SO 3 - coal; H 2 SiO 3 - silicon, etc.

The element can form several oxygen acids. In this case, the indicated endings in the name of the acids will be when the element exhibits the highest valence (the acid molecule has a large content of oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “pure”: HNO 3 - nitric, HNO 2 - nitrous.

Acids can be obtained by dissolving anhydrides in water. If the anhydrides are insoluble in water, the acid can be obtained by the action of another stronger acid on the salt of the required acid. This method is typical for both oxygen and anoxic acids. Anoxic acids are also obtained by direct synthesis from hydrogen and non-metal, followed by dissolution of the resulting compound in water:

H 2 + Cl 2 → 2 HCl;

H 2 + S → H 2 S.

Solutions of the resulting gaseous substances HCl and H 2 S and are acids.

Under normal conditions, acids are both liquid and solid.

Chemical properties of acids

Acid solutions act on indicators. All acids (except silicic acid) dissolve well in water. Special substances - indicators allow you to determine the presence of acid.

Indicators are substances of complex structure. They change their color depending on the interaction with different chemicals. In neutral solutions, they have one color, in solutions of bases, another. When interacting with acid, they change their color: the methyl orange indicator turns red, the litmus indicator also turns red.

Interact with bases with the formation of water and salt, which contains an unchanged acid residue (neutralization reaction):

H 2 SO 4 + Ca (OH) 2 → CaSO 4 + 2 H 2 O.

Interact with based oxides with the formation of water and salt (neutralization reaction). The salt contains the acid residue of the acid that was used in the neutralization reaction:

H 3 PO 4 + Fe 2 O 3 → 2 FePO 4 + 3 H 2 O.

interact with metals. For the interaction of acids with metals, certain conditions must be met:

1. the metal must be sufficiently active with respect to acids (in the series of activity of metals, it must be located before hydrogen). The further to the left a metal is in the activity series, the more intensely it interacts with acids;

2. The acid must be strong enough (that is, capable of donating H + hydrogen ions).

During the course of chemical reactions of an acid with metals, a salt is formed and hydrogen is released (except for the interaction of metals with nitric and concentrated sulfuric acids):

Zn + 2HCl → ZnCl 2 + H 2;

Cu + 4HNO 3 → CuNO 3 + 2 NO 2 + 2 H 2 O.

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Acids can be classified according to different criteria:

1) The presence of oxygen atoms in the acid

2) Acid basicity

The basicity of an acid is the number of "mobile" hydrogen atoms in its molecule, capable of splitting off from the acid molecule in the form of hydrogen cations H + during dissociation, and also being replaced by metal atoms:

4) Solubility

5) Sustainability

7) Oxidizing properties

Chemical properties of acids

1. Ability to dissociate

Acids dissociate in aqueous solutions into hydrogen cations and acid residues. As already mentioned, acids are divided into well-dissociating (strong) and low-dissociating (weak). When writing the dissociation equation for strong monobasic acids, either one arrow pointing to the right () or an equal sign (=) is used, which actually shows the irreversibility of such dissociation. For example, the dissociation equation for strong hydrochloric acid can be written in two ways:

or in this form: HCl \u003d H + + Cl -

or in this: HCl → H + + Cl -

In fact, the direction of the arrow tells us that the reverse process of combining hydrogen cations with acidic residues (association) in strong acids practically does not occur.

In case we want to write the equation for the dissociation of a weak monobasic acid, we must use two arrows instead of the sign in the equation. This sign reflects the reversibility of the dissociation of weak acids - in their case, the reverse process of combining hydrogen cations with acidic residues is strongly pronounced:

CH 3 COOH CH 3 COO - + H +

Polybasic acids dissociate in steps, i.e. hydrogen cations are not detached from their molecules simultaneously, but in turn. For this reason, the dissociation of such acids is expressed not by one, but by several equations, the number of which is equal to the basicity of the acid. For example, the dissociation of tribasic phosphoric acid proceeds in three steps with the successive detachment of H + cations:

H 3 PO 4 H + + H 2 PO 4 —

H 2 PO 4 - H + + HPO 4 2-

HPO 4 2- H + + PO 4 3-

It should be noted that each next stage of dissociation proceeds to a lesser extent than the previous one. That is, H 3 PO 4 molecules dissociate better (to a greater extent) than H 2 PO 4 — ions, which, in turn, dissociate better than HPO 4 2- ions. This phenomenon is associated with an increase in the charge of acidic residues, as a result of which the strength of the bond between them and positive H + ions increases.

Of the polybasic acids, sulfuric acid is an exception. Since this acid dissociates well in both steps, it is permissible to write the equation of its dissociation in one stage:

H 2 SO 4 2H + + SO 4 2-

2. Interaction of acids with metals

The seventh point in the classification of acids, we indicated their oxidizing properties. It was pointed out that acids are weak oxidizers and strong oxidizers. The vast majority of acids (practically all except H 2 SO 4 (conc.) and HNO 3) are weak oxidizing agents, since they can show their oxidizing ability only due to hydrogen cations. Such acids can oxidize from metals only those that are in the activity series to the left of hydrogen, while the salt of the corresponding metal and hydrogen are formed as products. For example:

H 2 SO 4 (diff.) + Zn ZnSO 4 + H 2

2HCl + Fe FeCl 2 + H 2

As for strong oxidizing acids, i.e. H 2 SO 4 (conc.) and HNO 3, then the list of metals on which they act is much wider, and it includes both all metals up to hydrogen in the activity series, and almost everything after. That is, concentrated sulfuric acid and nitric acid of any concentration, for example, will oxidize even such inactive metals as copper, mercury, and silver. In more detail, the interaction of nitric acid and concentrated sulfuric acid with metals, as well as some other substances due to their specificity, will be considered separately at the end of this chapter.

3. Interaction of acids with basic and amphoteric oxides

Acids react with basic and amphoteric oxides. Silicic acid, since it is insoluble, does not react with low-active basic oxides and amphoteric oxides:

H 2 SO 4 + ZnO ZnSO 4 + H 2 O

6HNO 3 + Fe 2 O 3 2Fe (NO 3) 3 + 3H 2 O

H 2 SiO 3 + FeO ≠

4. Interaction of acids with bases and amphoteric hydroxides

HCl + NaOH H2O + NaCl

3H 2 SO 4 + 2Al (OH) 3 Al 2 (SO 4) 3 + 6H 2 O

5. Interaction of acids with salts

This reaction proceeds if a precipitate, a gas, or a substantially weaker acid than the one that reacts is formed. For example:

H 2 SO 4 + Ba(NO 3) 2 BaSO 4 ↓ + 2HNO 3

CH 3 COOH + Na 2 SO 3 CH 3 COONa + SO 2 + H 2 O

HCOONa + HCl HCOOH + NaCl

6. Specific oxidizing properties of nitric and concentrated sulfuric acids

As mentioned above, nitric acid in any concentration, as well as sulfuric acid exclusively in a concentrated state, are very strong oxidizing agents. In particular, unlike other acids, they oxidize not only metals that are up to hydrogen in the activity series, but also almost all metals after it (except platinum and gold).

For example, they are able to oxidize copper, silver and mercury. However, it should be firmly grasped the fact that a number of metals (Fe, Cr, Al), despite the fact that they are quite active (they are up to hydrogen), nevertheless, do not react with concentrated HNO 3 and concentrated H 2 SO 4 without heating on due to the passivation phenomenon - a protective film of solid oxidation products is formed on the surface of such metals, which does not allow molecules of concentrated sulfuric and concentrated nitric acids to penetrate deep into the metal for the reaction to proceed. However, with strong heating, the reaction still proceeds.

In the case of interaction with metals, the required products are always the salt of the corresponding metal and the acid used, as well as water. A third product is also always isolated, the formula of which depends on many factors, in particular, such as the activity of metals, as well as the concentration of acids and the temperature of the reactions.

The high oxidizing power of concentrated sulfuric and concentrated nitric acids allows them to react not only with practically all metals of the activity range, but even with many solid non-metals, in particular, with phosphorus, sulfur, and carbon. The table below clearly shows the products of the interaction of sulfuric and nitric acids with metals and non-metals, depending on the concentration:

7. Reducing properties of anoxic acids

All anoxic acids (except HF) can exhibit reducing properties due to the chemical element that is part of the anion, under the action of various oxidizing agents. So, for example, all hydrohalic acids (except HF) are oxidized by manganese dioxide, potassium permanganate, potassium dichromate. In this case, halide ions are oxidized to free halogens:

4HCl + MnO 2 MnCl 2 + Cl 2 + 2H 2 O

16HBr + 2KMnO 4 2KBr + 2MnBr 2 + 8H 2 O + 5Br 2

14НI + K 2 Cr 2 O 7 3I 2 ↓ + 2Crl 3 + 2KI + 7H 2 O

Among all hydrohalic acids, hydroiodic acid has the greatest reducing activity. Unlike other hydrohalic acids, even ferric oxide and salts can oxidize it.

6HI ​​+ Fe 2 O 3 2FeI 2 + I 2 ↓ + 3H 2 O

2HI + 2FeCl 3 2FeCl 2 + I 2 ↓ + 2HCl

Hydrosulfide acid H 2 S also has a high reducing activity. Even an oxidizing agent such as sulfur dioxide can oxidize it.