Task 32 at the Unified State Examination in Chemistry-2018 (the former task C2 of the “new type”) contains a description of an experiment consisting of sequentially conducted chemical reactions And laboratory methods separation of reaction products ( thought experiment).

In my experience, this task is difficult for many students. To a large extent, this is due to the increasingly academic nature of teaching chemistry in schools and courses, when insufficient attention is paid to the study of the features of work in the laboratory and the actual conduct of laboratory experiments.

Therefore, I decided to systematize and summarize the material on the so-called. "laboratory" chemistry. This article discusses examples of task 32 in the Unified State Examination in Chemistry-2018 (former task C2), with detailed analysis and solution analysis.

To complete this assignment, a good understanding of some topics in general chemistry and the chemistry of the elements is required, namely: main , chemical properties and obtaining, acids, and salts, and the relationship between different classes of inorganic substances; properties of simple substances - metals and non-metals; ; ; , , halogens.

  1. The solution obtained by the interaction of copper with concentrated nitric acid was evaporated and the precipitate was calcined. The gaseous products of the decomposition reaction are completely absorbed by water, and hydrogen is passed over the solid residue. Write the equations of the described reactions.

Analysis and decision.

"Keywords" - concentrated nitric acid and copper.

Copper is an inactive metal, it exhibits the properties of a reducing agent.

Keywords: " … The resulting product was sequentially treated with sulfur dioxide and barium hydroxide solution.". The sodium sulfate obtained in the previous step enters into an ion exchange reaction with barium hydroxide to precipitate barium sulfate (equation 4).

1) 2NaCl \u003d 2Na + Cl 2

2) 2Na + O 2 = Na 2 O 2

3) Na 2 O 2 + SO 2 = Na 2 SO 4

4) Na 2 SO 4 + Ba(OH) 2 = NaOH + BaSO 4

5.The decomposition products of ammonium chloride were successively passed through a heated tube containing copper (II) oxide, and then through a flask with phosphorus (V) oxide. Write the equations of the described reactions.

Analysis and decision.

Keywords: " Decomposition products of ammonium chloride... ". Ammonium chloride is a salt that decomposes when a solid salt is heated into gaseous ammonia and hydrogen chloride gas (equation 1)

Next, the products of reactions 2 and 3 are passed through a container with phosphorus (V) oxide. We analyze the possibility of a chemical reaction between substances. The simple substance copper is chemically inactive and does not react with phosphorus. The simple substance nitrogen is also chemically inactive; it does not react with phosphorus (V) oxide. But with acidic phosphorus (V) oxide, water vapor perfectly reacts with the formation of ortho-phosphoric acid (equation 4).

1) NH 4 Cl \u003d NH 3 + HCl

2) CuO + 2HCl = CuCl 2 + H2O

3) 3CuO + 2NH 3 = 3Cu + N 2 + 3H2O

4) 3H 2 O + P 2 O 5 \u003d 2H 3 PO 4

6. To a water-insoluble salt white, which occurs in nature in the form of a mineral widely used in construction and architecture, a solution of hydrochloric acid was added, as a result, the salt dissolved and a gas was released, which, when passed through lime water, precipitated a white precipitate; the precipitate dissolved upon further passing of the gas. When the resulting solution is boiled, a precipitate forms. Write the equations of the described reactions.

Analysis and decision.

It is well known from a school chemistry course that a white salt insoluble in water, which occurs in nature in the form of a mineral widely used in construction and architecture, is calcium carbonate CaCO 3 . Insoluble salts dissolve under the action of stronger acids, in this case, hydrochloric acid (Equation 1).

Produced gas passed through lime water Ca(OH)2. Carbon dioxide - typical acid oxide, which, when interacting with alkali, forms a salt - calcium carbonate (equation 2). Further the precipitate dissolved upon further passing of the gas. Here is a very important property: medium salts of polybasic acids under the action of an excess of acid form more acid salts . Calcium carbonate in excess of carbon dioxide forms a more acidic salt - calcium bicarbonate Ca (HCO 3) 2, which is highly soluble in water (equation 3).

The properties of acid salts are largely the sum of the properties of compounds forming acid salts. The properties of calcium bicarbonate are determined by the properties of its constituent compounds - carbonic acid H 2 CO 3 and calcium carbonate. It is easy to deduce that, when boiled, bicarbonate will decompose into calcium carbonate (distributed at higher temperatures, about 1200 degrees Celsius), carbon dioxide and water (equation 4).

1) CaCO 3 + 2HCl = CaCl 2 + CO 2 + H 2 O

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

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

4) Ca (HCO 3) 2 \u003d CaCO 3 + H 2 O + CO 2

7. Substance obtained from anode during the electrolysis of sodium iodide solution with inert electrodes, reacted with hydrogen sulfide. The resulting solid was fused with aluminum and the product was dissolved in water. Write the equations of the described reactions.

Analysis and decision.

The electrolysis of a sodium iodide solution with inert electrodes is described by the equation:

1. 2NaI + 2H 2 O \u003d 2NaOH + H 2 + I 2

2. I 2 0 + H 2 S -2 \u003d 2HI - + S 0

In this case, solid sulfur was formed. Sulfur reacts with aluminum when fused to form aluminum sulfide. Most non-metals react with metals to form binary compounds:

3. 3S 0 + 2Al 0 \u003d Al 2 +3 S 3 -2

The reaction product of aluminum with sulfur - aluminum sulfide - when dissolved in water, irreversibly decomposes into aluminum hydroxide and hydrogen sulfide:

4. Al 2 S 3 + 12H 2 O \u003d 2Al (OH) 3 + 3H 2 S

Such reactions are also called reactions. Cases of irreversible hydrolysis are considered in detail in.

8. The gas released during the interaction of hydrogen chloride with potassium permanganate reacts with iron. The reaction product was dissolved in water, and sodium sulfide was added thereto. The lighter insoluble matter formed was separated and reacted with hot concentrated nitric acid. Write the equations of the described reactions.

9. Chromium(III) sulfide was treated with water, which released gas and left an insoluble substance. A solution of caustic soda was added to this substance and gaseous chlorine was passed through, while the solution acquired a yellow color. The solution was acidified with sulfuric acid, as a result, the color changed to orange; the gas released during the treatment of sulfide with water was passed through the resulting solution, and the color of the solution changed to green. Write the equations of the described reactions.

Analysis and decision.

Keywords: " Chromium (III) sulfide was treated with water, while gas was released and an insoluble substance remained«. Chromium (III) sulfide decomposes under the action of water into hydroxide and hydrogen sulfide . The hydrolysis reactions of such compounds are discussed in detail in. (reaction 1)

1) Cr 2 S 3 + 6H 2 O \u003d 2Cr (OH) 3 + 3H 2 S

Key words: "... they added a solution of caustic soda and passed gaseous chlorine, while the solution acquired a yellow color." Under the action of chlorine in an alkaline environment, chromium +3 is oxidized to chromium +6 . Chromium +6 forms an acid oxide and hydroxide, in a solution of sodium hydroxide it forms a stable yellow salt - sodium chromate (reaction 2).

2) 2Cr +3 (OH) 3 + 3Cl 0 2 + 10NaOH = 2Na 2 Cr +6 O 4 + 6NaCl - + 8H 2 O

Next, the key words: The solution was acidified with sulfuric acid, as a result, the color changed to orange.«. Salts-chromates in an acidic medium turn into dichromates. Yellow sodium chromate in an acid medium turns into orange sodium dichromate (reaction 3). This is not OVR!

3) 2Na 2 CrO 4 + H 2 SO 4 = Na 2 Cr 2 O 7 + Na 2 SO 4 + H 2 O.

Further: “... the gas released during the treatment of sulfide with water was passed through the resulting solution, and the color of the solution changed to green.” Sodium dichromate is a strong oxidizing agent; when interacting with hydrogen sulfide, it is reduced to a trivalent chromium salt. Chromium (III) compounds are amphoteric; they form salts in an acidic environment. Salts of chromium (III) color the solution green (reaction 4).

4) Na 2 Cr +6 2 O 7 + 3H 2 S -2 + 4H 2 SO 4 = 3S 0 + Cr +3 2 (SO 4) 3 + Na 2 SO 4 + 7H 2 O

10. Obtaining a black and white image when photographing is based on the decomposition of an unknown metal salt under the action of light. When this metal is dissolved in dilute nitric acid, a colorless gas is released, which quickly changes its color to brown in air, and a salt is formed that interacts with sodium bromide to form a yellowish cheesy precipitate. The anion in the salt used in photography is an acid anion, which is formed simultaneously with sulfuric acid, when bromine water and sulfur dioxide react. Write the equations of the described reactions.

11. Sodium hydroxide solution was added dropwise to the solution obtained by reacting aluminum with dilute sulfuric acid until a precipitate formed. The white precipitate formed was filtered off and dried. The resulting substance was fused with sodium carbonate. Write the equations of the described reactions.

Analysis and decision.

Dilute sulfuric acid, when interacting with metals, behaves like ordinary mineral acid. Metals that are in the series of electrochemical activity to the left of hydrogen, when interacting with mineral acids, displace hydrogen:

1.2Al 0 + 3H + 2 SO 4 \u003d Al +3 2 (SO 4) 3 + 3H 0 2

Further, aluminum sulfate interacts with sodium hydroxide. The condition states that sodium hydroxide was added dropwise. This means that sodium hydroxide was in short supply, and aluminum sulfate was in significant excess. Under these conditions, a precipitate of aluminum hydroxide is formed:

2. Al 2 (SO 4) 3 + 6NaOH \u003d 2Al (OH) 3 + 3Na 2 SO 4

The white precipitate is aluminum hydroxide, insoluble in water. P On calcination, insoluble hydroxides decompose into water and the corresponding oxide :

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

The resulting substance, aluminum oxide, was fused with sodium carbonate. In the melt, less volatile oxides displace more volatile ones from salts.. A carbonate is a salt that corresponds to a volatile oxide, carbon dioxide. Accordingly, when alkali metal carbonates are fused with solid oxides (acidic and amphoteric), a salt corresponding to this oxide and carbon dioxide are formed:

4. Al 2 O 3 + Na 2 CO 3 \u003d 2NaAlO 2 + CO 2

12. Through a solution of copper chloride (II) with the help of graphite electrodes, a constant electricity. The electrolysis product released at the cathode was dissolved in concentrated nitric acid. The resulting gas was collected and passed through a sodium hydroxide solution. The gaseous product of electrolysis released at the anode was passed through a hot solution of sodium hydroxide. Write the equations of the described reactions.

13. A simple substance obtained by heating a mixture of calcium phosphate with coke and silicon oxide, dissolves in a solution of caustic potash. The escaping gaseous substance was burned, the combustion products were collected and cooled, and silver nitrate was added to the resulting solution. Write the equations of the described reactions.

14. The stinking liquid formed by the interaction of hydrogen bromide with potassium permanganate was separated and heated with iron filings. The reaction product was dissolved in water, and a cesium hydroxide solution was added thereto. The precipitate formed was filtered off and calcined. Write the equations of the described reactions.

15. Electric discharges were passed over the surface of the sodium hydroxide solution, while the air turned brown, and the color disappeared after a while. The resulting solution was carefully evaporated and found that the solid residue is a mixture of two salts. Keeping a mixture of salts in air leads to the formation of one substance. Write the equations of the described reactions.

Calcium is dissolved in water. When passing through the resulting solution of sulfur dioxide, a white precipitate is formed, which dissolves when passing an excess of gas. The addition of alkali to the resulting solution leads to the formation of a white precipitate. Write the equations of the described reactions.

When burned in air a simple substance yellow gas is formed with a pungent odor. This gas is also released when a certain mineral containing iron is burned in air. When dilute sulfuric acid acts on a substance consisting of the same elements as the mineral, but in a different ratio, a gas is released with a characteristic smell of rotten eggs. When the released gases interact with each other, the initial simple substance is formed. Write the equations of the described reactions.

Gaseous interaction product dry table salt with concentrated sulfuric acid was reacted with a solution of potassium permanganate. The evolved gas was passed through a solution of sodium sulfide. The resulting yellow precipitate is dissolved in a concentrated solution of sodium hydroxide. Write the equations of the described reactions.

The gas formed when hydrogen chloride is passed through a hot potassium chromate solution reacts with iron. The reaction product was dissolved in water, and sodium sulfide was added thereto. The lighter insoluble matter formed was separated and reacted with concentrated sulfuric acid by heating. Write the equations of the described reactions.

Two salts contain the same cation. The thermal decay of the first of them resembles a volcanic eruption, while a low-active colorless gas is released, which is part of the atmosphere. When the second salt interacts with a solution of silver nitrate, a white curdled precipitate is formed, and when it is heated with an alkali solution, a colorless poisonous gas with a pungent odor is released; this gas can also be obtained by reacting magnesium nitride with water. Write the equations of the described reactions.

An excess of sodium hydroxide solution was added to the aluminum sulfate solution. Hydrochloric acid was added in small portions to the resulting solution, and the formation of a bulky white precipitate was observed, which dissolved with further addition of acid. A solution of sodium carbonate was added to the resulting solution. Write the equations of the described reactions.

Electric discharges were passed over the surface of the sodium hydroxide solution poured into the flask, while the air in the flask turned brown, which disappeared after a while. The resulting solution was carefully evaporated and found that the solid residue is a mixture of two salts. When this mixture is heated, gas is released and only one substance remains. Write the equations of the described reactions.

Zinc oxide was dissolved in hydrochloric acid solution and the solution was neutralized by adding sodium hydroxide. The separated white gelatinous substance was separated and treated with an excess of alkali solution, while the precipitate completely dissolved. Neutralization of the resulting solution with an acid, such as nitric acid, leads to the re-formation of a gelatinous precipitate. Write the equations of the described reactions.

The substance obtained at the cathode during the electrolysis of a copper (II) chloride melt reacts with sulfur. The resulting product was treated with concentrated nitric acid and the evolved gas was passed through a barium hydroxide solution. Write the equations of the described reactions.

A mixture of calcium orthophosphate, coke and sand was heated in an electric furnace. One of the products of this reaction can ignite spontaneously in air. The solid combustion product of this substance was dissolved in water when heated, and gaseous ammonia was passed through the resulting solution. Write the equations of the described reactions.

The substance obtained at the cathode during the electrolysis of a solution of iron (II) chloride was fused with sulfur, and the product of this reaction was calcined. The resulting gas was passed through a solution of barium hydroxide. Write the equations of the described reactions.

A copper wire was introduced into heated concentrated sulfuric acid, and the escaping gas was passed through an excess of sodium hydroxide solution. The solution was carefully evaporated, the solid residue was dissolved in water and heated with powdered sulfur. The unreacted sulfur was separated by filtration, and sulfuric acid was added to the solution, while a precipitate was observed and a gas with a pungent odor was evolved. Write the equations of the described reactions.

After briefly heating an unknown orange powder, a spontaneous reaction begins, which is accompanied by a change in color to green, the release of gas and sparks. The solid residue was mixed with caustic potash and heated, the resulting substance was added to a dilute hydrochloric acid solution, and a green precipitate formed, which dissolves in an excess of acid. Write the equations of the described reactions.

Two salts color the flame purple. One of them is colorless, and when it is slightly heated with concentrated sulfuric acid, a liquid is distilled, in which copper dissolves; the last transformation is accompanied by the evolution of brown gas. When the second salt of the sulfuric acid solution is added to the solution, the yellow color of the solution changes to orange, and when the resulting solution is neutralized with alkali, the original color is restored. Write the equations of the described reactions.

An iron (III) chloride solution was subjected to electrolysis with graphite electrodes. The brown precipitate formed as a by-product of the electrolysis was filtered off and calcined. The substance formed on the cathode was dissolved in concentrated nitric acid by heating. The product separated at the anode was passed through a cold solution of potassium hydroxide. Write the equations of the described reactions.

The gas released during the interaction of hydrogen chloride with Berthollet salt was reacted with aluminum. The reaction product was dissolved in water and sodium hydroxide was added until the precipitation ceased, which was separated and calcined. Write the equations of the described reactions.

The unknown salt is colorless and turns the flame yellow. When this salt is slightly heated with concentrated sulfuric acid, a liquid is distilled off, in which copper dissolves; the last transformation is accompanied by the evolution of brown gas and the formation of a copper salt. During the thermal decomposition of both salts, one of the decomposition products is oxygen. Write the equations of the described reactions.

The substance obtained at the anode during the electrolysis of a melt of sodium iodide with inert electrodes was isolated and introduced into interaction with hydrogen sulfide. The gaseous product of the last reaction was dissolved in water, and ferric chloride was added to the resulting solution. The precipitate formed was filtered off and treated with hot sodium hydroxide solution. Write the equations of the described reactions.

Gases that are released when coal is heated in concentrated nitric and sulfuric acids are mixed with each other. The reaction products were passed through milk of lime. Write the equations of the described reactions.

A mixture of iron powder and a solid product obtained by the interaction of sulfur dioxide and hydrogen sulfide was heated without air. The resulting product was calcined in air. The resulting solid reacts with aluminum, releasing a large amount of heat. Write the equations of the described reactions.

A black substance was obtained by calcining the precipitate, which is formed by the interaction of solutions of sodium hydroxide and copper (II) sulfate. When this substance is heated with coal, a red metal is obtained, which dissolves in concentrated sulfuric acid. Write the equations of the described reactions.

A simple substance, a mixture of which is used in matches with Berthollet salt and ignites when rubbed, was burned in an excess of oxygen. The white solid resulting from combustion was dissolved in an excess of sodium hydroxide solution. The resulting salt with a solution of silver nitrate forms a bright yellow precipitate. Write the equations of the described reactions.

Zinc was dissolved in very dilute nitric acid, and an excess of alkali was added to the resulting solution, obtaining a clear solution. Write the equations of the described reactions.

The solution obtained by passing sulfur dioxide through bromine water was neutralized with barium hydroxide. The precipitate that formed was separated, mixed with coke, and calcined. When the calcination product is treated with hydrochloric acid, a gas with the smell of rotten eggs is released. Write the equations of the described reactions.

The substance formed when zinc powder was added to a solution of ferric chloride was separated by filtration and dissolved in hot dilute nitric acid. The solution was evaporated, the solid residue was calcined, and the evolved gases were passed through a solution of sodium hydroxide. Write the equations of the described reactions.

The gas released during heating of a solution of hydrogen chloride with manganese (IV) oxide was introduced into interaction with aluminum. The reaction product was dissolved in water and first an excess of sodium hydroxide solution was added, and then hydrochloric acid (excess). Write the equations of the described reactions.

A mixture of two colorless, colorless and odorless gases A and B was passed by heating over a catalyst containing iron, and the resulting gas B neutralized the hydrobromic acid solution. The solution was evaporated and the residue heated with caustic potash, as a result, a colorless gas B with a pungent odor was released. When gas B is burned in air, water and gas A are formed. Write the equations for the described reactions.

Sulfur dioxide was passed through a solution of hydrogen peroxide. Water was evaporated from the resulting solution, and magnesium shavings were added to the residue. The evolved gas was passed through a solution of copper sulphate. The black precipitate that formed was separated and fired. Write the equations of the described reactions.

A solution of hydrochloric acid was added to a water-insoluble white salt, which occurs in nature in the form of a mineral widely used in construction and architecture, as a result, the salt dissolved and a gas was released, which, when passed through lime water, precipitated a white precipitate, which dissolved with further passing gas. When an excess of lime water is added to the resulting solution, a precipitate forms. Write the equations of the described reactions.

When a certain mineral A, consisting of two elements, is burned, a gas is formed that has a characteristic pungent odor and decolorizes bromine water to form two strong acids in solution. When substance B, consisting of the same elements as mineral A, but in a different ratio, reacts with concentrated hydrochloric acid, a poisonous gas with the smell of rotten eggs is released. When the released gases interact with each other, a simple yellow substance and water are formed. Write the equations of the described reactions.

The substance released at the cathode during the electrolysis of a melt of sodium chloride was burned in oxygen. The resulting product was placed in a gasometer filled with carbon dioxide. The resulting substance was added to a solution of ammonium chloride and the solution was heated. Write the equations of the described reactions.

The nitric acid was neutralized with baking soda, the neutral solution was carefully evaporated, and the residue was calcined. The resulting substance was introduced into a solution of potassium permanganate acidified with sulfuric acid, and the solution became colorless. The nitrogen-containing reaction product was placed in a sodium hydroxide solution and zinc dust was added, and a gas with a sharp characteristic odor was released. Write the equations of the described reactions.

When salt solution A reacted with alkali, a gelatinous, water-insoluble blue substance was obtained, which was dissolved in a colorless liquid B to form a solution of blue color. The solid product remaining after careful evaporation of the solution was calcined; in this case, two gases were released, one of which is brown, and the second is part of the atmospheric air, and a black solid remains, which dissolves in liquid B with the formation of substance A. Write the equations of the described reactions.

White phosphorus dissolves in a solution of caustic potash with the release of a gas with a garlic odor, which ignites spontaneously in air. The solid product of the combustion reaction reacted with caustic soda in such a ratio that the resulting white substance contains one hydrogen atom; when the latter substance is calcined, sodium pyrophosphate is formed. Write the equations of the described reactions.

A solution of ferric chloride was treated with a solution of sodium hydroxide, the precipitate that formed was separated and heated. The solid reaction product was mixed with soda ash and calcined. Both sodium nitrate and sodium hydroxide were added to the remaining substance and heated at a high temperature for a long time. Write the equations of the described reactions.

The gas released during the interaction of hydrogen chloride with potassium permanganate was passed through a solution of sodium tetrahydroxoaluminate. The precipitate formed was filtered off, calcined, and the solid residue was treated with hydrochloric acid. Write the equations of the described reactions.

The nitric-hydrogen mixture was heated to a temperature of 500°C and under high pressure passed over an iron catalyst. The reaction products were passed through a solution of nitric acid until it was neutralized. The resulting solution was carefully evaporated, the solid residue was calcined, and the resulting gas was passed over copper while heating, resulting in a black solid. Write the equations of the described reactions.

Trivalent chromium hydroxide was treated with hydrochloric acid. Potash was added to the resulting solution, the precipitate was separated and added to a concentrated solution of caustic potash, as a result, the precipitate dissolved. After adding an excess of hydrochloric acid, a green solution was obtained. Write the equations of the described reactions.

The substance obtained at the anode during the electrolysis of a sodium iodide solution with inert electrodes was introduced into a reaction with potassium. The reaction product was heated with concentrated sulfuric acid and the evolved gas was passed through a hot solution of potassium chromate. Write the equations of the described reactions.

Ferrous oxide was heated with dilute nitric acid. The solution was carefully evaporated, the solid residue was dissolved in water, iron powder was added to the resulting solution, and after a while it was filtered. A solution of caustic potassium was added to the filtrate, the precipitate that formed was separated and left in air, while the color of the substance changed. Write the equations of the described reactions.

One of the substances formed when silicon oxide is fused with magnesium dissolves in alkali. The released gas was reacted with sulfur, and the product of their interaction was treated with chlorine. Write the equations of the described reactions.

The solid substance formed by the interaction of sulfur dioxide and hydrogen sulfide reacts with aluminum when heated. The reaction product was dissolved in dilute sulfuric acid, and potash was added to the resulting solution. Write the equations of the described reactions.

An unknown metal was burned in oxygen. The reaction product, interacting with carbon dioxide, forms two substances: a solid, which interacts with a solution of hydrochloric acid with the release of carbon dioxide, and a gaseous simple substance that supports combustion. Write the equations of the described reactions.

The product of the interaction of nitrogen and lithium was treated with water. The gas released as a result of the reaction was mixed with an excess of oxygen and, when heated, was passed over a platinum catalyst; the resulting gas mixture had a brown color. Write the equations of the described reactions.

Copper shavings were dissolved in dilute nitric acid and the solution was neutralized with caustic potash. The released blue substance was separated, calcined (the color of the substance changed to black), mixed with coke and re-calcined. Write the equations of the described reactions.

Phosphorus was burned in an excess of chlorine, the resulting solid was mixed with phosphorus and heated. The reaction product was treated with water, and a colorless gas with a pungent odor was released. The solution was added to a solution of potassium permanganate acidified with sulfuric acid, which became colorless as a result of the reaction. Write the equations of the described reactions.

Ferric chloride was treated with concentrated nitric acid on heating and the solution was carefully evaporated. The solid product was dissolved in water, potash was added to the resulting solution, and the precipitate that formed was separated and calcined. Gaseous hydrogen was passed over the resulting substance during heating. Write the equations of the described reactions.

An unknown salt, when interacting with a solution of silver nitrate, forms a white precipitate and colors the burner flame yellow. When concentrated sulfuric acid reacts with this salt, a poisonous gas is formed, which is highly soluble in water. Iron dissolves in the resulting solution, and a very light colorless gas is released, which is used to obtain metals, such as copper, from their oxides. Write the equations of the described reactions.

Magnesium silicide was treated with a solution of hydrochloric acid, and the escaping gas was burned. The solid reaction product was mixed with soda ash, the mixture was heated to melting and held for some time. After cooling, the reaction product (commonly used under the name "water glass") was dissolved in water and treated with a solution of sulfuric acid. Write the equations of the described reactions.

A gaseous mixture of ammonia and a large excess of air was passed on heating over platinum, and after a while the reaction products were absorbed by a solution of sodium hydroxide. After evaporation of the solution, a single product was obtained. Write the equations of the described reactions.

Soda ash was added to a solution of ferric chloride, and the precipitate that formed was separated and calcined. Carbon monoxide was passed over the resulting substance during heating, and the solid product of the last reaction was introduced into interaction with bromine. Write the equations of the described reactions.

The product of the interaction of sulfur with aluminum (the reaction proceeds when heated) was dissolved in cold dilute sulfuric acid, and potassium carbonate was added to the solution. The resulting precipitate was separated, mixed with caustic soda and heated. Write the equations of the described reactions.

Silicon (IV) chloride was heated in a mixture with hydrogen. The reaction product was mixed with magnesium powder, heated and treated with water; one of the formed substances ignites spontaneously in air. Write the equations of the described reactions.

A brown gas was passed through an excess of caustic potash solution in the presence of a large excess of air. Magnesium shavings were added to the resulting solution and heated; the liberated gas neutralized nitric acid. The resulting solution was carefully evaporated, the solid reaction product was calcined. Write the equations of the described reactions.

Iron scale was dissolved in concentrated nitric acid by heating. The solution was carefully evaporated and the reaction product was dissolved in water. Iron powder was added to the resulting solution, after a while the solution was filtered and the filtrate was treated with a solution of caustic potash, as a result, a light green precipitate formed, which quickly darkened in air. Write the equations of the described reactions.

A solution of aluminum chloride was added to a solution of soda ash, the released substance was separated and added to a solution of caustic soda. A solution of hydrochloric acid was added dropwise to the resulting solution until the formation of a precipitate ceased, which was separated and calcined. Write the equations of the described reactions.

Copper shavings were added to a solution of mercury (II) nitrate. After completion of the reaction, the solution was filtered and the filtrate was added dropwise to a solution containing sodium hydroxide and ammonium hydroxide. At the same time, a short-term formation of a precipitate was observed, which dissolved with the formation of a bright blue solution. When an excess of sulfuric acid solution was added to the resulting solution, a color change occurred. Write the equations of the described reactions.

The product of the interaction of magnesium phosphide with water was burned and the reaction products were absorbed by water. The resulting substance is used in industry to obtain double superphosphate from phosphorite. Write the equations of the described reactions.

The salt obtained by reacting zinc oxide with sulfuric acid was calcined at 800°C. The solid reaction product was treated with a concentrated alkali solution and carbon dioxide was passed through the resulting solution. Write the reaction equations for the described transformations.

Iron powder was added to the ferric chloride solution, and after a while the solution was filtered. Sodium hydroxide was added to the filtrate, the separated precipitate was separated and treated with hydrogen peroxide. To the resulting substance was added an excess of a solution of caustic potassium and bromine; as a result of the reaction, the color of bromine disappeared. Write the equations of the described reactions.

Copper(I) oxide was treated with concentrated nitric acid, the solution was carefully evaporated, and the solid residue was calcined. The gaseous reaction products were passed through a large amount of water and magnesium shavings were added to the resulting solution, as a result, a gas used in medicine was released. Write the equations of the described reactions.

Sulfur dioxide was passed through a solution of hydrogen peroxide. The solution was evaporated and copper shavings were added to the remaining liquid. The evolved gas was mixed with the gas formed by the interaction of iron (II) sulfide with a solution of hydrobromic acid. Write the equations of the described reactions.

When adding dilute hydrochloric acid to a yellow salt solution, which turns the flame purple, the color changes to orange-red. After neutralizing the solution with concentrated alkali, the color of the solution returned to its original color. When barium chloride is added to the resulting solution, a yellow precipitate forms. The precipitate was filtered off and silver nitrate solution was added to the filtrate. Write the equations of the described reactions.

Magnesium silicide was treated with a solution of hydrochloric acid, the reaction product was burned, the resulting solid was mixed with soda ash and heated to melt. After cooling the melt, it was treated with water and nitric acid was added to the resulting solution. Write the equations of the described reactions.

The insoluble substance formed when caustic soda was added to a solution of ferric chloride was separated and dissolved in dilute sulfuric acid. Zinc dust was added to the resulting solution, the precipitate was filtered off and dissolved in concentrated hydrochloric acid. Write the equations of the described reactions.

Aluminum nitrate was calcined, the reaction product was mixed with soda ash and heated to melt. The resulting substance was dissolved in nitric acid and the resulting solution was neutralized with an ammonia solution, while the isolation of a bulky gelatinous precipitate was observed. Write the equations of the described reactions.

Magnesium nitride was treated with excess water. When passing the evolved gas both through bromine water or through a neutral solution of potassium permanganate, and when it is burned, the same gaseous product is formed. Write the equations of the described reactions.

Chlorine water has the smell of chlorine. When alkalized, the smell disappears, and when hydrochloric acid is added, it becomes stronger than it was before. Write the equations of the described reactions.

The solid substance formed when malachite is heated was heated in a hydrogen atmosphere. The reaction product was treated with concentrated sulfuric acid and, after separation from the sulfuric acid, was added to a sodium chloride solution containing copper filings, and a precipitate formed as a result. Write the equations of the described reactions.

Phosphine was passed through a hot solution of concentrated nitric acid. The solution was neutralized with quicklime, the precipitate that formed was separated, mixed with coke and silica, and calcined. The reaction product, which glows in air, was heated in a sodium hydroxide solution. Write the equations of the described reactions.

Iron powder was dissolved in a large amount of dilute sulfuric acid, and air was passed through the resulting solution, and then a gas with the smell of rotten eggs. The insoluble salt formed was separated and dissolved in a hot solution of concentrated nitric acid. Write the equations of the described reactions.

Colorless gases are released when concentrated sulfuric acid is kept with both sodium chloride and sodium iodide. When these gases are passed through an aqueous solution of ammonia, salts are formed. Write the equations of the described reactions.

Magnesium powder was mixed with silicon and heated. The reaction product was treated with cold water and the evolved gas was passed through hot water. The resulting precipitate was separated, mixed with caustic soda and heated to melt. Write the equations of the described reactions.

One of the products of the interaction of ammonia with bromine, a gas that is part of the atmosphere, was mixed with hydrogen and heated in the presence of platinum. The resulting mixture of gases was passed through a solution of hydrochloric acid, and potassium nitrite was added to the resulting solution with slight heating. Write the equations of the described reactions.

The salt obtained by dissolving copper in dilute nitric acid was subjected to electrolysis using graphite electrodes. The substance released at the anode was introduced into interaction with sodium, and the resulting reaction product was placed in a vessel with carbon dioxide. Write the equations of the described reactions.

Unknown substance A dissolves in concentrated hydrochloric acid, the dissolution process is accompanied by the release of gas with the smell of rotten eggs; after neutralization of the solution with alkali, a volumetric precipitate of white (light green) color is formed. When substance A is fired, two oxides are formed. One of them is a gas that has a characteristic pungent odor and decolorizes bromine water with the formation of two strong acids in solution. Write the equations of the described reactions.

Magnesium was heated in a vessel filled with gaseous ammonia. The resulting substance was dissolved in a concentrated solution of hydrobromic acid, the solution was evaporated and the residue was heated until an odor appeared, after which an alkali solution was added. Write the equations of the described reactions.

Soda ash was added to a solution of trivalent chromium sulfate. The precipitate formed was separated, transferred to a sodium hydroxide solution, bromine was added, and heated. After neutralization of the reaction products with sulfuric acid, the solution acquires an orange color, which disappears after passing sulfur dioxide through the solution. Write the equations of the described reactions.

Quicklime was calcined with an excess of coke. The reaction product after treatment with water is used to absorb sulfur dioxide and carbon dioxide. Write the equations of the described reactions.

Ferrous sulfide was treated with a solution of hydrochloric acid, the escaping gas was collected and burned in the air. The reaction products were passed through an excess of potassium hydroxide solution, after which a solution of potassium permanganate was added to the resulting solution. Write the equations of the described reactions.

The solid product of the thermal decomposition of malachite was dissolved by heating in concentrated nitric acid. The solution was carefully evaporated and the solid residue was calcined to give a black substance, which was heated in excess ammonia (gas). Write the equations of the described reactions.

Red phosphorus was burned in an atmosphere of chlorine. The reaction product was treated with excess water and powdered zinc was added to the solution. The evolved gas was passed over heated ferrous oxide. Write the reaction equations for the described transformations.

The silvery-gray metal, which is attracted by a magnet, was brought into hot concentrated sulfuric acid and heated. The solution was cooled and caustic soda was added until the formation of an amorphous brown precipitate ceased. The precipitate was separated, calcined and dissolved in concentrated hydrochloric acid on heating. Write the equations of the described reactions.

Magnesium shavings were heated in a nitrogen atmosphere, and the reaction product was successively treated with boiling water, solutions of sulfuric acid, and barium nitrate. Write the equations of the described reactions.

During the thermal decomposition of salt A in the presence of manganese dioxide, a binary salt B and a gas that supports combustion and is part of the air were formed; when this salt is heated without a catalyst, salt B and a salt of a higher oxygen-containing acid are formed. When salt A reacts with hydrochloric acid, a yellow-green poisonous gas (a simple substance) is released and salt B is formed. Salt B colors the flame purple; when it interacts with a solution of silver nitrate, a white precipitate precipitates. Write the equations of the described reactions.

The precipitate obtained by adding caustic soda to the aluminum sulfate solution was separated, calcined, mixed with soda ash and heated to melt. After treatment of the residue with sulfuric acid, the initial aluminum salt was obtained. Write the equations of the described reactions.

The substance formed during the fusion of magnesium with silicon was treated with water, as a result a precipitate formed and a colorless gas was released. The precipitate was dissolved in hydrochloric acid, and the gas was passed through a solution of potassium permanganate, and two water-insoluble binary substances were formed. Write the equations of the described reactions.

The substance obtained by heating iron scale in a hydrogen atmosphere was introduced into hot concentrated sulfuric acid and heated. The resulting solution was evaporated, the residue was dissolved in water and treated with a barium chloride solution. The solution was filtered and a copper plate was added to the filtrate, which dissolved after a while. Write the equations of the described reactions.

Quicklime was "quenched" with water. A gas was passed into the resulting solution, which is released during the calcination of sodium bicarbonate, while the formation and subsequent dissolution of the precipitate were observed. Write the equations of the described reactions.

A mixture of nitrogen and hydrogen was successively passed over heated platinum and through a solution of sulfuric acid. Barium chloride was added to the solution, and after separating the precipitated precipitate, milk of lime was added and heated. Write the equations of the described reactions.

Give examples of interaction:

two acids

two bases

two acid salts

two acid oxides

Write the equations of the described reactions.

Solution medium salt, formed by passing sulfur dioxide through an alkali solution, was left in the air for a long time. The solid formed after evaporation of the solution was mixed with coke and heated to a high temperature. When hydrochloric acid is added to the solid product of the reaction, a gas with the smell of rotten eggs is released. Write the equations of the described reactions.

A solution of dilute sulfuric acid was added to a black powdery substance and heated. A solution of caustic soda was added to the resulting blue solution until the precipitation ceased. The precipitate was filtered off and heated. The reaction product was heated in an atmosphere of hydrogen, resulting in a red substance. Write the equations of the described reactions.

Red phosphorus was burned in an atmosphere of chlorine, and a small amount (several drops) of water was added to the reaction product. The liberated substance was dissolved in excess water, iron powder was added to the resulting solution, and the gaseous reaction product was passed over a heated copper plate oxidized to bivalent copper oxide. Write the reaction equations for the described transformations.

An iron (III) chloride solution was subjected to electrolysis with graphite electrodes. The brown precipitate formed during electrolysis was filtered off and dissolved in a sodium hydroxide solution, after which an amount of sulfuric acid was added that was necessary to form a clear solution. The product separated at the anode was passed through a hot potassium hydroxide solution. Write the equations of the described reactions.

Aluminum chloride was added to a solution of crystalline soda, the precipitate was separated and treated with a solution of caustic soda. The resulting solution was neutralized with nitric acid, the precipitate separated and calcined. Write the equations of the described reactions.

Ammonia was mixed with a large excess of air, heated in the presence of platinum, and after a while absorbed in water. Copper shavings added to the resulting solution dissolve with the release of brown gas. Write the equations of the described reactions.

When an acid solution A is added to manganese dioxide, a poisonous yellow-green gas is released. By passing the released gas through a hot solution of caustic potash, a substance is obtained that is used in the manufacture of matches and some other incendiary compositions. During the thermal decomposition of the latter in the presence of manganese dioxide, a salt is formed, from which, when interacting with concentrated sulfuric acid, it is possible to obtain the initial acid A, and a colorless gas, which is included in the composition of atmospheric air. Write the equations of the described reactions.

The product of the interaction of silicon with chlorine is easily hydrolyzed. When a solid hydrolysis product is fused with both caustic and soda ash, liquid glass is formed. Write the equations of the described reactions.

To the solution obtained by dissolving iron in hot concentrated hydrochloric acid, sodium hydroxide was added. The precipitate formed was separated, left in air for a long time, and then dissolved in dilute hydrochloric acid. Write the equations of the described reactions.

When heated, an orange substance decomposes; decomposition products include a colorless gas and a green solid. The released gas reacts with lithium even with slight heating. The product of the latter reaction interacts with water, and a gas with a pungent odor is released, which can restore metals, such as copper, from their oxides. Write the equations of the described reactions.

The rotten-egg-smelling gas was passed through concentrated sulfuric acid at room temperature. The resulting precipitate was separated and treated with hot concentrated nitric acid; the evolved gas was dissolved in a large amount of water, and a piece of copper was added to the resulting solution. Write the reaction equations for the described transformations.

The salt obtained by dissolving iron in hot concentrated sulfuric acid was treated with an excess of sodium hydroxide solution. The brown precipitate formed was filtered off and dried. The resulting substance was fused with iron. Write the equations of the described reactions.

Zinc metal was added to concentrated sulfuric acid. The resulting salt was isolated, dissolved in water, and barium nitrate was added to the solution. After separation of the precipitate, magnesium shavings were added to the solution, the solution was filtered, the filtrate was evaporated and calcined. Write the equations of the described reactions.

An unknown red substance was heated in chlorine and the reaction product was dissolved in water. Alkali was added to the resulting solution, the resulting blue precipitate was filtered off and calcined. When heating the calcination product, which has a black color, with coke, starting material Red. Write the equations of the described reactions.

Iodine was heated with an excess of phosphorus and the reaction product was treated with a small amount of water. The gaseous reaction product was completely neutralized with sodium hydroxide solution and silver nitrate was added to the resulting solution. Write the equations of the described reactions.

Iron burned in chlorine. The reaction product was dissolved in water, and iron filings were added to the solution. After some time, the solution was filtered and sodium sulfide was added to the filtrate. The precipitate that formed was separated and treated with 20% sulfuric acid to give an almost colorless solution. Write the equations of the described reactions.

The gas released when solid salt is heated with concentrated sulfuric acid was passed through a solution of potassium permanganate. The gaseous reaction product was taken up in cold sodium hydroxide solution. After adding hydroiodic acid to the resulting solution, a pungent odor appears and the solution acquires a dark color. Write the equations of the described reactions.

A gas was passed through the solution obtained by slaking lime, which is formed when quicklime is obtained from limestone; the result is a white precipitate. Under the action of acetic acid on the resulting precipitate, the same gas is released that is formed during the calcination of calcium carbonate. Write the equations of the described reactions.

A red substance, which is used in the manufacture of matches, was burned in excess air and the reaction product was dissolved in a large amount of water when heated. After neutralizing the resulting solution with baking soda, silver nitrate was added to it. Write the equations of the described reactions.

A gas was passed through a solution of sodium bromide, which is released during the interaction of hydrochloric acid with potassium permanganate. After completion of the reaction, the solution was evaporated, the residue was dissolved in water and subjected to electrolysis with graphite electrodes. The gaseous products of the reaction were mixed with each other and illuminated, and the result was an explosion. Write the equations of the described reactions.

The gas formed during the combustion of coke was in contact with hot coal for a long time. The reaction product was successively passed through a layer of heated iron ore and quicklime. Write the equations of the described reactions.

Copper shavings were added to the heated concentrated sulfuric acid, and the released gas was passed through a solution of caustic soda (excess). The reaction product was isolated, dissolved in water, and heated with sulfur, which dissolved as a result of the reaction. Dilute sulfuric acid was added to the resulting solution. Write the equations of the described reactions.

Hydrochloric acid was added to solutions of substances L and B, which color the flame yellow, hydrochloric acid: When a solution of substance A reacts with hydrochloric acid, a colorless gas with an unpleasant odor is released, which forms a black precipitate when passed through a solution of lead (II) nitrate. When a solution of substance B is heated with hydrochloric acid, the color of the solution changes from yellow to green and a yellow-green poisonous gas with a characteristic pungent odor is released. When barium nitrate is added to a solution of substance B, a yellow precipitate forms. Write the equations of the described reactions.

A solution of hydrochloric acid was carefully added to the pyrolusite, and the escaping gas was passed into a beaker half-filled with a cold solution of caustic potash. After the end of the reaction, the glass was covered with cardboard and left, while the glass was illuminated by the sun's rays; after a while, a smoldering splinter was brought into the glass, which flared up brightly. Write the equations of the described reactions.

The precipitate obtained by the interaction of an aluminum salt solution and alkali was calcined. The reaction product was dissolved in a concentrated hot alkali solution. Carbon dioxide was passed through the resulting solution, resulting in a precipitate. Write the equations of the described transformations.

The black powder, which was formed during prolonged heating of a red metal in excess air, was dissolved in 10% sulfuric acid and a blue solution was obtained. Alkali was added to the solution, and the precipitate that formed was separated and dissolved in an excess of ammonia solution. Write the equations of the described reactions.

Phosphorus was added to the solid that forms when phosphorus is burned in excess chlorine, and the mixture is heated. The reaction product was treated with a small amount of hot water, and a solution of potassium permanganate acidified with sulfuric acid was added to the resulting solution. Write the equations of the described reactions.

Carbon dioxide was passed through barite water. Barium hydroxide was added to the resulting solution, the reaction product was separated and dissolved in phosphoric acid. Write the equations of the described reactions.

Zinc nitrate was calcined, the reaction product was treated with sodium hydroxide solution when heated. Carbon dioxide was passed through the resulting solution until the precipitation ceased, after which it was treated with an excess of concentrated ammonia, and the precipitate dissolved. Write the equations of the described reactions.

Two vessels contain solutions of unknown substances. When the first substance of barium chloride is added to the solution, a white precipitate forms, insoluble in water and acids. A white precipitate also occurs when a silver nitrate solution is added to a sample taken from the second vessel. When a sample of the first solution with sodium hydroxide is heated, a sharp odor is released from the gas. When the second solution reacts with sodium chromate, a yellow precipitate is formed. Write the equations of the described reactions.

Sulfur dioxide was dissolved in water and the solution was neutralized by adding sodium hydroxide. Hydrogen peroxide was added to the resulting solution, and after the reaction was completed, sulfuric acid was added. Write the equations of the described reactions.

Zinc was dissolved in very dilute nitric acid, the resulting solution was carefully evaporated and the residue was calcined. The reaction products were mixed with coke and heated. Make the reaction equations of the described transformations.

Substances released at the cathode and anode during the electrolysis of sodium iodide solution with graphite electrodes react with each other. The reaction product reacts with concentrated sulfuric acid to release gas, which is passed through a solution of potassium hydroxide. Write the equations of the described reactions.

The substance that is formed during the electrolysis of a bauxite melt in cryolite dissolves both in a hydrochloric acid solution and in an alkali solution with the release of the same gas. When the resulting solutions are mixed, a bulk white precipitate is formed. Write the equations of the described reactions.

Concentrated hydrochloric acid was added to lead (IV) oxide while heating. The escaping gas was passed through a heated solution of caustic potash. The solution was cooled, the oxygenated acid salt was filtered off and dried. When the resulting salt is heated with hydrochloric acid, poisonous gas is released, and when it is heated in the presence of manganese dioxide, a gas is released, which is also part of the atmosphere. Write the equations of the described reactions.

The brown precipitate obtained by reacting sodium sulfite with an aqueous solution of potassium permanganate was filtered off and treated with concentrated sulfuric acid. When heated, the gas released reacts with aluminum, and the resulting substance reacts with a solution of hydrochloric acid. Write the reaction equations for the described transformations.

Calcium was heated in a hydrogen atmosphere. The reaction product was treated with water, the evolved gas was passed over heated zinc oxide, and soda ash was added to the solution. Write the equations of the described reactions.

Silver nitrate was calcined and the solid reaction product was heated in oxygen. The resulting substance dissolves in an excess of concentrated ammonia. When passing through the resulting solution of hydrogen sulfide, a black precipitate is formed. Write the equations of the described reactions.

The solid that forms when phosphorus and phosphorus pentachloride are heated is dissolved in a large amount of water. Part of the resulting solution was added to a solution of potassium permanganate acidified with sulfuric acid, while the latter became colorless. Write the equations of the described reactions.

Several granules of zinc were introduced into a vessel with concentrated sulfuric acid. The escaping gas was passed through a solution of lead (II) acetate, the precipitate was separated, subjected to roasting, and the resulting gas was introduced into interaction with an aqueous solution of potassium permanganate. Write the equations of the described reactions.

Several granules of zinc were dissolved by heating in a solution of sodium hydroxide. Nitric acid was added in small portions to the resulting solution until a precipitate formed. The precipitate was separated, dissolved in dilute nitric acid, the solution was carefully evaporated and the residue was calcined. Write the equations of the described reactions.

The gas released when copper is dissolved in hot concentrated nitric acid can interact both with the gas released when copper is treated with hot concentrated sulfuric acid and with copper. Write the equations of the described reactions.

An iron (III) chloride solution was subjected to electrolysis with graphite electrodes. A brown precipitate formed (a by-product of electrolysis) was filtered off, calcined and fused with the substance formed on the cathode. Another substance, also released at the cathode, was reacted with the product released during electrolysis at the anode; The reaction proceeds under illumination and with an explosion. Write the equations of the described reactions.

Water-insoluble white salt, which meets ­ found in nature in the form of a mineral widely used in construction and architecture, calcined at 1000°C. Water was added to the solid residue after cooling, and the gaseous product of the decomposition reaction was passed through the resulting solution, as a result, a white precipitate formed, which dissolved upon further passing of the gas. Write the equations of the described reactions.

Pharmacopoeial preparations of iodides are

sodium iodide

Natrii iodidum Nal M. m. 149.89

Potassium iodide Kalii iodidum KI M. m. 166.01

Both preparations are white crystalline powders.

Iodides are used as carriers of iodine in hyperthyroidism,

endemic goiter.

If food or water does not contain enough iodine, as is the case in some mountainous areas, then the local population develops a disease - cretinism or goiter disease. Assign iodides in the form of solutions (potions)" for oral administration.

Methods for obtaining halides. Sodium chloride is the only one of the halides that is widely distributed in nature in the form of massive deposits of rock salt. It is the main source for obtaining a pharmacopoeial preparation. Aqueous salt solutions are evaporated, after which sodium chloride is purified from the impurities accompanying it. Ultimately, sodium chloride is recrystallized from water saturated with concentrated hydrochloric acid, in which it is poorly soluble.

A purer preparation can be obtained by treating sodium carbonate or potassium x. including hydrochloric acid.

The accompanying product of the reaction (CO2) is volatile and therefore sodium (potassium) chlorides are pure.

Bromides and iodides are obtained in exactly the same way. In industry, they are obtained as follows: iron shavings are treated with water and bromine or iodine, respectively, is added. In this case, iron bromide (iodide) (FeBr 2 or Fel 2) is formed. Then Br,(I,) is added to the reaction mass again.



Precipitates of iron hydroxides are filtered off. Sodium bromide or, respectively, sodium iodide crystallizes out of the filtrate after evaporation.

To obtain potassium bromide and potassium iodide, potash K2CO3 is taken instead of soda.

The authenticity of all these drugs (chlorides, bromides, iodides) is determined by the cation Na + and K + and by the corresponding anion C1 ~, Br ~, I -.

Sodium ion is usually detected by the yellow color of the flame. Of the chemical reactions, HF X leads to a reaction with zinccuranyl acetate - in the presence of Na +, a yellow crystalline precipitate is released.


Potassium ion is determined by the violet color of the flame of the burner, and when viewed through blue glass, the flame appears to be colored purple-red.

Of the chemical reactions used:

a) reaction with tartaric acid in the presence of sodium acetate.


To avoid the dissolution of the precipitate of potassium hydrotartrate in the formed mineral acid (HC1), it is bound with sodium acetate;

b) reaction with a solution of sodium cobaltinitrite (hexanite-

sodium rocobalt).


The reaction is carried out in an acetic acid medium by rubbing with a stick on the walls of the vessel.

This reaction can detect potassium ion only in the absence of NH4 + -hohob, which also precipitate with this reagent. Therefore, before investigating potassium salts with this reaction, they should be calcined to remove possible impurities of ammonium salts.

To confirm the authenticity of anions C1 -, Br ~, I - GF X leads two main reactions:

a) reaction with a solution of silver nitrate in the presence of nitric acid; when chlorides, bromides, iodides are exposed to a solution of silver nitrate in the presence of nitric acid, cheesy precipitates are formed, respectively:


The reaction is carried out in the presence of nitric acid, which does not dissolve silver halide precipitates.

Since silver chlorides and bromides are sometimes difficult to distinguish by color, it is recommended to test the solubility of these precipitates in ammonia and ammonium carbonate solutions.

Silver chloride readily dissolves in dilute solutions of ammonia and ammonium carbonate to form the corresponding soluble complexes.


Silver bromide is hardly soluble in dilute solutions of ammonia and dissolves only in concentrated solutions, and does not dissolve at all in solution

Silver iodide does not dissolve either in ammonia solutions or in solution (MHN-CO3.

b) oxidation reaction of halide ions (C1~, Br~, I -) to elemental halogen; halide ions in an acidic environment are reducing agents and are themselves capable of being oxidized to a free halogen. This property is used to determine the authenticity of bromides and iodides.

To a solution of bromide or iodide (NaBr, Nal) add a mineral acid, such as hydrochloric acid, chloroform and an oxidizing agent. Usually, in the case of bromides, chloramine is added as an oxidizing agent, and in the case of iodides, sodium nitrite NaN0 2 or ferric chloride FeCl 3 is added. The reaction mass is shaken and allowed to settle. The chloroform layer in the case of bromides turns yellow (Br 2), and in the case of iodides, it turns purple (1 2).


Chlorides (NaCl, KCI) are also oxidized to free chlorine, but since chlorine is volatile, this reaction is not convenient for authenticating chlorides and is not recommended by GF X.

Often, to open bromides and iodides, bromates (NaBrOz) and, accordingly, iodates (NaI0 3) are used, which, being oxidizing agents, oxidize Br~ and 1~ in an acidic environment to free bromine and, accordingly, iodine. The reaction is carried out in the presence of chloroform, which turns yellow (Br 2) and, accordingly, violet (b).


Purity test. For sodium and potassium chlorides, GF X requires the absence of impurities of magnesium, barium, and ammonium salts.

In sodium chloride, impurities of potassium salts are not allowed, and in potassium chloride - sodium salts, since potassium and sodium are antagonists in action.

Impurities such as calcium, iron, heavy metals, sulfates, arsenic, GF X are allowed in sodium and potassium chloride preparations within the limits of the standards, since the permissible limit of these impurities does not affect the therapeutic effect of the preparations and does not cause any side effects.

In bromides, impurities of barium, calcium, bromates, iodides (toxic) are not allowed.

The admixture of soluble barium and calcium salts is determined by adding dilute sulfuric acid to the preparation solution. In the presence of Ba 2+ and Ca 2+, the solution will become cloudy due to the formation of insoluble calcium and barium salts (CaSO4 and BaSO-i).

The admixture of iodides is determined by adding an oxidizing agent, such as ferric chloride, to the solution of the preparation.


When chloroform is added, the released iodine will turn it purple.

Bromates are the most dangerous impurity due to their toxicity. You can find them in bromides by adding hydrochloric acid. In the presence of an admixture of bromates, free bromine will be released, which will color the solution yellow.


Impurities of sulfates, heavy metals and arsenic are allowed in bromides within the standards.

Iodides may contain impurities of carbonates, cyanides, nitrates, iodates, soluble barium salts. All these impurities are poisonous and therefore their content in preparations is not allowed.

The admixture of nitrates is discovered by reducing them to ammonia, which is detected organoleptically or by the blue discoloration of wet red litmus paper.


The admixture of cyanides is determined by the formation of Prussian blue.


Quantitative content of chlorides and bromides GF X recommends to determine the method of argentometry (according to the Mohr method). An accurate sample of the drug in a neutral or slightly alkaline medium is titrated with a solution of silver nitrate to a brownish-red color of the precipitate according to the indicator KrCr0 4 .


The reaction with bromides proceeds similarly.

Iodides cannot be determined by the Mohr method, since their titration is accompanied by the formation of colloidal systems of silver iodide and adsorption, which makes it difficult to establish the end point of the titration. Therefore, iodides are determined by titration with silver nitrate using adsorption indicators, which are salts of weak organic acids, such as the di-sodium salt of fluorescein (I) or sodium eosinate (II).


As iodide is titrated with silver nitrate, a colloidal Agl precipitate is formed, the particles of which have a high adsorption capacity. Positively charged, they adsorb negatively charged indicator anions on their surface and, at the equivalent point, cause a change in the color of the surface of the Agl precipitate from yellow to pink.

Storage. Chlorides, bromides, iodides should be stored under conditions that prevent the oxidation of these drugs: in well-corked jars, in a dry place. Iodides and bromides are usually stored in orange glass jars, as light stimulates the oxidation process.

Iodine is a chemical element of Group VII of Mendeleev's periodic system. Atomic number - 53. Relative atomic mass 126.90450.0001. Halogen. Of the naturally occurring halogens, it is the heaviest, unless, of course, we count the radioactive short-lived astatine. Almost all natural iodine consists of atoms of a single isotope with a mass number of 127, its content in the earth's crust is 4.10 5% by weight. Radioactive iodine - 125 is formed during natural radioactive transformations. Of the artificial isotopes of iodine, the most important are iodine -131 and iodine -133: they are mainly used in medicine.

I 2 - halogen. Dark gray crystals with a metallic sheen. Volatile It is poorly soluble in water, well - in organic solvents (with a purple or brown coloring of the solution) or in water with the addition of salts - iodides. Weak oxidizing and reducing agent. Reacts with concentrated sulfuric and nitric acids, metals, non-metals, alkalis, hydrogen sulfide. Forms compounds with other halogens.

The elemental iodine molecule, like other halogens, consists of two atoms. Iodine - the only one of the halogens - is in a solid state under normal conditions. Beautiful dark blue crystals of iodine are most similar to graphite. A distinctly pronounced crystalline structure, the ability to conduct electric current - all these "metallic" properties are characteristic of pure iodine.

Distribution in nature

The average content of iodine in the earth's crust is 4 * 10 -5% by weight. In the mantle and magmas and in the rocks formed from them (granites, basalts), iodine compounds are scattered; the deep minerals of iodine are unknown. The history of iodine in the earth's crust is closely connected with living matter and biogenic migration. In the biosphere, processes of its concentration are observed, especially by marine organisms (algae, sponges). There are 8 known supergene minerals of iodine that are formed in the biosphere, but they are very rare. The main reservoir of iodine for the biosphere is the World Ocean (1 liter contains on average 5 * 10 -5 grams of iodine). From the ocean, iodine compounds dissolved in drops of sea water enter the atmosphere and are carried by winds to the continents. Areas remote from the ocean or fenced off from sea winds by mountains are depleted in iodine. Iodine is readily adsorbed by organic matter in soils and sea silts. With the compaction of these silts and the formation of sedimentary rocks, desorption occurs, some of the iodine compounds pass into groundwater. This is how the iodine-bromine waters used for the extraction of iodine are formed, especially characteristic of the regions oil fields(in some places 1 liter of these waters contains over 100 mg of iodine).

Physical and chemical properties

The density of iodine is 4.94 g/cm3, t pl 113.5 °C, t bp 184.35 °C. The molecule of liquid and gaseous iodine consists of two atoms (I 2). A noticeable dissociation of I 2 2I is observed above 700 °C, and also under the action of light. Already at ordinary temperature, iodine evaporates, forming a sharp-smelling purple vapor. With weak heating, iodine sublimates, settling in the form of shiny thin plates; this process serves to purify iodine in laboratories and in industry. Iodine is poorly soluble in water (0.33 g / l at 25 ° C), well - in carbon disulfide and organic solvents (benzene, alcohol), as well as in aqueous solutions of iodides.

The configuration of the outer electrons of the iodine atom is 5s2 5p5. In accordance with this, it exhibits variable valency (oxidation state) in compounds: -1 (in HI, KI); +1 (in HIO, KIO); +3 (in ICl 3); +5 (in HIO 3 , KIO 3); and +7 (in HIO 4 , KIO 4). Chemically, iodine is quite active, although to a lesser extent than chlorine and bromine. With metals, iodine interacts vigorously with light heating, forming iodides (Hg + I 2 \u003d HgI 2). Iodine reacts with hydrogen only when heated and not completely, forming hydrogen iodide. Elemental iodine is an oxidizing agent less powerful than chlorine and bromine. Hydrogen sulfide H 2 S, sodium thiosulfate Na 2 S 2 O 3 and other reducing agents reduce it to I- (I 2 + H 2 S = S + 2НI). Chlorine and other strong oxidizing agents in aqueous solutions convert it to IO 3 -. When dissolved in water, iodine partially reacts with it; in hot aqueous solutions of alkalis, iodide and iodate are formed. Adsorbed on starch, iodine turns it dark blue; this is used in iodometry and qualitative analysis for the detection of iodine. Iodine vapors are poisonous and irritate mucous membranes. Iodine has a cauterizing and disinfecting effect on the skin. Spots from iodine are washed off with solutions of soda or sodium thiosulfate.

Receipt

The raw material for the industrial production of iodine in Russia is oil drilling water; abroad - seaweed, as well as mother solutions of Chilean (sodium) nitrate, containing up to 0.4% iodine in the form of sodium iodate. To extract iodine from oil waters (usually containing 20 - 40 mg / l of iodine in the form of iodides), they are first treated with chlorine or nitrous acid. The released iodine is either adsorbed by active carbon or blown out with air. Iodine adsorbed by coal is treated with caustic alkali or sodium sulfite. From the reaction products, free iodine is isolated by the action of chlorine or sulfuric acid and an oxidizing agent, such as potassium dichromate. When blown with air, the iodine is absorbed by a mixture of sulfur dioxide with water vapor and then the iodine is displaced by chlorine. Raw crystalline iodine is purified by sublimation.

Iodine in the body

Iodine is an essential trace element for animals and humans. In soils and plants of the taiga-forest non-chernozem, dry steppe, desert and mountain biogeochemical zones. Iodine is contained in insufficient quantities or is not balanced with some other trace elements (Ca, Mn, Cu); this is associated with the spread of endemic goiter in these areas. The average content of iodine in soils is about 3*10 -4%, in plants about 2*10 -5%. In the surface drinking water little iodine (from 10 -7 to 10 -9%). In coastal areas, the amount of iodine in 1 m3 of air can reach 50 micrograms, in continental and mountainous areas it is 1 or even 0.2 micrograms.

The absorption of iodine by plants depends on the content of its compounds in soils and on the type of plants. Some organisms (the so-called iodine concentrators, for example, seaweeds - fucus, kelp, phyllophora, accumulate up to 1% iodine, some sponges - up to 8.5% (in the skeletal substance of spongin). Algae that concentrate iodine are used for its industrial production. Iodine enters the animal body with food, water, air.The main source of iodine is vegetable products and feed.Iodine is absorbed in the anterior sections of the small intestine.In the human body, 20 to 50 mg of iodine accumulates, including about 10 - 25 mg in the muscles. mg, in the thyroid gland at a rate of 6 - 15 mg Using radioactive iodine (I 131 and I 125) it has been shown that in the thyroid gland iodine accumulates in the mitochondria of epithelial cells and is part of the all- and monoiodotyrosines formed in them, which are condensed into hormone tetraiodothyronine (thyroxine).Iodine is excreted from the body mainly through the kidneys (up to 70 - 80%), mammary, salivary and sweat glands, partly with bile.

In various biogeochemical provinces, the iodine content in the daily ration varies (from 20 to 240 mcg for a person, from 20 to 400 mcg for a sheep). An animal's need for iodine depends on its physiological state, season, temperature, adaptation of the body to the iodine content in the environment. The daily requirement for iodine in humans and animals is about 3 μg per 1 kg of body weight (increases during pregnancy, increased growth, cooling). The introduction of iodine into the body increases the basal metabolism, enhances oxidative processes, and tones the muscles.

Yod and man

The human body not only does not need large quantities iodine, but also maintains a constant concentration in the blood (10 -5 - 10 -6%) of iodine, the so-called iodine mirror of blood. From total iodine in the body is about 25 mg, more than half is in the thyroid gland. Almost all of the iodine contained in this gland is part of various derivatives of tyrosine, a thyroid hormone, and only a small part of it, about 1%, is in the form of inorganic iodine I 1-.

Large doses of elemental iodine are dangerous: a dose of 2-3 g is lethal. At the same time, in the form of iodide, oral administration in large doses is allowed.

In medical practice, organioiodine compounds are used for X-ray diagnostics. Sufficiently heavy nuclei of iodine atoms absorb x-rays. When such a diagnostic tool is introduced into the body, exceptionally clear x-rays of individual sections of tissues and organs are obtained.

Iodine in medicine

The antiseptic properties of iodine in surgery were first used by the doctor Buane. Oddly enough, the simplest dosage forms of iodine - aqueous and alcoholic solutions - did not find application in surgery for a very long time, although back in 1865 - 1866. the great Russian surgeon N.I. Pirogov used iodine tincture in the treatment of wounds.

Preparations containing iodine have antibacterial and antifungal properties, they also have an anti-inflammatory and distracting effect; they are used externally for the disinfection of wounds, preparation of the surgical field. When taken orally, iodine preparations affect the metabolism, enhance the function of the thyroid gland. Small doses of iodine (microiodine) inhibit the function of the thyroid gland, acting on the formation of thyroid-stimulating hormone in the anterior lobes of the pituitary gland. Since iodine affects protein and fat (lipid) metabolism, it has found application in the treatment of atherosclerosis, as it lowers blood cholesterol; also increases the fibrinolytic activity of the blood.

For diagnostic purposes, radiopaque agents containing iodine are used. With prolonged use of iodine preparations and with increased sensitivity to them, iodism may occur - runny nose, urticaria, angioedema, lacrimation, acne (iododerma). Iodine preparations should not be taken with pulmonary tuberculosis, pregnancy, kidney disease, chronic pyoderma, hemorrhagic diathesis, urticaria.

radioactive iodine

Artificially radioactive isotopes of iodine - I 125 , I 131 , I 132 and others are widely used in biology and especially in medicine to determine the functional state of the thyroid gland and treat a number of its diseases. The use of radioactive iodine in diagnostics is associated with the ability of iodine to selectively accumulate in the thyroid gland; use for medicinal purposes is based on the ability - radiation of radioisotopes of iodine to destroy the secretory cells of the gland. When the environment is contaminated with nuclear fission products, radioactive isotopes of iodine are quickly included in the biological cycle, eventually getting into milk and, consequently, into the human body.

Especially dangerous is their penetration into the body of children, whose thyroid gland is 10 times smaller than that of adults and, moreover, has greater radiosensitivity. In order to reduce the deposition of radioactive isotopes of iodine in the thyroid gland, it is recommended to use stable I. preparations (100–200 mg per dose). Radioactive iodine is rapidly and completely absorbed in the gastrointestinal tract and deposited selectively in the thyroid gland. Its absorption depends on the functional state of the gland. Relatively high concentrations of radioisotopes of iodine are also found in the salivary and mammary glands and the mucosa of the gastrointestinal tract. Radioactive iodine not absorbed by the thyroid gland is almost completely and relatively quickly excreted in the urine.

The use of iodine

Iodine and its compounds are mainly used in medicine and analytical chemistry, as well as in organic synthesis and photography. In industry, the use of iodine is still insignificant in volume, but very promising. Thus, the production of high-purity metals is based on the thermal decomposition of iodides.

Relatively recently, iodine began to be used in the production of incandescent lamps operating on the iodine-tungsten cycle. Iodine combines with particles of tungsten that have evaporated from the lamp coil, forming a WI 2 compound, which decomposes when it gets on the heated coil. In this case, tungsten returns to the spiral again, and iodine again combines with the evaporated tungsten. Iodine, as it were, takes care of the preservation of the tungsten coil and thereby significantly increases the operating time of the lamp.

Also, 0.6% iodine added to hydrocarbon oils reduces friction many times over in stainless steel and titanium bearings. This allows you to increase the load on the rubbing parts whiter than 50 times.

Iodine is used to make special polaroid glass. Crystals of iodine salts are introduced into the glass, which are distributed strictly regularly. Vibrations of the light beam cannot pass through them in all directions. It turns out a kind of filter, called a polaroid, which removes the oncoming blinding stream of light. Such glass is used in automobiles. Combining several polaroids or rotating polaroid lenses, you can achieve exceptionally colorful effects - this phenomenon is used in film technology and in the theater.

Iodine - grayish-black crystals with a metallic sheen with a density of 4.93 g/cm3. It melts at 113.6° and boils at 184.4°. Heat capacity of crystals

W

0.05058+4.688 10"in/ cal/g(25- -113°), liquids 0.0756 cal/g(113.6-184°) and pair 0.0350 Cal/g(25-1200°). Melting heat 14.85 cal/g(113.6°). Heat of vaporization 56.9 cal/g Tsri 113.6° and 39.3 cal/g at 184.4°.

Vapor pressure of iodine at 25° 0.31 mmHg Art. and at 113.6° 90.5 mmHg Art. It is easily sublimated; couples are purple. When vapors condense on a cold surface, crystals form. Solubility of iodine in 1000 G water at 20° 0.28 G, 50° -0.71 g and 100° -4.5 G. In the presence of sulfates, the solubility of iodine decreases, and in the presence of

I", Br-, C1~ - increases due to the formation of complex polyhalogen ions:

R+Ij-IJ, IJ + Ij-IJ, Br-+I2 = BrI"

And so on. This greatly affects the distribution coefficient of iodine between the gas and liquid phases (Fig. 71), which is essential for

Extraction of iodine from solutions by air desorption1-4. Better than in water, iodine dissolves in ethyl alcohol, ether, chloroform, carbon disulfide, carbon tetrachloride, dichloroethane, kerosene and other organic liquids, forming colored solutions.

The dissolution of iodine in water is accompanied by hydrolysis:

70

K 30

20

Temperature^

Rns. 72. Solubility of Nal, NH4I, KI and KYUZ in water.

Go

YU

Dit in iodic acid: ZNYU = ZN+ + 2G + u; (this transition occurs more easily than similar compounds of chlorine and bromine). Therefore, the overall equation for iodine hydrolysis is:

3I2 + ZH20 = 6H+ + 5 G + IOJ

Its equilibrium constant at 20° is 6:

[N + ]6[g]5[Uz1 K ■= . s1 3J = 2.45 1(G48

With strong nitric acid, iodine is easily oxidized to 12 about at room temperature. Iodine pentoxide is highly hygroscopic and transforms into H1308 under the action of atmospheric moisture. At 280° I2Os irreversibly decomposes into 12 and 02. (After prolonged heating at 250°, a slight sublimation is observed

Leah. All these salts form colorless crystals. Sodium iodide Nal crystallizes in a cubic system with a density of 3.67 g/cm3; melts at 65° (according to other sources at 682°). Its solubility in water is shown in Fig. 72. NaI-2H20 crystallizes in a monoclinic system with a density of 2.45 g/cm3. Sodium iodide is highly hygroscopic. During long-term storage, its crystals turn yellow due to the release of free iodine. Potassium iodide KI and ammonium iodide NH4I crystallize only in the anhydrous form in the cubic system. Density KI 3.13 g/cm3, it melts at 723°; density NH4I 2.51 g/cm3. Potassium iodate KYUZ forms anhydrous crystals of the cubic system with a density of 3.89 g/cm3; melts at 560°. When heated, it decomposes with the release of oxygen. Forms acidic salt KYUZ-NUZ. Saturated aqueous solution at

15° contains 1.33% KIu8-H103.

APPLICATION

Iodine is used in medicine in the form of iodine tincture (5 and 10% solution in alcohol) or Ligol's solution (an aqueous solution of iodine containing potassium iodide) and in the form of salts and organic compounds (iodoform, iodgnost, sayodin, sergozin, iodol, etc.) .

Iodine is used in the synthesis of organic dyes, in the production of titanium, in the manufacture of certain metals of high purity (through iodides). 70-75% of iodine is processed into iodine salts, which are used, in addition to medicine, in photography, laboratory practice, in agriculture and for iodizing table salt. The world production of iodine is ~4000 t/year7-11.

According to GOST 545-71, technical iodine of the 1st and 2nd grades must contain, respectively, not less than 99 and 97.5% iodine and not more than: 0.010 and 0.015% chlorine and bromine, 0.1 and 0.2% organic substances and 0.05 and 0.15% ash. Iodine is packed in polyethylene-dacron bags placed in cardboard drums or wooden barrels.

RAW

Iodine is widely distributed in nature, but a very scattered element. Its content in the earth's crust is Liu-4 wt.%. Minerals containing iodine are rare and in very small quantities. In a diffuse state, iodine is ubiquitous. The content of iodine in rocks and minerals ranges from 1.7-10"5" to 1.2 10-4%, in natural waters from 3-10-5 to 150 mg/l And in the air 0.001-0.002 mg/m3. The air of coastal areas is richest in iodine, since in sea ​​water contains 0.01-0.04 mg/l iodides or iodates. Iodine is found in all plant and animal organisms, especially V marine (some sponges contain up to 8.5% iodine).

The raw materials for the industrial production of iodine are some natural deposits of saltpeter, seaweed and drilling water from oil and gas fields. Saltpeter-bearing rocks containing iodine are found in the northern part of South America (Chile, Bolivia, Peru). The iodine content in them ranges from 0.05 to 1%. Of the seaweed, kelp, fucus and phyllophora are especially rich in iodine. In China, these algae are grown specifically to extract iodine from them. The content of iodine in air-dry algae is 0.02-0.5%. Drilling oil fields are the main raw material for obtaining iodine in the USSR, Japan, the USA and other countries. The iodine content in them is 10-60 mg/l(in some cases up to 150 mg/l). Drilling waters used for industrial extraction of iodine have a complex salt composition, different salinity and thermal regime. It is more profitable to obtain iodine from waters rich in iodine, but all the considerations given about the extraction of bromine remain valid for the extraction of iodine (pp. 209, 216).

Iodine, along with borax and other components, can be extracted from muds containing 50-200 g/m iodine, 2.

S-NU) at x = 1. y = 1; pyrophosphoric acid HP2O (2HPOs-N0) at x = 2, y = 1. However, the transition in the series of hydrates of iodic acid occurs more easily than in the series of phosphoric acids.

In aqueous solutions, iodic acid is a markedly weaker acid than iodic acid. Its dissociation constant is 2.3-10 "g. When neutralized with methyl orange (pH "4), it gives monobasic salts, for example NaJ04-3H20; when neutralized with phenolphthalein (pHs" 8), it gives dibasic salts derived from acid HJO " -H20, such as NaeHJOs.

As an oxidizing agent, iodic acid is more active than iodic acid.

Salts of iodic acid are called periodates; they are obtained from iodic acid salts (iodates) or by anodic oxidation of alkaline solutions using platinum electrodes, or by oxidation of alkaline solutions with chlorine:

NaJOi + 3NaOH + Cli -> 2NaCl + Na.HJOs + №0.

Solubility of periodates. Alkali metal salts of iodoic acid are slightly soluble in water; the solubility of salts of alkaline earth and heavy metals is even lower. All its salts dissolve relatively easily in mineral acids, especially in nitric acid.

Wet reactions

Sodium hydroxide should be used.

1. Sulfuric acid in a dilute solution does not react.

2. Silver nitrate gives a brown precipitate Ag:, JOe, and the solution becomes acidic. The precipitate on standing, faster on heating, turns brown-black and dissolves in nitric acid (unlike iodates) and in ammonia.

3. Barium chloride precipitates a white precipitate, soluble in nitric acid.

4. Thorium nitrate does not give any precipitate (unlike iodates).

5. Mercury(2) nitrate gives off a red-brown precipitate, which does not change during boiling and is insoluble in nitric acid and ammonia.

6. Lead acetate precipitates a white lead salt of iodic acid, which is insoluble in nitric acid.

7. Iodides. In contrast to iodates, iodine salts are isolated from a neutral or even from a slightly alkaline solution of iodides, iodine:

JCV + 23" + HsO - "JOa" + J2 + 20H".

As a result of the formation of OH "-ions, the reaction of the solution becomes alkaline. With a long standing, the alkaline reaction disappears

since free iodine reacts with an excess of iodine salt

acids: 5J04" + Z2 + 20H" -> 7J03" + NIu.

In a strongly acidic solution, the interaction of iodides and leriodates proceeds quantitatively according to the equation:

JCV + 73" + 8H- -> 4J2 + 4H2O.

8. Manganese sulfate in a highly dilute acidic solution is oxidized when heated to manganese acid; in a neutral or alkaline solution, oxidation proceeds to manganese dioxide hydrate and manganese iodate.

9. Oxalic acid is rapidly oxidized to CO3 when heated, especially in the presence of manganese sulfate as a catalyst. The resulting iodide with an excess of periodate releases free iodine.

* Addition of a relaitor. 10. Copper sulfate and potassium persulfate. When heated alkaline solutions of copper salts with periodate (or tellurate) in the presence of potassium or sodium persulfate, an intense brown-red color appears. This results in the formation of a complex anion containing trivalent copper1 (p. 149). The complex compound of trivalent copper with periodates (as well as with tellurates) is so intensely colored that even in very dilute solutions one can detect iodic acid by yellow coloration. The discovery of iodic acid by this method is unambiguous in the absence of telluric acid.

Fulfillment2. A drop of copper sulfate (1:50,000), a drop of IN caustic alkali, and, finally, some solid potassium or sodium persulfate are added to a drop of the studied alkaline solution, after which it is heated to a boil. The yellow color indicates the presence of iodine (iln telluric) acid. In this way, 2 v periodate can be discovered. The limiting concentration is 1: 25,000. * A.K.

Dry reactions

yav | 1 and iodic acid is lost at approximately 30 (G sour-ro; same. They turn into iodates, which at a higher

0parauner and. K and m a, B. 40, 3362 (1907); M. V g i t i s, Rec. des chim. des Pays-Bas. 45. 429 (1925). :igl u. Uzel, Mikrochemie 19. 132 (1936).

Iodine acid"UFO*

Finding in nature. Periodic acid in the form of sodium salt is found in small quantities in Chilean saltpeter.

The free acid has a great tendency to give free hydrates. general formula(HJOtb-dl i, "HJatJTeH is the best hydrate with two molecules of M" and water W04 "2HgO, which is obtained by drying the acid over sulfuric acid. It is a prism, similar to gypsum crystals, melting at a temperature of 133 °. At a higher temperature, it decomposes with the release of water, oxygen and JzOs. characteristic feature of these hydrates is the ability to replace metals not only for acidic hydrogen, but also for water hydrogens. For example, the acid H-O*-2H30 is capable of behaving like pentaoxyic acid rN0a, giving a silver salt of the composition AgsJOe and barium Ba*(.Ob)* Some analogy in this case