Colorless gases are released when kept concentrated. USE tasks in chemistry with solutions: The relationship of various classes of inorganic substances

1. A solution of substance Y was added to a test tube with a solution of salt X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation S 2- + 2H + = H 2 S. From the proposed list, select substances X and Y that can enter into the described reaction.

1) sodium sulfide;

2) carbonic acid;

3) hydrogen chloride;

4) iron (II) sulfide;

5) potassium sulfite;

1. A solution of substance Y was added to a test tube with a solution of salt X. As a result of the reaction, a white precipitate was observed,

1) potassium nitrate;

2) barium chloride;

H) hydrochloric acid;

4) calcium carbonate;

5) sulfuric acid;

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of substance Y was added to a test tube with a solution of sodium salt X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation:

S 2- + Fe 2+ \u003d FeS.

From the proposed list, select substances X and Y that can enter into the described reaction.

1) sodium sulfide;

2) sodium sulfite;

3) hydrogen sulfide;

4) iron (II) hydroxide;

5) iron sulfate (II);

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of substance Y was added to a test tube with a solution of salt X. As a result of the reaction, evolution of a colorless gas was observed. From the proposed list, select substances X and Y that can enter into the described reaction.

1) potassium sulfite;

2) sodium hydroxide;

H) iron(II) sulfate;

4) hydrogen chloride;

5) sodium nitrate.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of acid Y was added to a test tube with a solution of substance X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: OH - + H + = H 2 O.

From the proposed list, select substances X and Y that can enter into the described reaction.

1) sodium sulfide;

2) carbonic acid;

3) sulfuric acid;

4) barium hydroxide;

5) potassium hydroxide.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of salt Y was added to a test tube with a solution of substance X. As a result of the reaction, a blue precipitate was observed. From the proposed list, select substances X and Y that can enter into the described reaction.

1) iron(II) sulfate;

2) hydrochloric acid;

3) sodium hydroxide;

4) calcium nitrate;

5) copper (II) sulfate.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of substance Y was added to a test tube with a solid, water-insoluble substance X. As a result of the reaction, the dissolution of the solid substance was observed without gas evolution. From the proposed list, select substances X and Y that can enter into the described reaction.

1) calcium carbonate;

2) sodium hydroxide;

H) barium sulfate;

4) sulfuric acid;

5) copper(II) oxide.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of salt Y was added to a test tube with a solution of substance X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: CO 3 2- + 2H + \u003d H 2 O + CO 2.

From the proposed list, select substances X and Y. that can enter into the described reaction.

1) calcium bicarbonate;

2) calcium hydroxide;

3) acetic acid;

4) sulfuric acid;

5) sodium carbonate.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of salt Y was added to a test tube with a solution of substance X. As a result of the reaction, a brown precipitate was observed. From the proposed list, select substances X and Y that can enter into the described reaction.

1) copper(II) chloride;

2) hydrochloric acid;

3) sodium hydroxide;

4) sodium nitrate;

5) iron(III) sulfate.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of substance Y was added to a test tube with an acid X solution. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: SO 3 2- + 2H + \u003d H 2 O + SO 2.

From the proposed list, select substances X and Y that can enter into the described reaction.

1) potassium sulfate;

2) hydrosulphuric acid;

3) sulfuric acid;

4) ammonium sulfide;

5) sodium sulfite.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Zinc was completely dissolved in a concentrated sodium hydroxide solution. The resulting clear solution of substance X was evaporated and then calcined. This formed a solid substance Y. From the proposed list, select substances X and Y that correspond to the description given.

1) Na 2 ZnO 2;

2) Zn(OH) 2 ;

3) ZnO;

4) Na 2;

5) NaOH.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of sodium chloride was mixed with a solution of salt X. The precipitated white precipitate was separated, the solution was evaporated, the remaining dry salt was calcined in air, and a colorless gas Y was released. From the proposed list, select substances X and Y that correspond to the description given.

1) AgNO 3 ;

2) HNO3;

3) Na 2 CO 3;

4) CO 2 ;

5) O2.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Aluminum nitrate was calcined. The resulting solid X was fused with an excess of potassium hydroxide. The resulting melt was treated with an excess of water, and a clear solution of substance Y was formed. From the proposed list, select substances X and Y that correspond to the description given.

1) Al;

2) Al 2 O 3;

3) KAlO 2 ;

4) K;

5) K 3 AlO 3 .

Write in the table the numbers of the selected substances under the corresponding letters.

1. Iron(II) hydroxide was inverted with peroxide. The resulting brown substance X was fused with solid potassium hydroxide. The resulting melt containing salt Y was treated with excess water, as a result of which the brown substance X was again obtained. From the proposed list, select substances X and Y that correspond to the above description.

1) Fe 2 O 3;

2) Fe(OH) 3 ;

3) KFeO 2 ;

4) FeO;

5) K 3 FeO 3;

Write in the table the numbers of the selected substances under the corresponding letters.

1. Aluminum hydroxide was fused with potassium hydroxide. The resulting salt X was treated with an excess of hydrochloric acid, and substance Y was formed. From the proposed list, select substances X and Y that correspond to the description given.

1) K;

2) KAlO 2 ;

3) K 3 AlO 3 ;

4) AlCl 3 ;

5) Al(ClO 4) 3;

Write in the table the numbers of the selected substances under the corresponding letters.

1. Potassium sulfite was treated with hydrochloric acid. The resulting gas X was absorbed by an excess of calcium hydroxide, and substance Y was formed. From the list provided, select substances X and Y that match the description given.

1) H2S;

2) CaS;

3) Ca(HSO 3) 2;

4) SO2;

5) CaSO3.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A strong acid X was added to one of the test tubes with a precipitate of aluminum hydroxide, and a solution of substance Y was added to the other. As a result, the precipitate was observed to dissolve in each of the test tubes. From the proposed list, select substances X and Y that can enter into the described reactions.

1) hydrobromic acid;

2) sodium hydrosulfide;

3) hydrosulfide acid;

4) potassium hydroxide;

5) ammonia hydrate.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Silver nitrate was calcined. Concentrated nitric acid was added to the formed solid residue X, and an intensive evolution of gas Y was observed. From the proposed list, select substances X and Y that correspond to the description given.

1) silver(I) oxide;

2) silver nitrite;

3) silver;

4) nitric(II) oxide;

5) nitric oxide(IV).

Write in the table the numbers of the selected substances under the corresponding letters.

Silver bromide was heated with zinc powder. The resulting salt was dissolved in water. Potassium hydroxide solution was added dropwise to the resulting solution. First, a white precipitate X occurred, and then, when a new portion of the potassium hydroxide solution was added, it completely dissolved with the formation of substance Y. From the proposed list, select substances X and Y that correspond to the above description.

1) Ag;

2) ZnBr 2 ;

3) Zn(OH) 2 ;

4) K 2 ZnO 2;

5) K2.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Phosphorus(V) chloride was added to an excess of barium hydroxide solution. The resulting precipitate X was separated, dried and calcined with sand and coal, and substance Y was formed. From the proposed list, select substances X and Y that correspond to the description given.

1) Ba 3 (PO 4) 2;

2) BaHPO4;

3) BaCl 2 ;

4) CO 2 ;

5) CO.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Sodium dichromate reacted with sodium hydroxide. The resulting substance X was treated with sulfuric acid, and an orange substance Y was isolated from the resulting solution. From the proposed list, select substances X and Y that match the description given.

1) Na 2 Cr 2 O 7;

2) Na 2 CrO 4;

3) NaCrO 2 ;

4) Na 3;

5) Na 2 SO 4.

Write in the table the numbers of the selected substances under the corresponding letters.

1. Copper(II) sulfate was added to the barium chloride solution. The resulting precipitate X was filtered off. Potassium iodide was added to the remaining solution, and a Y precipitate was observed and the color of the solution changed. From the proposed list, select substances X and Y that match the description given.

1) BaSO3;

2) BaSO4;

3) CuI 2 ;

4) CuI;

5) KCl;

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of substance Y was added to a test tube with an alkali solution (substance X). As a result, a reaction occurred that is described by the abbreviated ionic equation OH - + H + = H 2 O. From the proposed list, select substances X and Y that can enter into the described reaction.

1) potassium sulfide;

2) carbonic acid;

3) sulfuric acid;

4) barium hydroxide;

5) sodium hydroxide.

Write in the table the numbers of the selected substances under the corresponding letters.

1. As a result of the interaction of a solution of copper (II) sulfate with iron, salt X was formed. This salt was heated with concentrated sulfuric acid, as a result of which a new salt Y was formed. From the proposed list, select substances X and Y that match the description given.

1) FeS;

2) CuS;

3) FeSO 4 ;

4) FeSO 3 ;

5) Fe 2 (SO 4) 3.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A solution of sodium sulfide was added to a solution of iron(III) chloride, resulting in a precipitate. The resulting precipitate was treated with a solution of sulfuric acid, and part of the precipitate X dissolved. The undissolved part of the precipitate Y was yellow. From the proposed list, select substances X and Y that match the description given.

1) FeS;

2) Fe (OH) 2;

3) Fe 2 S 3;

4) S;

5) Fe(OH) 3 .

Write in the table the numbers of the selected substances under the corresponding letters.

1. Iron(III) chloride was added to a solution of sodium hydroxide, and precipitate X precipitated. The precipitate was separated and dissolved in hydroiodic acid. In this case, substance Y was formed. From the proposed list, select substances X and Y that correspond to the description given.

1) Fe (OH) 2;

2) Fe(OH) 3 ;

3) FeI 3 ;

4) I 2 ;

5) NaCl;

Write in the table the numbers of the selected substances under the corresponding letters.

1. An excess of carbon dioxide was passed through a solution of sodium hydroxide. Substance X thus obtained was isolated from the solution, dried and calcined. This resulted in the formation of a solid Y. From the provided list, select substances X and Y that correspond to the description given.

1) Na 2 CO 3;

2) NaHCO 3 ;

3) HCOONa;

4) Na 2 O 2;

5) Na 2 O.

Write in the table the numbers of the selected substances under the corresponding letters.

Substance X was added to one test tube with a solution of copper(II) chloride, and as a result of the reaction, the formation of a red precipitate was observed. A solution of substance Y was added to another test tube with a solution of copper(II) chloride. As a result of the reaction, an insoluble salt was formed. From the proposed list, select substances X and Y that can enter into the described reactions.

1) zinc;

2) zinc oxide;

3) potassium bromide;

4) silver fluoride;

5) silver.

Write in the table the numbers of the selected substances under the corresponding letters.

1. A few drops of salt solution X were added to one of the tubes with a solution of iron (III) sulfate, and a solution of substance Y was added to the other. As a result, a brown precipitate was observed in each of the tubes. From the proposed list, select substances X and Y that can enter into the described reactions.

1) BaCl 2 ;

2) NH3;

3) Cu(OH) 2 ;

4) K2CO3;

5) AgNO 3 ;

Write in the table the numbers of the selected substances under the corresponding letters.

1. Salt solution X was added to one of the tubes with hydrochloric acid, and substance Y was added to the other. As a result, a colorless, odorless gas was observed in each of the tubes. From the proposed list, select substances X and Y that can enter into the described reactions.

1) Copper nitrate was calcined, the resulting solid precipitate was dissolved in sulfuric acid. Hydrogen sulfide was passed through the solution, the resulting black precipitate was calcined, and the solid residue was dissolved by heating in concentrated nitric acid.

2) Calcium phosphate was fused with coal and sand, then the resulting simple substance was burned in an excess of oxygen, the combustion product was dissolved in an excess of caustic soda. A solution of barium chloride was added to the resulting solution. The resulting precipitate was treated with an excess of phosphoric acid.

Show
Ca 3 (PO 4) 2 → P → P 2 O 5 → Na 3 PO 4 → Ba 3 (PO 4) 2 → BaHPO 4 or Ba (H 2 PO 4) 2 Ca 3 (PO 4) 2 + 5C + 3SiO 2 → 3CaSiO 3 + 2P + 5CO 4P + 5O 2 → 2P 2 O 5 P 2 O 5 + 6NaOH → 2Na 3 PO 4 + 3H 2 O 2Na 3 PO 4 + 3BaCl 2 → Ba 3 (PO 4) 2 + 6NaCl Ba 3 (PO 4) 2 + 4H 3 PO 4 → 3Ba(H 2 PO 4) 2

3) Copper was dissolved in concentrated nitric acid, the resulting gas was mixed with oxygen and dissolved in water. Zinc oxide was dissolved in the resulting solution, then a large excess of sodium hydroxide solution was added to the solution.

4) Dry sodium chloride was treated with concentrated sulfuric acid at low heating, the resulting gas was passed into a solution of barium hydroxide. A solution of potassium sulfate was added to the resulting solution. The resulting precipitate was fused with coal. The resulting substance was treated with hydrochloric acid.

5) A sample of aluminum sulfide was treated with hydrochloric acid. In this case, gas was released and a colorless solution was formed. An ammonia solution was added to the resulting solution, and the gas was passed through a solution of lead nitrate. The precipitate thus obtained was treated with a solution of hydrogen peroxide.

Show
Al(OH) 3 ←AlCl 3 ←Al 2 S 3 → H 2 S → PbS → PbSO 4 Al 2 S 3 + 6HCl → 3H 2 S + 2AlCl 3 AlCl 3 + 3NH 3 + 3H 2 O → Al(OH) 3 + 3NH 4 Cl H 2 S + Pb(NO 3) 2 → PbS + 2HNO 3 PbS + 4H 2 O 2 → PbSO 4 + 4H 2 O

6) Aluminum powder was mixed with sulfur powder, the mixture was heated, the resulting substance was treated with water, gas was released and a precipitate formed, to which an excess of potassium hydroxide solution was added until complete dissolution. This solution was evaporated and calcined. An excess of hydrochloric acid solution was added to the resulting solid.

7) A solution of potassium iodide was treated with a solution of chlorine. The resulting precipitate was treated with sodium sulfite solution. First, a solution of barium chloride was added to the resulting solution, and after separating the precipitate, a solution of silver nitrate was added.

8) A gray-green powder of chromium (III) oxide was fused with an excess of alkali, the resulting substance was dissolved in water, and a dark green solution was obtained. Hydrogen peroxide was added to the resulting alkaline solution. A yellow solution was obtained, which turns orange when sulfuric acid is added. When hydrogen sulfide is passed through the resulting acidified orange solution, it becomes cloudy and turns green again.

Show
Cr 2 O 3 → KCrO 2 → K → K 2 CrO 4 → K 2 Cr 2 O 7 → Cr 2 (SO 4) 3 Cr 2 O 3 + 2KOH → 2KCrO 2 + H 2 O 2KCrO 2 + 3H 2 O 2 + 2KOH → 2K 2 CrO 4 + 4H 2 O 2K 2 CrO 4 + H 2 SO 4 → K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O K 2 Cr 2 O 7 + 3H 2 S + 4H 2 SO 4 → 3S + Cr 2 (SO 4) 3 + K 2 SO 4 + 7H 2 O

9) Aluminum was dissolved in a concentrated solution of potassium hydroxide. Carbon dioxide was passed through the resulting solution until the precipitation ceased. The precipitate was filtered off and calcined. The resulting solid residue was fused with sodium carbonate.

10) Silicon was dissolved in a concentrated solution of potassium hydroxide. An excess of hydrochloric acid was added to the resulting solution. The cloudy solution was heated. The separated precipitate was filtered off and calcined with calcium carbonate. Write the equations of the described reactions.

11) Copper(II) oxide was heated in a stream of carbon monoxide. The resulting substance was burned in an atmosphere of chlorine. The reaction product was dissolved in water. The resulting solution was divided into two parts. A solution of potassium iodide was added to one part, a solution of silver nitrate was added to the second. In both cases, the formation of a precipitate was observed. Write the equations for the four described reactions.

12) Copper nitrate was calcined, the resulting solid was dissolved in dilute sulfuric acid. The resulting salt solution was subjected to electrolysis. The substance released at the cathode was dissolved in concentrated nitric acid. The dissolution proceeded with evolution of brown gas. Write the equations for the four described reactions.

13) Iron was burned in an atmosphere of chlorine. The resulting material was treated with an excess of sodium hydroxide solution. A brown precipitate formed, which was filtered off and calcined. The residue after calcination was dissolved in hydroiodic acid. Write the equations for the four described reactions.
14) Powder of metallic aluminum was mixed with solid iodine and a few drops of water were added. Sodium hydroxide solution was added to the resulting salt until a precipitate formed. The resulting precipitate was dissolved in hydrochloric acid. Upon subsequent addition of sodium carbonate solution, precipitation was again observed. Write the equations for the four described reactions.

15) As a result of incomplete combustion of coal, a gas was obtained, in the flow of which iron oxide (III) was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting salt solution was subjected to electrolysis. Write the equations for the four described reactions.

16) Some amount of zinc sulfide was divided into two parts. One of them was treated with nitric acid, and the other was fired in air. During the interaction of the evolved gases, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released. Write the equations for the four described reactions.

17) Potassium chlorate was heated in the presence of a catalyst, and a colorless gas was released. By burning iron in an atmosphere of this gas, iron scale was obtained. It was dissolved in an excess of hydrochloric acid. To the solution thus obtained was added a solution containing sodium dichromate and hydrochloric acid.

Show

1) 2KClO 3 → 2KCl + 3O 2 2) ЗFe + 2O 2 → Fe 3 O 4 3) Fe 3 O 4 + 8HCI → FeCl 2 + 2FeCl 3 + 4H 2 O 4) 6 FeCl 2 + Na 2 Cr 2 O 7 + 14 HCI → 6 FeCl 3 + 2 CrCl 3 + 2NaCl + 7H 2 O 18) Iron burned in chlorine. The resulting salt was added to a solution of sodium carbonate, and a brown precipitate fell out. This precipitate was filtered off and calcined. The resulting substance was dissolved in hydroiodic acid. Write the equations for the four described reactions. 1) 2Fe + 3Cl 2 → 2FeCl 3 2) 2FeCl 3 + 3Na 2 CO 3 → 2Fe (OH) 3 + 6NaCl + 3CO 2 3) 2Fe(OH) 3 Fe 2 O 3 + 3H 2 O 4) Fe 2 O 3 + 6HI → 2FeI 2 + I 2 + 3H 2 O

19) A solution of potassium iodide was treated with an excess of chlorine water, while observing first the formation of a precipitate, and then its complete dissolution. The iodine-containing acid thus formed was isolated from the solution, dried, and gently heated. The resulting oxide reacted with carbon monoxide. Write down the equations of the described reactions.

20) Chromium(III) sulfide powder was dissolved in sulfuric acid. In this case, gas was released and a colored solution was formed. An excess of ammonia solution was added to the resulting solution, and the gas was passed through lead nitrate. The resulting black precipitate turned white after treatment with hydrogen peroxide. Write down the equations of the described reactions.

21) Aluminum powder was heated with sulfur powder, the resulting substance was treated with water. The resulting precipitate was treated with an excess of concentrated potassium hydroxide solution until it was completely dissolved. A solution of aluminum chloride was added to the resulting solution, and the formation of a white precipitate was again observed. Write down the equations of the described reactions.

22) Potassium nitrate was heated with powdered lead until the reaction ceased. The mixture of products was treated with water, and then the resulting solution was filtered. The filtrate was acidified with sulfuric acid and treated with potassium iodide. The released simple substance was heated with concentrated nitric acid. In the atmosphere of the resulting brown gas, red phosphorus was burned. Write down the equations of the described reactions.

23) Copper was dissolved in dilute nitric acid. An excess of ammonia solution was added to the resulting solution, observing first the formation of a precipitate, and then its complete dissolution with the formation of a dark blue solution. The resulting solution was treated with sulfuric acid until the characteristic blue color of copper salts appeared. Write down the equations of the described reactions.

Show
1) 3Cu + 8HNO 3 → 3Cu (NO 3) 2 + 2NO + 4H 2 O 2) Cu (NO 3) 2 + 2NH 3 H 2 O → Cu (OH) 2 + 2NH 4 NO 3 3) Cu (OH) 2 + 4NH 3 H 2 O → (OH) 2 + 4H 2 O 4) (OH) 2 + 3H 2 SO 4 → CuSO 4 + 2 (NH 4) 2 SO 4 + 2H 2 O

24) Magnesium was dissolved in dilute nitric acid, and no evolution of gas was observed. The resulting solution was treated with an excess of potassium hydroxide solution while heating. The resulting gas was burned in oxygen. Write down the equations of the described reactions.
25) A mixture of potassium nitrite and ammonium chloride powders was dissolved in water and the solution heated gently. The released gas reacted with magnesium. The reaction product was added to an excess of hydrochloric acid solution, and no gas evolution was observed. The resulting magnesium salt in solution was treated with sodium carbonate. Write down the equations of the described reactions.

26) Aluminum oxide was fused with sodium hydroxide. The reaction product was added to an ammonium chloride solution. The released gas with a pungent odor is absorbed by sulfuric acid. The middle salt thus formed was calcined. Write down the equations of the described reactions.

27) Chlorine reacted with a hot solution of potassium hydroxide. When the solution was cooled, crystals of Berthollet salt precipitated. The resulting crystals were added to a hydrochloric acid solution. The resulting simple substance reacted with metallic iron. The reaction product was heated with a new sample of iron. Write down the equations of the described reactions.
28) Copper was dissolved in concentrated nitric acid. An excess of ammonia solution was added to the resulting solution, observing first the formation of a precipitate, and then its complete dissolution. The resulting solution was treated with an excess of hydrochloric acid. Write down the equations of the described reactions.

29) Iron was dissolved in hot concentrated sulfuric acid. The resulting salt 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 for the four described reactions.

30) As a result of incomplete combustion of coal, a gas was obtained, in the flow of which iron oxide (III) was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting salt solution was treated with an excess of potassium sulfide solution.

31) Some amount of zinc sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. During the interaction of the evolved gases, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released.

32) Sulfur was fused with iron. The reaction product was treated with hydrochloric acid. The resulting gas was burned in an excess of oxygen. The combustion products were absorbed by an aqueous solution of iron(III) sulfate.

Formation of a gaseous substance

Na 2 S + 2HCl \u003d H 2 S + 2NaCl

2Na + + S 2- + 2H + + 2Cl - \u003d H 2 S + 2Na + + 2Cl -

Ionic-molecular reaction equation,

2H + + S 2- = H 2 S is a short form of the reaction equation.

1. Precipitation formation

with the formation of poorly soluble substances:

a) NaCl + AgNO 3 = NaNO 3 + AgCl

Cl - + Ag + = AgCl - reduced ion-molecular equation.

Reactions in which weak electrolytes or poorly soluble substances are included in the composition of both products and initial substances, as a rule, do not proceed to the end, i.e. are reversible. The equilibrium of the reversible process in these cases is shifted towards the formation of the least dissociated or least soluble particles..

BaCl 2 + Na 2 SO 4 = BaSO 4 ↓ + 2NaCl

Molecular reaction equation,

Ba 2+ + 2Cl - + 2Na + + SO= BaSO 4 ↓ + 2Na + + 2Cl -

Ionic-molecular reaction equation,

Ba 2+ + SO \u003d BaSO 4 ↓ - a short form of the reaction equation.

1. Precipitation condition. Solubility product

There are no absolutely insoluble substances. Most solids have limited solubility. In saturated electrolyte solutions of sparingly soluble substances, the precipitate and the saturated electrolyte solution are in a state of dynamic equilibrium. For example, in a saturated solution of barium sulfate, which is in contact with the crystals of this substance, a dynamic equilibrium is established:

BaSO 4 (t) \u003d Ba 2+ (p) + SO 4 2- (p).

For this equilibrium process, we can write the expression for the equilibrium constant, taking into account that the concentration of the solid phase is not included in the expression for the equilibrium constant: Kp =

This value is called the solubility product of a sparingly soluble substance (PR). Thus, in a saturated solution of a poorly soluble compound, the product of the concentrations of its ions to the power of stoichiometric coefficients is equal to the value of the solubility product. In the considered example

PR BaSO4 = .

The solubility product characterizes the solubility of a poorly soluble substance at a given temperature: the smaller the solubility product, the worse the solubility of the compound. Knowing the solubility product, one can determine the solubility of a sparingly soluble electrolyte and its content in a certain volume of a saturated solution.

In a saturated solution of a strong, sparingly soluble electrolyte, the product of the concentrations of its ions in powers equal to the stoichiometric coefficients for given ions (at a given temperature) is a constant value, called the solubility product.

The value of PR characterizes the comparative solubility of substances of the same type (forming the same number of ions during dissociation) substances. The greater the PR of a given substance, the greater its solubility. For example:

In this case, the least soluble is iron (II) hydroxide.

Precipitation condition :

X y > PR(K x A y).

This condition is achieved by introducing the ion of the same name into the saturated solution-precipitate system. Such a solution is supersaturated relative to this electrolyte, so it will precipitate.

Precipitate dissolution condition:

X y< ПР(K x A y).

This condition is achieved by binding one of the ions sent by the precipitate into the solution. The solution in this case is unsaturated. When crystals of a sparingly soluble electrolyte are introduced into it, they will dissolve. The equilibrium molar concentrations of K y+ and A x- ions are proportional to the solubility S (mol/l) of the substance K x A y:

X S and = y S

PR = (x S) x (y S) y = x x y y S x+y

The relations obtained above make it possible to calculate the values ​​of SP from the known solubility of substances (and, consequently, the equilibrium concentrations of ions) from the known values ​​of SP at T = const.

• Tasks for self-examination are a prerequisite for mastering the material, each section is accompanied by test tasks on the topics covered, which must be solved.
• Having solved all the tasks from the section, you will see your result and be able to see the answers to all the examples, which will help you understand what mistakes you made and where your knowledge needs to be strengthened!
• The test consists of 10 tests of task 8, part 1 of the USE, the answers are mixed randomly, and are taken from the database of questions we created!
• Try to get above 90% correct answers to be sure of your knowledge!

If you are studying with a tutor, then write your real name at the beginning of testing! Based on your name, the tutor will find the test you passed, review your mistakes and take into account your gaps in order to fill them in the future!

• Use only the reference material below if you want to check the fixing of the material!
• After passing the test, look at the answers to the questions where you made a mistake and consolidate the material before re-passing!

Reference material for passing the test:

periodic table

Solubility table

The types of questions that are found in this test (you can see the answers to the questions and the full conditions of the tasks by passing the test above to the end. We advise you to look at how to solve these questions in ours):

• A solution of substance Y was added to a test tube with a solution of salt X. As a result, a reaction occurred, which is described by the abbreviated ionic equation ____. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of substance Y was added to a test tube with a solution of salt X. As a result of the reaction, a white precipitate was observed. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of substance Y was added to a test tube with a solution of potassium salt X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: ____. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of substance Y was added to a test tube with a solution of salt X. As a result of the reaction, evolution of a colorless gas was observed. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of acid Y was added to a test tube with a solution of substance X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: ____. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of salt Y was added to a test tube with a solution of substance X. As a result of the reaction, a blue precipitate was observed. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of substance Y was added to a test tube with a solid, water-insoluble substance X. As a result of the reaction, the dissolution of the solid substance was observed without gas evolution. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of salt Y was added to a test tube with a solution of substance X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation: ____. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of salt Y was added to a test tube with a solution of substance X. As a result of the reaction, a brown precipitate was observed. From the proposed list, select substances X and Y that can enter into the described reaction.
• A solution of substance Y was added to a test tube with a solution of acid X. As a result, a reaction occurred, which is described by the following abbreviated ionic equation. From the proposed list, select substances X and Y that can enter into the described reaction.

Let's imagine the following situation:

You work in a lab and decide to do an experiment. To do this, you opened the cabinet with reagents and suddenly saw the following picture on one of the shelves. Two jars of reagents had their labels peeled off, which were safely left lying nearby. At the same time, it is no longer possible to determine exactly which jar corresponds to which label, and the external signs of the substances by which they could be distinguished are the same.

In this case, the problem can be solved using the so-called qualitative reactions.

Qualitative reactions called such reactions that allow you to distinguish one substance from another, as well as to find out the qualitative composition of unknown substances.

For example, it is known that the cations of some metals, when their salts are added to the burner flame, color it in a certain color:

This method can only work if the substances to be distinguished change the color of the flame in different ways, or one of them does not change color at all.

But, let's say, as luck would have it, the substances you determine do not color the color of the flame, or they color it in the same color.

In these cases, it will be necessary to distinguish substances using other reagents.

In what case can we distinguish one substance from another with the help of any reagent?

There are two options:

• One substance reacts with the added reagent, while the other does not. At the same time, it must be clearly seen that the reaction of one of the starting substances with the added reagent has really passed, that is, some external sign of it is observed - a precipitate precipitated, gas was released, a color change occurred, etc.

For example, it is impossible to distinguish water from a sodium hydroxide solution using hydrochloric acid, despite the fact that alkalis react perfectly with acids:

NaOH + HCl \u003d NaCl + H 2 O

This is due to the absence of any external signs of a reaction. A transparent colorless solution of hydrochloric acid, when mixed with a colorless hydroxide solution, forms the same transparent solution:

But on the other hand, water can be distinguished from an aqueous solution of alkali, for example, using a solution of magnesium chloride - a white precipitate forms in this reaction:

2NaOH + MgCl 2 = Mg(OH) 2 ↓+ 2NaCl

2) substances can also be distinguished from each other if they both react with the added reagent, but do so in different ways.

For example, a solution of sodium carbonate can be distinguished from a solution of silver nitrate using a solution of hydrochloric acid.

hydrochloric acid reacts with sodium carbonate to release a colorless, odorless gas - carbon dioxide (CO 2):

2HCl + Na 2 CO 3 \u003d 2NaCl + H 2 O + CO 2

and with silver nitrate to form a white cheesy precipitate AgCl

HCl + AgNO 3 \u003d HNO 3 + AgCl ↓

The tables below show different options for detecting specific ions:

Qualitative reactions to cations

Cation	Reagent	Sign of reaction
Ba 2+	SO 4 2-	Ba 2+ + SO 4 2- \u003d BaSO 4 ↓
Cu2+		1) Precipitation of blue color: Cu 2+ + 2OH - \u003d Cu (OH) 2 ↓ 2) Precipitation of black color: Cu 2+ + S 2- \u003d CuS ↓
Pb 2+	S2-	Precipitation of black color: Pb 2+ + S 2- = PbS↓
Ag+	Cl-	Precipitation of a white precipitate, insoluble in HNO 3, but soluble in ammonia NH 3 H 2 O: Ag + + Cl − → AgCl↓
Fe2+	2) Potassium hexacyanoferrate (III) (red blood salt) K 3	1) Precipitation of a white precipitate that turns green in air: Fe 2+ + 2OH - \u003d Fe (OH) 2 ↓ 2) Precipitation of a blue precipitate (turnbull blue): K + + Fe 2+ + 3- = KFe↓
Fe3+	2) Potassium hexacyanoferrate (II) (yellow blood salt) K 4 3) Rhodanide ion SCN −	1) Precipitation of brown color: Fe 3+ + 3OH - \u003d Fe (OH) 3 ↓ 2) Precipitation of a blue precipitate (Prussian blue): K + + Fe 3+ + 4- = KFe↓ 3) The appearance of intense red (blood red) staining: Fe 3+ + 3SCN - = Fe(SCN) 3
Al 3+	Alkali (hydroxide amphoteric properties)	Precipitation of a white precipitate of aluminum hydroxide when a small amount of alkali is added: OH - + Al 3+ \u003d Al (OH) 3 and its dissolution upon further addition: Al(OH) 3 + NaOH = Na
NH4+	OH − , heating	Emission of gas with a pungent odor: NH 4 + + OH - \u003d NH 3 + H 2 O Blue wet litmus paper
H+ (acid environment)	Indicators: − litmus − methyl orange	Red staining

Qualitative reactions to anions

Anion	Impact or reagent	Reaction sign. Reaction equation
SO 4 2-	Ba 2+	Precipitation of a white precipitate, insoluble in acids: Ba 2+ + SO 4 2- \u003d BaSO 4 ↓
NO 3 -	1) Add H 2 SO 4 (conc.) and Cu, heat 2) A mixture of H 2 SO 4 + FeSO 4	1) Formation of a blue solution containing Cu 2+ ions, brown gas evolution (NO 2) 2) The appearance of the color of nitroso-iron sulfate (II) 2+. Violet to brown color (brown ring reaction)
PO 4 3-	Ag+	Precipitation of a light yellow precipitate in a neutral medium: 3Ag + + PO 4 3- = Ag 3 PO 4 ↓
CrO 4 2-	Ba 2+	Precipitation of a yellow precipitate, insoluble in acetic acid, but soluble in HCl: Ba 2+ + CrO 4 2- = BaCrO 4 ↓
S2-	Pb 2+	Black precipitation: Pb 2+ + S 2- = PbS↓
CO 3 2-		1) Precipitation of a white precipitate, soluble in acids: Ca 2+ + CO 3 2- \u003d CaCO 3 ↓ 2) Emission of a colorless gas ("boiling"), causing the lime water to become cloudy: CO 3 2- + 2H + = CO 2 + H 2 O
CO2	Lime water Ca(OH) 2	Precipitation of a white precipitate and its dissolution upon further passage of CO 2: Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 O CaCO 3 + CO 2 + H 2 O \u003d Ca (HCO 3) 2
SO 3 2-	H+	SO 2 gas evolution with a characteristic pungent odor (SO 2): 2H + + SO 3 2- \u003d H 2 O + SO 2
F-	Ca2+	Precipitation of a white precipitate: Ca 2+ + 2F - = CaF 2 ↓
Cl-	Ag+	Precipitation of a white cheesy precipitate, insoluble in HNO 3 but soluble in NH 3 H 2 O (conc.): Ag + + Cl - = AgCl↓ AgCl + 2(NH 3 H 2 O) =) We also recommend Hero pioneers in the Great Patriotic War Heroes of the Patriotic War pioneers presentation Presentation "Formation of posture in preschool children Hygiene of correct posture presentation for children Sciences of the human body Presentation "history and prospects for the development of robotics" The value of the struggle of Russia with the Polovtsy Asia and Africa after World War II Loading...