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 fired, 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 excess oxygen, the combustion product was dissolved in excess caustic soda. A barium chloride solution was added to the resulting solution. The resulting precipitate was treated with excess phosphoric acid.
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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 |
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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 with 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 sediment was fused with coal. The resulting substance was treated with hydrochloric acid.
5) A sample of aluminum sulfide was treated with hydrochloric acid. At the same time, 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 lead nitrate solution. The resulting precipitate was treated with a solution of hydrogen peroxide.
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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 |
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6) Aluminum powder was mixed with sulfur powder, the mixture was heated, the resulting substance was treated with water, a gas was released and a precipitate was 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 a solution of sodium sulfite. A solution of barium chloride was first added to the resulting solution, and after separation of the precipitate, a solution of silver nitrate was added.
8) Gray-green powder of chromium (III) oxide was fused with an excess of alkali, the resulting substance was dissolved in water, resulting in a dark green solution. Hydrogen peroxide was added to the resulting alkaline solution. The result is a yellow solution, 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.
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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 |
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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 and calcined. The resulting solid residue was fused with sodium carbonate.
10) Silicon was dissolved in a concentrated solution of potassium hydroxide. Excess hydrochloric acid was added to the resulting solution. The cloudy solution was heated. The resulting precipitate was filtered and calcined with calcium carbonate. Write the equations for the reactions described.
11) Copper(II) oxide was heated in a stream of carbon monoxide. The resulting substance was burned in a chlorine atmosphere. 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, and a solution of silver nitrate was added to the second. In both cases, the formation of a precipitate was observed. Write equations for the four reactions described.
12) Copper nitrate was calcined, the resulting solid was dissolved in dilute sulfuric acid. The solution of the resulting salt was subjected to electrolysis. The substance released at the cathode was dissolved in concentrated nitric acid. Dissolution proceeded with the release of brown gas. Write equations for the four reactions described.
13) Iron was burned in a chlorine atmosphere. The resulting substance was treated with an excess of sodium hydroxide solution. A brown precipitate formed, which was filtered and calcined. The residue after calcination was dissolved in hydroiodic acid. Write equations for the four reactions described.
14) Aluminum metal powder was mixed with solid iodine and a few drops of water were added. A solution of sodium hydroxide 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 equations for the four reactions described.
15) As a result of incomplete combustion of coal, a gas was obtained, in the current of which iron(III) oxide was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting salt solution was subjected to electrolysis. Write equations for the four reactions described.
16) A certain amount of zinc sulfide was divided into two parts. One of them was treated with nitric acid, and the other was fired in air. When the released gases interacted, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released. Write equations for the four reactions described.
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 oxide was obtained. It was dissolved in excess hydrochloric acid. To the resulting solution was added a solution containing sodium dichromate and hydrochloric acid.
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1) 2KClO 3 → 2KCl + 3O 2 2) ЗFe + 2O 2 → Fe 3 O 4 3) Fe 3 O 4 + 8НІ → 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 was burned in chlorine. The resulting salt was added to the sodium carbonate solution, and a brown precipitate formed. This precipitate was filtered and calcined. The resulting substance was dissolved in hydroiodic acid. Write equations for the four reactions described. 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 |
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19) A solution of potassium iodide was treated with an excess of chlorine water, and first the formation of a precipitate was observed, and then its complete dissolution. The resulting iodine-containing acid was isolated from the solution, dried and carefully heated. The resulting oxide reacted with carbon monoxide. Write down the equations for the reactions described.
20) Chromium(III) sulfide powder was dissolved in sulfuric acid. At the same time, 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 for the reactions described.
21) Aluminum powder was heated with sulfur powder, and the resulting substance was treated with water. The resulting precipitate was treated with an excess of a concentrated solution of potassium hydroxide 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 for the reactions described.
22) Potassium nitrate was heated with powdered lead until the reaction stopped. 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 isolated simple substance was heated with concentrated nitric acid. Red phosphorus was burned in the atmosphere of the resulting brown gas. Write down the equations for the reactions described.
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 for the reactions described.
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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 |
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24) Magnesium was dissolved in dilute nitric acid, and no gas evolution was observed. The resulting solution was treated with an excess of potassium hydroxide solution while heating. The gas released was burned in oxygen. Write down the equations for the reactions described.
25) A mixture of potassium nitrite and ammonium chloride powders was dissolved in water and the solution was gently heated. 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 for the reactions described.
26) Aluminum oxide was fused with sodium hydroxide. The reaction product was added to a solution of ammonium chloride. The released gas with a pungent odor is absorbed by sulfuric acid. The resulting medium salt was calcined. Write down the equations for the reactions described.
27) Chlorine reacted with a hot solution of potassium hydroxide. As the solution cooled, crystals of Berthollet salt precipitated. The resulting crystals were added to a solution of hydrochloric acid. The resulting simple substance reacted with metallic iron. The reaction product was heated with a new portion of iron. Write down the equations for the reactions described.
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 excess hydrochloric acid. Write down the equations for the reactions described.
29) Iron was dissolved in hot concentrated sulfuric acid. The resulting salt was treated with an excess of sodium hydroxide solution. The brown precipitate that formed was filtered and calcined. The resulting substance was fused with iron. Write equations for the four reactions described.
30) As a result of incomplete combustion of coal, a gas was obtained, in the current of which iron(III) oxide 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) A certain amount of zinc sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. When the released gases interacted, 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 gas released was burned in excess oxygen. The combustion products were absorbed by an aqueous solution of iron(III) sulfate.
Description of the presentation by individual slides:
1 slide
Slide description:
TASKS FOR PREPARATION FOR THE Unified State Exam Prepared by: Sviridova N.A., teacher of the MKOU Bolshevereyskaya Secondary School
2 slide
Slide description:
A simple substance obtained by heating calcium phosphate with coke and silicon oxide was fused with calcium metal. The reaction product was treated with water, and the released gas was collected and passed through a solution of hydrochloric acid. Write the equations for the reactions described. Ca3(PO4)2 + 5C + 3SiO2 → 3CaSiO3 + 2P + 5CO 2P + 3Ca → Ca3P2 Ca3P2 + 6H2O → 3Ca(OH)2 + 2PH3 PH3 + HCl → PH4Cl
3 slide
Slide description:
The 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. Sodium nitrate and hydroxide were added to the remaining substance and heated at high temperature for a long time. Write the equations for the reactions described. FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl 2Fe(OH)3 → Fe2O3 + 3H2O Fe2O3 + Na2CO3 → 2NaFeO2 + CO2 2NaFeO2 + 3NaNO3 + 2NaOH → 2Na2FeO4 + 3NaNO2 + H2O
4 slide
Slide description:
Concentrated hydrochloric acid was added to lead(IV) oxide while heating. The released gas was passed through a heated solution of caustic potassium. The oxygen-containing acid salt, which precipitated when the solution was cooled, was filtered and dried. When the resulting salt is heated with hydrochloric acid, a poisonous gas is released, and when it is heated in the presence of manganese dioxide, a gas that is part of the atmosphere is released. Write the equations for the reactions described. PbO2 + 4HCl → Cl2 + PbCl2 + 2H2O 3Cl2 + 6KOH → 5KCl + KClO3 + 3H2O KClO3 + 6HCl → 3Cl2 + KCl + 3H2O 2KClO3 → 2KCl + 3O2
5 slide
Slide description:
Excess sodium hydroxide solution was added to the aluminum sulfate solution. Hydrochloric acid was added to the resulting solution in small portions, and the formation of a voluminous 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 for the reactions described. Al2(SO4)3 + 8NaOH → 2Na + 3Na2SO4 2Na + 3HCl → Al(OH)3 + 3NaCl + 3H2O Al(OH)3 + 3HCl → AlCl3 + 3H2O 2 AlCl3 + 3H2O + 3Na2CO3 → 2 Al(OH)3 + 6NaCl + 3CO2
6 slide
Slide description:
After briefly heating an unknown orange powdery substance, 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 potassium hydroxide and heated, the resulting substance was added to a dilute solution of hydrochloric acid, and a green precipitate was formed, which dissolved in the excess acid. Write the equations for the reactions described. (NH4)2Cr2O7 → N2 + Cr2O3 + 4H2O Cr2O3 + 2KOH → 2KCrO2 + H2O KCrO2 + H2O + HCl → KCl + Cr(OH)3 Cr(OH)3 + 3HCl → CrCl3 + 4H2O
7 slide
Slide description:
Nitric acid was neutralized with baking soda, the neutral solution was carefully evaporated and the residue was calcined. The resulting substance was added to a solution of potassium permanganate acidified with sulfuric acid, and the solution became colorless. The nitrogen-containing reaction product was placed in a solution of caustic soda and zinc dust was added, and a gas with a sharp characteristic odor was released. Write the equations for the reactions described. HNO3 + NaHCO3 → NaNO3 + H2O + CO2 2NaNO3 → 2NaNO2 + O2 5NaNO2 + 2KMnO4 + 3H2SO4 → 5NaNO3 + K2SO4 + 2MnSO4 + 3H2O NaNO3 + 4Zn + 7NaOH + 6H2O → NH3 + 4Na2
8 slide
Slide description:
The substance obtained at the cathode during the electrolysis of molten sodium chloride was burned in oxygen. The resulting product was successively treated with sulfur dioxide and a barium hydroxide solution. Write the equations for the reactions described. 2NaCl(melt) → 2Na + Cl2 (electrolysis) 2Na + O2 → Na2O2 Na2O2 + SO2 → Na2SO4 Na2SO4 + Ba(OH)2 → BaSO4 + 2NaOH
Slide 9
Slide description:
Copper wire was introduced into heated concentrated sulfuric acid, and the released gas was passed through an excess of caustic soda 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, and the formation of a precipitate and the release of a gas with a pungent odor were observed. Write the equations for the reactions described. 2H2SO4(conc) + Cu → CuSO4 + SO2 + 2H2O 2NaOH + SO2 → Na2SO3 + H2O Na2SO3 + S → Na2S2O3 Na2S2O3 + H2SO4 → Na2SO4 + SO2 + S + H2O
10 slide
Slide description:
The substance formed when magnesium fuses with silicon was treated with water, resulting in the formation of a precipitate and the release of a colorless gas. The precipitate was dissolved in hydrochloric acid, and the gas was passed through a solution of potassium permanganate, which resulted in the formation of two water-insoluble binary substances. Write the equations for the reactions described. 2Mg + Si → Mg2Si Mg2Si + 4H2O → 2Mg(OH)2 + SiH4 Mg(OH)2 + 2HCl → MgCl2 + 2H2O 3SiH4 + 8KMnO4 → 8MnO2 + 3SiO2 + 8KOH + 2H2O
11 slide
Slide description:
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 equations for the reactions described. ZnO + H2SO4 → ZnSO4 + H2O 2ZnSO4 → 2ZnO + 2SO2 + O2 ZnO + 2NaOH + H2O → Na2 Na2 + CO2 → Na2CO3 + Zn(OH)2 + H2O
12 slide
Slide description:
Phosphine was passed through a hot solution of concentrated nitric acid. The reaction products were 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 solution of sodium hydroxide. Write the equations for the reactions described. PH3 + 8HNO3(conc) → H3PO4 + 8NO2 + 4H2O H3PO4 + 3CaO → Ca3(PO4)2 + 3H2O Ca3(PO4)2 + 3SiO2 + 5C → 3CaSiO3 + 5CO + 2P P4 + 3NaOH + 3H2O → 3NaH2PO2 + PH 3
Slide 13
Slide description:
The substance obtained at the anode by electrolysis of a sodium iodide solution on inert electrodes was reacted with potassium. The reaction product was heated with concentrated sulfuric acid, and the resulting gas was passed through a hot solution of potassium chromate. Write the equations for the reactions described. 2NaI + 2H2O → 2NaOH + H2 + I2 (electrolysis) I2 + 2K → 2KI 8KI + 5H2SO4(conc) → 4I2 + H2S + 4K2SO4 + 4H2O 3H2S + 2K2Cr2O4 + 2H2O → 2Cr(OH)3 + 3S + 4KOH
Slide 14
Slide description:
Two salts turn the flame purple. One of them is colorless, and when it is slightly heated with concentrated sulfuric acid, the liquid in which copper dissolves is distilled off; the latter transformation is accompanied by the release of brown gas. When a second salt of a 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 for the reactions described. KNO3(s) + H2SO4(conc) → KHSO4 + HNO3 Cu + 4HNO3(conc) → Cu(NO3)2 + 2NO2 + 2H2O 2K2CrO4 + H2SO4 → K2Cr2O7 + K2SO4 + H2O K2Cr2O7 +2KOH → 2K2CrO4 + H2O
16 slide
Slide description:
The substance obtained at the cathode by electrolysis of sodium chloride with inert electrodes reacts with iodine when heated. The reaction product reacts with concentrated sulfuric acid to release a gas, which is passed through a solution of potassium hydroxide. Write the equations for the reactions described. 2NaCl + 2H2O → 2NaOH + H2 + Cl2 (electrolysis) H2 + I2 → 2HI 2HI + H2SO4(conc) → I2 + SO2 + 2H2O or 8HI + H2SO4(conc) → 4I2 + H2S + 4H2O SO2 + 2KOH → K2SO3 + H2O or H2S + 2KOH → K2S + 2H2O
Slide 17
Slide description:
The salt obtained by dissolving iron in hot concentrated sulfuric acid was treated with an excess of sodium hydroxide solution. The brown precipitate that formed was filtered and calcined. The resulting substance was fused with iron. Write the equations for the reactions described. 2Fe + 6H2SO4(conc) → Fe2(SO4)3 + 3SO2 + 6H2O Fe2(SO4)3 + NaOH → 2Fe(OH)3 + 3Na2SO4 2Fe(OH)3 → Fe2O3 + 3H2O Fe2O3 + Fe → 2FeO
From the rehearsal test options (V.N. Doronkin “Preparation for the Unified State Exam – 2012”)
1. The solution obtained by reacting 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 for the reactions described.
C getting the answer
1) Cu+4HNO 3(conc) →Cu(NO 3) 2 +2NO 2 +2H 2 O
2) 2 Cu(NO 3) 2 → 2CuO +4NO 2 +O 2
3) CuO + H 2 → Cu + H 2 O
4) 4NO 2 +2H 2 O+O 2 →4HNO 3
2. A simple substance obtained by heating calcium phosphate with coke and silicon oxide was fused with calcium metal. The reaction product was treated with water, and the released gas was collected and passed through a solution of hydrochloric acid. Write the equations for the reactions described.
C getting the answer
1) Ca 3 (PO 4) 2 ↓+5C+3SiO 2 → 3CaSiO 3 +2P+ 5CO
2) 2Р+3Са→Са 3 Р 2
3) Ca 3 P 2 +6H 2 O → 3Ca(OH) 2 +2PH 3
4) RN 3 +HC1→RN 4 C1
3) The 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. Sodium nitrate and hydroxide were added to the remaining substance and heated at high temperature for a long time.
Write the equations for the reactions described.
C getting the answer
1) FeС1 3 +3NаОН→Fe(ОН) 3 ↓+3NаС1
2) 2Fe(OH) 3 → Fe 2 O 3 ↓+3H 2 O
3) Fe 2 O 3 + Na 2 CO 3 → 2NaFeO 2 + CO 2
4) 2NaFeO 2 +3NaNO 3 +2NaOH → 2Na 2 FeO 4 +2NaNO 2 + H 2 O
4) Concentrated hydrochloric acid was added to lead(IV) oxide while heating. The released gas was passed through a heated solution of caustic potassium. The oxygen-containing acid salt, which precipitated when the solution was cooled, was filtered and dried. When the resulting salt is heated with hydrochloric acid, a poisonous gas is released, and when it is heated in the presence of manganese dioxide, a gas that is part of the atmosphere is released. Write the equations for the reactions described.
C getting the answer
1) 4НCl + РbО 2 → РbС1 2 ↓ +2Н 2 О+ Cl 2
2) 6KOH+ 3Cl 2 →5KS1+KS1O 3 +3H 2 O
3) KS1O 3 +6HC1→KS1+3C1 2 +3H 2 O
4) 2KS1O 3 →2KS1+3O 2
5) Excess sodium hydroxide solution was added to the aluminum sulfate solution. Hydrochloric acid was added to the resulting solution in small portions, and the formation of a voluminous 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 for the written reactions.
1) A1 2 (SO 4) 3 + 8NaOH→2Na+3Na 2 SO 4 or A1 2 (SO 4) 3 + 12NaOH→2Na 3 +3Na 2 SO 4
2) Na 3 +3HC1→3NaС1+Al(OH) 3 ↓+3H2O
3) Al(OH) 3 ↓+3HC1 → A1C1 3 +3H 2 O
4) 2AlС1 3 +3H 2 O+3Na 2 CO 3 →3СО 2 +2А1(ОН) 3 ↓+6NaС1
6) After briefly heating an unknown orange powdery substance, 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 potassium hydroxide and heated, the resulting substance was added to a dilute solution of hydrochloric acid, and a green precipitate was formed, which dissolves in excess acid. Write the equations for the reactions described.
1)(NH 4) 2 Cr 2 O 7 →Cr 2 O 3 +N 2 +4H 2 O
2) Cr 2 O 3 + 4KOH→2KCrO 2 +H 2 O
3)KCrO 2 + HCl+H 2 O→Cr(OH) 3↓ +KCl
4) Cr(OH) 3 +3HCl (excess) →CrCl 3 +3H 2 O
7) Nitric acid was neutralized with baking soda, the neutral solution was carefully evaporated and the residue was calcined. The resulting substance was added to a solution of potassium permanganate acidified with sulfuric acid. the solution became discolored. The nitrogen-containing reaction product was placed in a solution of caustic soda and zinc dust was added, and a gas with a sharp characteristic odor was released. Write the equations for the reactions described.
1) NaHCO 3 +HNO 3 →NaNO 3 +CO 2 +H 2 O
2) 2 NaNO 3 →2NaNO 2 +O 2
3) 5 NaNO 2 +2KMnO 4 +3H 2 SO 4 →5NaNO 3 + K 2 SO 4 +Mn 2 SO 4 +3H 2 O
4) NaNO 3 +4Zn+7NaOH+6H 2 O→NH 3 +4Na 2
8) The substance obtained at the cathode during the electrolysis of molten sodium chloride was burned in oxygen. The resulting product was successively treated with sulfur dioxide and a barium hydroxide solution. Write the equations for the reactions described.
1) 2NaCl→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 → BaSO 4 ↓+2NaOH
9) Quicklime was calcined with excess coke. The reaction product after treatment with water is used to absorb sulfur dioxide and carbon dioxide. Write the equations for the reactions described
1) CaO + 3C → CaC 2 + CO
2) CaC 2 +2H 2 O→Ca(OH) 2 ↓+C 2 H 2
3) Ca(OH) 2 +CO 2 →CaCO 3 ↓+H 2 O or Ca(OH) 2 +2CO 2 →Ca(HCO 3) 2
4) Ca(OH) 2 +SO 2 →CaSO 3 ↓+H 2 O or Ca(OH) 2 +2SO 2 →Ca(HSO 3) 2
10) Copper wire was added to heated concentrated sulfuric acid and the resulting gas was passed through an excess of caustic soda. 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, and the formation of a precipitate and the release of a gas with a pungent odor were observed.
Write the equations for the reactions described
1) Cu+ 2H 2 SO 4 →CuSO 4 +SO 2 +2H 2 O
2) 2NaOH+ SO 2 →Na 2 SO 3 +H 2 O
3) Na 2 SO 3 +S→ Na 2 S 2 O 3
4) Na 2 S 2 O 3 + H 2 SO 4 → Na 2 SO 4 +SO 2 +S↓+H 2 O
11) The substance formed by the fusion of magnesium with silicon was treated with water, resulting in the formation of a precipitate and the release of a colorless gas. The precipitate was dissolved in hydrochloric acid, and the gas was passed through a solution of potassium permanganate. in this case, two water-insoluble binary compounds were formed. Write the equations for the reactions described
1) Si + 2Mg = Mg 2 Si
2) Mg 2 Si + 4H 2 O = 2Mg(OH) 2 + SiH 4
3) Mg(OH) 2 +2HCl→MgCl2 +2H2O
4) 3SiH 4 + 8KMnO 4 →8MnO 2 ↓+ 3SiO 2 ↓ +8KOH+ 2H 2 O
12 ) A solution of hydrochloric acid was added to a white, water-insoluble salt that occurs in nature as 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, formed a white precipitate, which dissolved when the gas was further passed through. When the resulting solution is boiled, a precipitate forms and gas is released. Write the equations for the reactions described.
1) CaCO 3 +2HC1 →CaC1 2 +CO 2 +H 2 O
2) Ca(OH) 2 +CO 2 →CaCO 3 ↓+H 2 O
3) CaCO 3 ↓+H 2 O +CO 2 →Ca(HCO 3) 2
4) Ca(HCO 3) 2 →CaCO 3 ↓+H 2 O+CO 2
13) The salt obtained by reacting zinc oxide with sulfuric acid was calcined at 800 0 C. The solid reaction product was treated with a concentrated alkali solution and carbon dioxide was passed through the resulting solution. Write the equations for the reactions described.
1) ZnO+H 2 SO 4 →ZnSO 4 +H 2 O
2) 2 ZnSO 4 →ZnO+2SO 2 +O 2
3) ZnO+2NaOH+H3O→Na 2
4) Na 2 +2CO 2 → 2NaHCO 3 +Zn(OH) 2 ↓ or Na 2 +CO 2 → Na 2 CO 3 +Zn(OH) 2 ↓ +H 2 O
14) Soda ash was added to the solution of trivalent chromium sulfate. The precipitate that formed was separated, transferred to a solution of sodium hydroxide, bromine was added and heated. After neutralizing the reaction products with sulfuric acid, the solution acquires an orange color, which changes to green after passing sulfur dioxide through the solution. Write the equations for the reactions described
1) Cr 2 (SO 4) 3 +3Na 2 CO 3 +3H 2 O →2Cr(OH) 3 ↓ + 3Na 2 SO 4 +3CO 2
2) 2Cr(OH) 3 + 10NaOH+3Br 2 →2Na 2 CrO 4 + 6NaBr+8H 2 O
3) 2Na 2 CrO+H 2 SO 4 →Na 2 Cr 2 O 7 +Na 2 SO 4 +H 2 O
4) Na 2 Cr 2 O 7 +3SO 2 +H 2 SO 4 →Na 2 SO 4 +Cr 2 (SO 4) 3 +H 2 O
15) Phosphine was passed through a hot solution of concentrated nitric acid. The reaction products were neutralized with quicklime, the precipitate that formed was separated, mixed with coke and silica and calcined. The reaction product, which glows in the dark, was heated in a solution of sodium hydroxide. Write the equations for the reactions described
1) PH 3 + 8HNO 3(clnts) → H 3 PO 4 + 8NO 2 +4H 2 O
2)2H 3 PO 4 +3CaO→Ca 3 (PO 4) 2 ↓+3H 2 O and 2HNO 3 +CaO→Ca(NO 3) 2 +H 2 O
3) Ca 3 (PO 4) 2 ↓+5C+3SiO 2 → 3CaSiO 3 +2P+ 5CO
4) P 4 +3 NaOH + 3H 2 O → 3NaH 2 PO 2 + PH 3
16) The black powder, which was formed when the red metal was burned in excess air, was dissolved in 10% sulfuric acid. Alkali was added to the resulting solution and the blue precipitate that formed was separated and dissolved in an excess of ammonia solution. Write the equations for the reactions described.
1) 2Cu+O 3 →2CuO
2) CuO +H 2 SO 4 →CuSO 4 +H 2 O
3) CuSO 4 +2NaOH →Cu(OH) 2 ↓+Na 2 SO 4
4) Cu(OH) 2 ↓+4NH 3 ∙H 2 O→(OH) 2 +4H 2 O
17) Red phosphorus was burned in a chlorine atmosphere. The reaction product was treated with excess water and powdered zinc was added to the solution. The released gas was passed over a heated plate of oxidized copper. Write the equations for the reactions described
1)2P+5Cl 2 →2PCl 5
2) PCl 5 +4H 2 O→ H 3 PO 4 +5HCl
3) 3Zn+2H 3 PO 4 →Zn 3 (PO 4) 2 ↓+3H 2 and Zn + 2HCl →ZnCl 2 +H 2
4) CuO+H 2 →Cu+H 2 O
18) The substance obtained at the anode by electrolysis of a sodium iodine solution on inert electrodes was reacted with potassium. The reaction product was heated with concentrated sulfuric acid and the liberated gas was passed through a hot solution of potassium chromate. Write the equations for the reactions described
1) 2КI +2H 2 O→2КOH+ I 2 ↓
2) I 2 +2K→ 2KI
3) 8KI+5H 2 SO 4 →4 I 2 ↓+H 2 S+4K 2 SO 4 +4H 2 O or 8KI+9H 2 SO 4 →4 I 2 ↓+H 2 S+8KHSO 4 +4H 2 O
4)3H 2 S+ 2K 2 CrO 4 +2H 2 O→2Cr(OH) 3 ↓+3S↓+4KOH
19) The gas formed as a result of the reaction of hydrogen chloride with a hot solution of potassium chromate reacts with iron. The reaction product was dissolved in water and sodium sulfide was added to it. The lighter substance from the resulting insoluble compounds was separated and reacted with concentrated sulfuric acid while heating. Write the equations for the reactions described.
1) 2K 2 CrO 4 +16HCl →4КCl+2CrCl 7 +3Cl 2 +H 2 O
2) 2Fe+3Cl 2 →2FeCl 3
3) 2FeCl 3 +3Na 2 S→S↓+FeS↓+6NaCl
4) S +2H 2 SO 4 →2SO 2 +2H 2 O
20) Two salts turn the flame purple. One of them is colorless, and when it is slightly heated with concentrated sulfuric acid, the liquid in which copper dissolves is distilled off; the latter transformation is accompanied by the release of brown gas. When a second salt of a 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 for the reactions described
1) KNO 3 +2H 2 SO 4 →KHSO 4 +HNO 3
2) Cu+4HNO 3(conc) →Cu(NO 3) 2 +2NO 2 +2H 2 O
3) 2K 2 CrO 4 +H 2 SO 4 →K 2 Cr 2 O 7 +K 2 SO 4 +H 2 O
4) K 2 Cr 2 O 7 +2KOH→2K 2 CrO 4 +H 2 O
Task 32 on the Unified State Exam in Chemistry (former task C2 of the “new type”) contains a description of an experiment consisting of sequential chemical reactions and laboratory methods for separating reaction products ( thought experiment).
According to my observations, many students find this task difficult. To a large extent, this is explained by the increasingly academic nature of teaching chemistry in schools and courses, when insufficient attention is paid to studying the features of working in the laboratory and actually conducting laboratory experiments.
Therefore, I decided to systematize and summarize the material according to the so-called. "laboratory" chemistry. This article discusses examples of task 32 in the Unified State Exam in Chemistry 2018 (former task C2), with a detailed analysis and analysis of the solution.
To complete this assignment you will need a good understanding of some topics in general chemistry and the chemistry of the elements, namely: basic , chemical properties and preparation, acids, and salts, and the relationship between various classes of inorganic substances; properties of simple substances - metals and non-metals; ; ; , , halogens.
- The solution obtained by reacting 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 for the reactions described.
Analysis and solution.
"Keywords" - concentrated nitric acid and copper.
Copper is a low-active metal and exhibits the properties of a reducing agent.
Keywords: " … The resulting product was successively treated with sulfur dioxide and barium hydroxide solution". The sodium sulfate obtained in the previous step undergoes an ion exchange reaction with barium hydroxide to precipitate barium sulfate (Equation 4).
1) 2NaCl = 2Na + Cl2
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 containing phosphorus (V) oxide. Write the equations for the reactions described.
Analysis and solution.
Keywords: " Ammonium chloride decomposition products..." Ammonium chloride is a salt that decomposes when the solid salt is heated into ammonia gas 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 occurring between substances. The simple substance copper is chemically inactive and does not react with phosphorus. The simple substance nitrogen is also chemically inactive and does not react with phosphorus (V) oxide. But water vapor reacts well with acidic phosphorus oxide (V) to form ortho-phosphoric acid (equation 4).
1) NH 4 Cl = 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 = 2H 3 PO 4
6. A solution of hydrochloric acid was added to a water-insoluble white salt, which occurs in nature as 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, produced a white precipitate; the precipitate dissolved upon further passage of gas. When the resulting solution is boiled, a precipitate forms. Write the equations for the reactions described.
Analysis and solution.
It is well known from a school chemistry course that a white, water-insoluble salt that 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).
Gas produced passed through lime water Ca(OH)2. Carbon dioxide is a typical acidic oxide that, when reacted with an alkali, forms a salt, calcium carbonate (Equation 2). Further the precipitate dissolved upon further passage of gas. A very important property is considered here: medium salts of polybasic acids under the influence of excess acid form more acidic salts . Calcium carbonate in excess 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 largely consist of the properties of the compounds that form acid salts. The properties of calcium bicarbonate are determined by the properties of the compounds that form it - carbonic acid H 2 CO 3 and calcium carbonate. It is easy to deduce that when boiled, bicarbonate will decompose into calcium carbonate (dissolves 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 = CaCO 3 + H 2 O
3) CaCO 3 + H 2 O + CO 2 = Ca(HCO 3) 2
4) Ca(HCO 3) 2 = CaCO 3 + H 2 O + CO 2
7. Substance obtained from anode during electrolysis of a 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 for the reactions described.
Analysis and solution.
Electrolysis of a sodium iodide solution with inert electrodes is described by the equation:
1. 2NaI + 2H 2 O = 2NaOH + H 2 + I 2
2. I 2 0 + H 2 S -2 = 2HI - + S 0
In this case, solid sulfur was formed. Sulfur reacts with aluminum when fused to form aluminum sulfide. Most nonmetals react with metals to form binary compounds:
3. 3S 0 + 2Al 0 = Al 2 +3 S 3 -2
The product of the reaction 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 = 2Al(OH) 3 + 3H 2 S
Such reactions are also called reactions. Cases of irreversible hydrolysis are discussed in detail in.
8 . The gas released when hydrogen chloride reacts with potassium permanganate reacts with iron. The reaction product was dissolved in water and sodium sulfide was added to it. The lighter of the resulting insoluble substances was separated and reacted with hot concentrated nitric acid. Write the equations for the reactions described.
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 chlorine gas was passed through, and the solution acquired a yellow color. The solution was acidified with sulfuric acid, as a result the color changed to orange; The gas released when the sulfide was treated with water was passed through the resulting solution, and the color of the solution changed to green. Write the equations for the reactions described.
Analysis and solution.
Keywords: " Chromium (III) sulfide was treated with water, gas was released and an insoluble substance remained«. Chromium (III) sulfide decomposes under the influence 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 = 2Cr(OH) 3 + 3H 2 S
Key words: “...a solution of caustic soda was added and chlorine gas was passed through, and the solution acquired a yellow color.” Under the influence of chlorine in an alkaline environment, chromium +3 is oxidized to chromium +6 . Chromium +6 forms an acidic 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«. Chromate salts transform into dichromates in an acidic environment. Yellow sodium chromate in an acidic environment 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 when treating the 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 reacted with hydrogen sulfide, it is reduced to trivalent chromium salt. Chromium (III) compounds are amphoteric and form salts in an acidic environment. Chromium (III) salts 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 a salt of an unknown metal under the influence of light. When this metal is dissolved in dilute nitric acid, a colorless gas is released, which in air quickly changes its color to brown, and a salt is formed that reacts with sodium bromide to form a cheesy yellowish precipitate. The anion in the salt used in photography is the anion of an acid that is formed simultaneously with sulfuric acid by the reaction of bromine water and sulfur dioxide. Write the equations for the reactions described.
11. A solution of sodium hydroxide was added dropwise to the solution obtained by reacting aluminum with dilute sulfuric acid until a precipitate formed. The resulting white precipitate was filtered and calcined. The resulting substance was fused with sodium carbonate. Write the equations for the reactions described.
Analysis and solution.
When interacting with metals, dilute sulfuric acid behaves like an ordinary mineral acid. Metals located 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 = Al +3 2 (SO 4) 3 + 3H 0 2
Next, aluminum sulfate reacts 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 = 2Al(OH) 3 + 3Na 2 SO 4
The white precipitate is aluminum hydroxide, insoluble in water. P When ignited, insoluble hydroxides decompose into water and the corresponding oxide :
3. 2Al(OH) 3 = 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 the salts. Carbonate is a salt, which 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 = 2NaAlO 2 + CO 2
12. A direct electric current was passed through a solution of copper (II) chloride using graphite electrodes. 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 electrolysis product released at the anode was passed through a hot sodium hydroxide solution. Write the equations for the reactions described.
13. A simple substance obtained by heating a mixture of calcium phosphate with coke and silicon oxide is dissolved in a solution of potassium hydroxide. The released gaseous substance was burned, the combustion products were collected and cooled, and silver nitrate was added to the resulting solution. Write the equations for the reactions described.
14. The foul-smelling liquid formed by the reaction of hydrogen bromide with potassium permanganate was separated and heated with iron filings. The reaction product was dissolved in water and a solution of cesium hydroxide was added to it. The resulting precipitate was filtered and calcined. Write the equations for the reactions described.
15. Electrical discharges were passed over the surface of the caustic soda solution, causing the air to turn brown, and the color disappeared after some time. The resulting solution was carefully evaporated and it was determined that the solid residue was a mixture of two salts. Exposing a mixture of salts to air results in the formation of one substance. Write the equations for the reactions described.
16. Calcium was dissolved in water. When sulfur dioxide is passed through the resulting solution, a white precipitate is formed, which dissolves when excess gas is passed through. Adding alkali to the resulting solution leads to the formation of a white precipitate. Write the equations for the reactions described.
17. When a simple yellow substance is burned in air, a gas with a pungent odor is formed. This gas is also released when some mineral containing iron is roasted 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 the characteristic smell of rotten eggs. When the released gases interact with each other, the original simple substance is formed. Write the equations for the reactions described.
18. The gaseous product of the interaction of dry table salt with concentrated sulfuric acid was reacted with a solution of potassium permanganate. The released gas was passed through a solution of sodium sulfide. The resulting yellow precipitate dissolves in a concentrated solution of sodium hydroxide. Write the equations for the reactions described.
19. The gas formed when hydrogen chloride is passed through a hot solution of potassium chromate reacts with iron. The reaction product was dissolved in water and sodium sulfide was added to it. The lighter of the resulting insoluble substances was separated and reacted with concentrated sulfuric acid while heating. Write the equations for the reactions described.
20. The two salts contain the same cation. The thermal decay of the first of them resembles a volcanic eruption, with the release of a low-active colorless gas that is part of the atmosphere. When the second salt interacts with a solution of silver nitrate, a white cheesy 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 for the reactions described.
21. Excess sodium hydroxide solution was added to the aluminum sulfate solution. Hydrochloric acid was added to the resulting solution in small portions, and the formation of a voluminous 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 for the reactions described.
22. Electrical discharges were passed over the surface of the caustic soda solution poured into the flask, and the air in the flask turned brown, which disappeared after some time. The resulting solution was carefully evaporated and it was determined that the solid residue was a mixture of two salts. When this mixture is heated, gas is released and the only substance remains. Write the equations for the reactions described.
23. Zinc oxide was dissolved in a solution of hydrochloric acid and the solution was neutralized by adding sodium hydroxide. The released white gelatinous substance was separated and treated with an excess of alkali solution, and the precipitate was completely dissolved. Neutralization of the resulting solution with an acid, for example, nitric acid, leads to the re-formation of a gelatinous precipitate. Write the equations for the reactions described.
24. The substance obtained at the cathode during the electrolysis of molten copper (II) chloride reacts with sulfur. The resulting product was treated with concentrated nitric acid and the liberated gas was passed through a solution of barium hydroxide. Write the equations for the reactions described.
25. A mixture of calcium orthophosphate, coke and sand was heated in an electric oven. One of the products of this reaction can spontaneously ignite in air. The solid combustion product of this substance was dissolved in water when heated, and ammonia gas was passed through the resulting solution. Write the equations for the reactions described.
26. The substance obtained at the cathode by electrolysis of a solution of iron (II) chloride was fused with sulfur and the product of this reaction was fired. The resulting gas was passed through a solution of barium hydroxide. Write the equations for the reactions described.
27. Copper wire was added to heated concentrated sulfuric acid and the released gas was passed through an excess of caustic soda 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, and the formation of a precipitate and the release of a gas with a pungent odor were observed. Write the equations for the reactions described.
28. After briefly heating an unknown orange powdery substance, 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 potassium hydroxide and heated, the resulting substance was added to a dilute solution of hydrochloric acid, and a green precipitate was formed, which dissolves in excess acid. Write the equations for the reactions described.
29. Two salts turn the flame purple. One of them is colorless, and when it is slightly heated with concentrated sulfuric acid, the liquid in which copper dissolves is distilled off; the latter transformation is accompanied by the release of brown gas. When a second salt of a 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 for the reactions described.
30. A solution of iron(III) chloride was electrolyzed with graphite electrodes. The brown precipitate formed as a by-product of electrolysis was filtered and calcined. The substance formed at the cathode was dissolved in concentrated nitric acid when heated. The product released at the anode was passed through a cold solution of potassium hydroxide. Write the equations for the reactions described.
31. The gas released during the interaction of hydrogen chloride with berthollet salt was introduced into a reaction with aluminum. The reaction product was dissolved in water and sodium hydroxide was added until the precipitation stopped, which was separated and calcined. Write the equations for the reactions described.
32. The unknown salt is colorless and turns the flame yellow. When this salt is slightly heated with concentrated sulfuric acid, the liquid in which the copper dissolves is distilled off; the latter transformation is accompanied by the release 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 for the reactions described.
33. The substance obtained at the anode during the electrolysis of molten sodium iodide with inert electrodes was isolated and reacted with hydrogen sulfide. The gaseous product of the last reaction was dissolved in water and ferric chloride was added to the resulting solution. The resulting precipitate was filtered and treated with a hot sodium hydroxide solution. Write the equations for the reactions described.
34. The 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 lime milk. Write the equations for the reactions described.
35. A mixture of iron powder and a solid product obtained by the interaction of sulfur dioxide and hydrogen sulfide was heated without access to air. The resulting product was fired in air. The resulting solid reacts with aluminum, releasing large amounts of heat. Write the equations for the reactions described.
36. The black substance was obtained by calcining the precipitate that forms when solutions of sodium hydroxide and copper (II) sulfate react. When this substance is heated with coal, a red metal is obtained, which dissolves in concentrated sulfuric acid. Write the equations for the reactions described.
37. A simple substance, a mixture of which with Berthollet salt is used in matches and ignites when rubbed, was burned in excess oxygen. The white solid resulting from combustion was dissolved in excess sodium hydroxide solution. The resulting salt with a solution of silver nitrate forms a bright yellow precipitate. Write the equations for the reactions described.
38. Zinc was dissolved in very dilute nitric acid and excess alkali was added to the resulting solution, obtaining a clear solution. Write the equations for the reactions described.
39. 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 is released with the smell of rotten eggs. Write the equations for the reactions described.
40. The substance formed by adding zinc powder 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 released gases were passed through a solution of sodium hydroxide. Write the equations for the reactions described.
41. The gas released when heating 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 for the reactions described.
42. A mixture of two colorless, colorless and odorless gases A and B was passed through heating over a catalyst containing iron, and the resulting gas B was neutralized with a solution of hydrobromic acid. The solution was evaporated and the residue was heated with caustic potassium, resulting in the release of colorless gas B with a pungent odor. When gas B is burned in air, water and gas A are formed. Write the equations for the reactions described.
43. Sulfur dioxide was passed through a solution of hydrogen peroxide. The water was evaporated from the resulting solution and magnesium shavings were added to the residue. The released gas was passed through a solution of copper sulfate. The resulting black precipitate was separated and fired. Write the equations for the reactions described.
44. A solution of hydrochloric acid was added to a white salt insoluble in water, 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, when passed through lime water, a white precipitate formed, which dissolved with further passing gas. When excess lime water is added to the resulting solution, a precipitate forms. Write the equations for the reactions described.
45. When a certain mineral A, consisting of two elements, is fired, a gas is formed that has a characteristic pungent odor and discolors bromine water with the formation of two strong acids in solution. When substance B, consisting of the same elements as mineral A, but in a different ratio, interacts 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 for the reactions described.
46. The substance released at the cathode during the electrolysis of molten sodium chloride was burned in oxygen. The resulting product was placed in a gasometer filled with carbon dioxide. The resulting substance was added to the ammonium chloride solution and the solution was heated. Write the equations for the reactions described.
47. Nitric acid was neutralized with baking soda, the neutral solution was carefully evaporated and the residue was calcined. The resulting substance was added to a solution of potassium permanganate acidified with sulfuric acid, and the solution became colorless. The nitrogen-containing reaction product was placed in a solution of caustic soda and zinc dust was added, and a gas with a sharp characteristic odor was released. Write the equations for the reactions described.
48. When a solution of salt A reacted with an alkali, a gelatinous, water-insoluble blue substance was obtained, which was dissolved in colorless liquid B to form a blue solution. The solid product remaining after careful evaporation of the solution was calcined; in this case, two gases were released, one of which is brown in color, and the second is part of the atmospheric air, and a black solid remains, which dissolves in liquid B to form substance A. Write the equations for the reactions described.
49. White phosphorus dissolves in a solution of potassium hydroxide, releasing a gas with a garlicky odor, which spontaneously ignites 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 for the reactions described.
50. The 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 hydroxide were added to the remaining substance and heated for a long time at high temperature. Write the equations for the reactions described.
The gas released by the reaction of hydrogen chloride with potassium permanganate was passed through a solution of sodium tetrahydroxoaluminate. The resulting precipitate was filtered, calcined, and the solid residue was treated with hydrochloric acid. Write the equations for the reactions described.
The nitrogen-hydrogen mixture was heated to a temperature of 500°C and passed under high pressure 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 gas released was passed over copper while heating, resulting in the formation of a black solid. Write the equations for the reactions described.
Trivalent chromium hydroxide was treated with hydrochloric acid. Potash was added to the resulting solution, the precipitate that formed was separated and added to a concentrated solution of potassium hydroxide, as a result of which the precipitate dissolved. After adding excess hydrochloric acid, a green solution was obtained. Write the equations for the reactions described.
The substance obtained at the anode by electrolysis of a sodium iodide solution with inert electrodes was reacted with potassium. The reaction product was heated with concentrated sulfuric acid and the liberated gas was passed through a hot solution of potassium chromate. Write the equations for the reactions described.
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 some time it was filtered. A solution of potassium hydroxide was added to the filtrate, the precipitate that formed was separated and left in air, and the color of the substance changed. Write the equations for the reactions described.
One of the substances formed when silicon oxide fuses 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 for the reactions described.
The solid substance formed by the interaction of sulfur dioxide and hydrogen sulfide interacts with aluminum when heated. The reaction product was dissolved in dilute sulfuric acid and potash was added to the resulting solution. Write the equations for the reactions described.
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 to release carbon dioxide, and a gaseous simple substance that supports combustion. Write the equations for the reactions described.
The reaction product of nitrogen and lithium was treated with water. The gas released as a result of the reaction was mixed with excess oxygen and, when heated, passed over a platinum catalyst; the resulting gas mixture was brown in color. Write the equations for the reactions described.
Copper turnings were dissolved in dilute nitric acid and the solution was neutralized with caustic potassium. The released blue substance was separated, calcined (the color of the substance changed to black), mixed with coke and calcined again. Write the equations for the reactions described.
Phosphorus was burned in excess chlorine, the resulting solid was mixed with phosphorus and heated. The reaction product was treated with water, which released a colorless gas with a pungent odor. The solution was added to a solution of potassium permanganate acidified with sulfuric acid, which became discolored as a result of the reaction. Write the equations for the reactions described.
Ferric chloride was treated with concentrated nitric acid while 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. Hydrogen gas was passed over the resulting substance while heating. Write the equations for the reactions described.
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, releasing a very light colorless gas, which is used to obtain metals, such as copper, from their oxides. Write the equations for the reactions described.
Magnesium silicide was treated with a solution of hydrochloric acid and the resulting gas was burned. The solid reaction product was mixed with soda ash, the mixture was heated until melting and kept for some time. After cooling, the reaction product (widely used as “liquid glass”) was dissolved in water and treated with a solution of sulfuric acid. Write the equations for the reactions described.
A gas mixture of ammonia and a large excess of air was passed through while heating over platinum, and the reaction products were absorbed after some time by a solution of sodium hydroxide. After evaporation of the solution, a single product was obtained. Write the equations for the reactions described.
Soda ash was added to the ferric chloride solution and the precipitate that formed was separated and calcined. Carbon monoxide was passed over the resulting substance while heating, and the solid product of the last reaction was introduced into interaction with bromine. Write the equations for the reactions described.
The reaction product of sulfur with aluminum (the reaction occurs 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 for the reactions described.
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 substances formed spontaneously ignites in air. Write the equations for the reactions described.
Brown gas was passed through an excess of caustic potassium solution in the presence of a large excess of air. Magnesium shavings were added to the resulting solution and heated; The released gas neutralized nitric acid. The resulting solution was carefully evaporated, and the solid reaction product was calcined. Write the equations for the reactions described.
Iron scale was dissolved in concentrated nitric acid while heating. The solution was carefully evaporated and the reaction product was dissolved in water. Iron powder was added to the resulting solution, after some time the solution was filtered and the filtrate was treated with a solution of potassium hydroxide, resulting in a light green precipitate that quickly darkened in air. Write the equations for the reactions described.
A solution of aluminum chloride was added to the soda ash solution, the released substance was separated and added to the sodium hydroxide solution. 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 for the reactions described.
Copper shavings were added to the mercury(II) nitrate solution. After the reaction was completed, the solution was filtered and the filtrate was added dropwise to a solution containing sodium hydroxide and ammonium hydroxide. In this case, a short-term formation of a precipitate was observed, which dissolved to form a bright blue solution. When an excess of sulfuric acid solution was added to the resulting solution, a color change occurred. Write the equations for the reactions described.
The reaction product of magnesium phosphide with water was burned and the reaction products were absorbed by water. The resulting substance is used industrially to produce double superphosphate from phosphorite. Write the equations for the reactions described.
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 transformations described.
Iron powder was added to the ferric chloride solution and after some time the solution was filtered. Sodium hydroxide was added to the filtrate, the resulting precipitate was separated and treated with hydrogen peroxide. An excess of caustic potassium solution and bromine were added to the resulting substance; As a result of the reaction, the color of bromine disappeared. Write the equations for the reactions described.
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, resulting in the release of a gas used in medicine. Write the equations for the reactions described.
Sulfur dioxide was passed through a solution of hydrogen peroxide. The solution was evaporated and copper filings were added to the remaining liquid. The released gas was mixed with the gas that is formed when iron (II) sulfide reacts with a solution of hydrobromic acid. Write the equations for the reactions described.
When dilute hydrochloric acid was added to the solution of a yellow salt, which colors the flame violet, the color changed 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 and a solution of silver nitrate was added to the filtrate. Write the equations for the reactions described.
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 until melting. After cooling the melt, it was treated with water and nitric acid was added to the resulting solution. Write the equations for the reactions described.
The insoluble substance formed when sodium hydroxide is added to a solution of ferric chloride was separated and dissolved in dilute sulfuric acid. Zinc dust was added to the resulting solution, the resulting precipitate was filtered and dissolved in concentrated hydrochloric acid. Write the equations for the reactions described.
Aluminum nitrate was calcined, the reaction product was mixed with soda ash and heated until melting. The resulting substance was dissolved in nitric acid and the resulting solution was neutralized with an ammonia solution, and the release of a voluminous gelatinous precipitate was observed. Write the equations for the reactions described.
Magnesium nitride was treated with excess water. When the released gas is passed 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 for the reactions described.
Chlorine water smells like chlorine. When alkalizing, the smell disappears, and when hydrochloric acid is added, it becomes stronger than before. Write the equations for the reactions described.
The solid 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, added to a solution of sodium chloride containing copper filings, and a precipitate was formed. Write the equations for the reactions described.
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 solution of sodium hydroxide. Write the equations for the reactions described.
Iron powder was dissolved in a large amount of dilute sulfuric acid and air was passed through the resulting solution, followed by a gas that smelled like rotten eggs. The resulting insoluble salt was separated and dissolved in a hot solution of concentrated nitric acid. Write the equations for the reactions described.
Colorless gases are released when concentrated sulfuric acid is mixed with both sodium chloride and sodium iodide. When these gases are passed through an aqueous ammonia solution, salts are formed. Write the equations for the reactions described.
Magnesium powder was mixed with silicon and heated. The reaction product was treated with cold water and the resulting gas was passed through hot water. The resulting precipitate was separated, mixed with caustic soda and heated until melting. Write the equations for the reactions described.
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 for the reactions described.
The salt obtained by dissolving copper in dilute nitric acid was subjected to electrolysis using graphite electrodes. The substance released at the anode was reacted with sodium, and the resulting reaction product was placed in a vessel with carbon dioxide. Write the equations for the reactions described.
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 neutralizing the solution with alkali, a voluminous white (light green) precipitate is formed. When substance A is fired, two oxides are formed. One of them is a gas that has a characteristic pungent odor and discolors bromine water with the formation of two strong acids in solution. Write the equations for the reactions described.
Magnesium was heated in a vessel filled with ammonia gas. 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 for the reactions described.
Soda ash was added to the solution of trivalent chromium sulfate. The resulting precipitate was separated, transferred to a solution of sodium hydroxide, bromine was added and heated. After neutralizing the reaction products with sulfuric acid, the solution acquires an orange color, which disappears after passing sulfur dioxide through the solution. Write the equations for the reactions described.
Quicklime was calcined with excess coke. The reaction product after treatment with water is used to absorb sulfur dioxide and carbon dioxide. Write the equations for the reactions described.
Ferrous sulfide was treated with a solution of hydrochloric acid, the resulting gas was collected and burned in 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 for the reactions described.
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, obtaining a black substance, which was heated in excess of ammonia (gas). Write the equations for the reactions described.
Red phosphorus was burned in a chlorine atmosphere. The reaction product was treated with excess water and powdered zinc was added to the solution. The released gas was passed over heated ferrous oxide. Write the reaction equations for the transformations described.
The silver-gray metal, which is attracted by a magnet, was added to 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 while heating. Write the equations for the reactions described.
Magnesium turnings 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 for the reactions described.
During the thermal decomposition of salt A in the presence of manganese dioxide, 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 interacts 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 forms. Write the equations for the reactions described.
The precipitate obtained by adding caustic soda to a solution of aluminum sulfate was separated, calcined, mixed with soda ash and heated until melting. After treating the residue with sulfuric acid, the original aluminum salt was obtained. Write the equations for the reactions described.
The substance formed when magnesium fuses with silicon was treated with water, resulting in the formation of a precipitate and the release of a colorless gas. The precipitate was dissolved in hydrochloric acid, and the gas was passed through a solution of potassium permanganate, which resulted in the formation of two water-insoluble binary substances. Write the equations for the reactions described.
The substance obtained by heating iron scale in a hydrogen atmosphere was added to hot concentrated sulfuric acid and heated. The resulting solution was evaporated, the residue was dissolved in water and treated with a solution of barium chloride. The solution was filtered and a copper plate was added to the filtrate, which dissolved after some time. Write the equations for the reactions described.
The quicklime was “quenched” with water. Gas, which is released during the calcination of sodium bicarbonate, was passed into the resulting solution, and the formation and subsequent dissolution of a precipitate was observed. Write the equations for the reactions described.
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 precipitate that formed, milk of lime was added and heated. Write the equations for the reactions described.
Give examples of interaction:
two acids
two bases
two acid salts
two acid oxides
Write the equations for the reactions described.
A solution of medium salt, formed when sulfur dioxide is passed through an alkali solution, was left in air for a long time. The solid formed after the solution evaporated was mixed with coke and heated to high temperature. When hydrochloric acid is added to a solid reaction product, a gas is released that smells like rotten eggs. Write the equations for the reactions described.
A solution of dilute sulfuric acid was added to the black powdery substance and heated. A solution of caustic soda was added to the resulting blue solution until the precipitation stopped. The precipitate was filtered and heated. The reaction product was heated in a hydrogen atmosphere, resulting in a red substance. Write the equations for the reactions described.
Red phosphorus was burned in an atmosphere of chlorine and a small amount (a few drops) of water was added to the reaction product. The released 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 cuprous oxide. Write the reaction equations for the transformations described.
A solution of iron(III) chloride was electrolyzed with graphite electrodes. The brown precipitate formed during electrolysis was filtered and dissolved in a sodium hydroxide solution, after which the amount of sulfuric acid necessary to form a clear solution was added. The product released at the anode was passed through a hot solution of potassium hydroxide. Write the equations for the reactions described.
Aluminum chloride was added to the solution of crystalline soda, the precipitate that formed was separated and treated with a solution of sodium hydroxide. The resulting solution was neutralized with nitric acid, the resulting precipitate was separated and calcined. Write the equations for the reactions described.
Ammonia was mixed with a large excess of air, heated in the presence of platinum and after some time absorbed by water. Copper shavings added to the resulting solution dissolve with the release of brown gas. Write the equations for the reactions described.
When a solution of acid A is added to manganese dioxide, a toxic 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, upon interaction with concentrated sulfuric acid, one can obtain the starting acid A, and a colorless gas that is part of the atmospheric air. Write the equations for the reactions described.
The product of the interaction of silicon with chlorine is easily hydrolyzed. When the solid hydrolysis product is fused with both caustic and soda ash, liquid glass is formed. Write the equations for the reactions described.
Caustic soda was added to the solution obtained by dissolving iron in hot concentrated hydrochloric acid. The resulting precipitate was separated, left in air for a long time, and then dissolved in dilute hydrochloric acid. Write the equations for the reactions described.
When the orange substance is heated, it 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 reacts with water, releasing a gas with a pungent odor that can reduce metals, such as copper, from their oxides. Write the equations for the reactions described.
The gas, which smelled like rotten eggs, 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 transformations described.
The salt obtained by dissolving iron in hot concentrated sulfuric acid was treated with an excess of sodium hydroxide solution. The brown precipitate that formed was filtered and calcined. The resulting substance was fused with iron. Write the equations for the reactions described.
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 separating the precipitate, magnesium shavings were added to the solution, the solution was filtered, the filtrate was evaporated and calcined. Write the equations for the reactions described.
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 and calcined. When heating the calcination product, which is black, with coke, a red starting material was obtained. Write the equations for the reactions described.
Iodine was heated with excess phosphorus and the reaction product was treated with a small amount of water. The gaseous reaction product was completely neutralized with a solution of sodium hydroxide and silver nitrate was added to the resulting solution. Write the equations for the reactions described.
The iron was 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 resulting precipitate was separated and treated with 20% sulfuric acid, obtaining an almost colorless solution. Write the equations for the reactions described.
The gas released when solid table salt is heated with concentrated sulfuric acid was passed through a solution of potassium permanganate. The gaseous reaction product was absorbed with a cold solution of sodium hydroxide. After adding hydroiodic acid to the resulting solution, a pungent odor appears and the solution acquires a dark color. Write the equations for the reactions described.
Through the solution obtained by slaking lime, gas was passed through, which is formed when producing quicklime from limestone; As a result, a white precipitate is released. When acetic acid acts on the resulting precipitate, the same gas is released that is formed during the calcination of calcium carbonate. Write the equations for the reactions described.
The red substance, which is used in the manufacture of matches, was burned in excess air and the reaction product, when heated, was dissolved in a large amount of water. After neutralizing the resulting solution with baking soda, silver nitrate was added to it. Write the equations for the reactions described.
The gas released when hydrochloric acid reacts with potassium permanganate is passed through a solution of sodium bromide. After the end of the reaction, the solution was evaporated, the residue was dissolved in water and subjected to electrolysis with graphite electrodes. The gaseous reaction products mixed with each other and illuminated, resulting in an explosion. Write the equations for the reactions described.
The gas produced by 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 for the reactions described.
Copper shavings were added to 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 for the reactions described.
Hydrochloric acid was added to solutions of substances A and B, which color the flame yellow: 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 lead (II) nitrate is passed through the solution. When a solution of substance B with hydrochloric acid is heated, the color of the solution changes from yellow to green and a poisonous yellow-green 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 for the reactions described.
A solution of hydrochloric acid was carefully added to the pyrolusite and the resulting gas was passed into a beaker half filled with a cold solution of potassium hydroxide. After the reaction was completed, the glass was covered with cardboard and left, while the glass was illuminated by the sun's rays; After some time, a smoldering splinter was brought into the glass, which flared up brightly. Write the equations for the reactions described.
The precipitate obtained by the interaction of a solution of aluminum salt 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 the formation of a precipitate. Write the equations for the described transformations.
The black powder, which was formed by prolonged heating of a red metal in excess air, was dissolved in 10% sulfuric acid to obtain a blue solution. Alkali was added to the solution and the precipitate that formed was separated and dissolved in an excess of ammonia solution. Write the equations for the reactions described.
Phosphorus was added to the solid that forms when phosphorus is burned in excess chlorine and the mixture was 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 for the reactions described.
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 for the reactions described.
Zinc nitrate was calcined, and 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 for the reactions described.
Two vessels contain solutions of unknown substances. When the first substance barium chloride is added to the solution, a white precipitate forms, insoluble in water and acids. A white precipitate also appears when a solution of silver nitrate is added to a sample taken from the second vessel. When a sample of the first solution with sodium hydroxide is heated, a pungent odor gas is released. When the second solution reacts with sodium chromate, a yellow precipitate forms. Write the equations for the reactions described.
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 for the reactions described.
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. Write down reaction equations for the transformations described.
Substances released at the cathode and anode during the electrolysis of a sodium iodide solution with graphite electrodes react with each other. The reaction product reacts with concentrated sulfuric acid to release a gas, which is passed through a solution of potassium hydroxide. Write the equations for the reactions described.
The substance that is formed during the electrolysis of bauxite melt in cryolite dissolves in both a hydrochloric acid solution and an alkali solution, releasing the same gas. When mixing the resulting solutions, a voluminous white precipitate is formed. Write the equations for the reactions described.
Concentrated hydrochloric acid was added to lead(IV) oxide while heating. The released gas was passed through a heated solution of caustic potassium. The solution was cooled, the oxygen-containing acid salt was filtered and dried. When the resulting salt is heated with hydrochloric acid, a poisonous gas is released, and when it is heated in the presence of manganese dioxide, a gas enters the atmosphere. Write the equations for the reactions described.
The brown precipitate obtained by reacting sodium sulfite with an aqueous solution of potassium permanganate was filtered and treated with concentrated sulfuric acid. When heated, the released gas reacts with aluminum, and the resulting substance reacts with a solution of hydrochloric acid. Write the reaction equations for the transformations described.
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 for the reactions described.
Silver nitrate was calcined and the solid reaction product was heated in oxygen. The resulting substance dissolves in an excess of concentrated ammonia. When hydrogen sulfide is passed through the resulting solution, a black precipitate is formed. Write the equations for the reactions described.
The solid that forms when phosphorus and phosphorus pentachloride are heated was dissolved in a large amount of water. Part of the resulting solution was added to a solution of potassium permanganate acidified with sulfuric acid, and the latter became discolored. Write the equations for the reactions described.
Several zinc granules were added to a vessel with concentrated sulfuric acid. The released gas was passed through a solution of lead (II) acetate, the precipitate was separated, fired, and the resulting gas was reacted with an aqueous solution of potassium permanganate. Write the equations for the reactions described.
Several granules of zinc were dissolved by heating in a solution of sodium hydroxide. Nitric acid was added to the resulting solution in small portions 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 for the reactions described.
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 for the reactions described.
A solution of iron(III) chloride was electrolyzed with graphite electrodes. The resulting brown precipitate (a by-product of electrolysis) was filtered, calcined and fused with the substance formed at the cathode. Another substance, also released at the cathode, was introduced into a reaction with the product released during electrolysis at the anode; the reaction occurs under illumination and with an explosion. Write the equations for the reactions described.
A white, water-insoluble salt that meets found in nature in the form of a mineral widely used in construction and architecture, calcined at 1000°C. After cooling, water was added to the solid residue and the gaseous product of the decomposition reaction was passed through the resulting solution, resulting in the formation of a white precipitate, which dissolved with further passage of gas. Write the equations for the reactions described.
