1. Silicon oxide was calcined with a large excess of magnesium. The resulting mixture of substances was treated with water. At the same time, gas was released, which was burned in oxygen. The solid combustion product was dissolved in a concentrated solution of cesium hydroxide. Hydrochloric acid was added to the resulting solution. Write the equations for the four reactions described.
2. 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 down the equations for the reactions described. Write the equations for the four reactions described.
3. The gas formed during the combustion of coke has been in contact with hot coal for a long time. The resulting reaction product was subsequently passed through a layer of heated iron ore and a layer of quicklime. Write down the equations for the reactions described.
3CO + Fe2O3 = 2Fe + 3CO2
CO2 + CaO = CaCO3
4 .. Copper shavings were added to the heated concentrated sulfuric acid. The evolved gas was passed through an excess of sodium hydroxide solution. The reaction product was isolated, dissolved in water, and elemental sulfur was added, which dissolved as a result of heating the mixture. Dilute sulfuric acid was added to the resulting solution. Write down the equations for the reactions described.
Cu + 2H2SO4 = CuSO4 + SO2 + 2H2O
SO2 + 2NaOH = Na2SO3 + H2O
Na2SO3 + H2O = NaHSO3 + NaOH (first stage of hydrolysis)
3S + 6NaOH = 2Na2S + Na2SO3 + 3H2O
Na2S + H2SO4 = H2S + Na2SO4
2-7. Obtaining a black and white image in photography is based on the decomposition of a metal salt under the action of light. When this metal dissolves in dilute nitric acid, a colorless gas is released, which in air quickly changes its color to brown, and the salt interacts with sodium bromide to form a yellowish curdled precipitate.
Salt used in photography contains an anion of an acid produced at the same time
with sulfuric acid in the interaction of bromic water and sulfur dioxide. Write equations
described reactions.
2AgBr = 2Ag + Br2
3Ag + 4HNO3 = 3AgNO3 + NO + 2H2O
AgNO3 + NaBr = AgBr + NaNO3
SO2 + 2H2O + Br2 = H2SO4 + 2HBr
2-8. The substance obtained at the cathode during the electrolysis of sodium chloride melt was burned in oxygen. The resulting product was sequentially treated with sulfur dioxide and barium hydroxide solution. Write down the equations for the reactions described.
2NaCl = 2Na + Cl2
2Na + O2 = Na2O2 (peroxide)
Na2O2 + SO2 = Na2SO4
Na2SO4 + Ba (OH) 2 = BaSO4 + 2NaOH
2-9. A solution of hydrochloric acid was added to the insoluble white salt, which occurs in nature in the form of a mineral widely used in architecture and construction, as a result of which the salt dissolved, a gas was released, when passed through lime water, a white precipitate formed. The precipitate dissolved upon further gas passage. When the resulting solution was boiled, a precipitate formed. Write down the equations for the reactions described.
CaCO3 + 2HCl = CaCl2 + H2O + CO2
CO2 + Ca (OH) 2 = CaCO3 + H2O
CaCO3 + CO2 + H2O = Ca (HCO3) 2
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 sodium hydroxide. A solution of barium chloride was added to the resulting solution. The resulting precipitate was treated with an excess of 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 acted upon with concentrated sulfuric acid under low heating, the resulting gas was passed into a solution of barium hydroxide. Potassium sulfate solution was added to the resulting solution. The resulting precipitate was fused with coal. The resulting material was treated with hydrochloric acid.
5) A sample of aluminum sulfide was treated with hydrochloric acid. In this case, gas was evolved 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 hydrogen peroxide solution.
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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, while 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 sodium sulfite solution. To the resulting solution, a solution of barium chloride was added first, and after separation of 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. The result is a yellow solution, which becomes orange when added with sulfuric acid. 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 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 down 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. Potassium iodide solution was added to one part, and silver nitrate solution to the second. In both cases, the formation of a precipitate was observed. Write the equations for the four reactions described.
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. Dissolution proceeded with the evolution of brown gas. Write the equations for the four reactions described.
13) Iron was burned in a chlorine atmosphere. 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 reactions described.
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 the sodium carbonate solution, precipitation was again observed. Write the equations for the four reactions described.
15) As a result of incomplete combustion of coal, a gas was obtained, in a stream of which iron (III) oxide was heated. The resulting material was dissolved in hot concentrated sulfuric acid. The resulting salt solution was subjected to electrolysis. Write the equations for the four reactions described.
16) Some zinc sulfide was divided into two parts. One of them was treated with nitric acid, and the other was fired in air. A simple substance was formed during the interaction of the evolved gases. This substance was heated with concentrated nitric acid, and a brown gas was evolved. Write the equations for the four reactions described.
17) Potassium chlorate was heated in the presence of a catalyst, while a colorless gas was evolved. By burning iron in an atmosphere of this gas, iron scale was obtained. It was dissolved in an excess of hydrochloric acid. To the resulting solution was added a solution containing sodium dichromate and hydrochloric acid.
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1) 2КClО 3 → 2КСl + 3О 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 НСІ → 6 FeCl 3 + 2 CrCl 3 + 2NaCl + 7Н 2 О 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 off and calcined. The resulting substance was dissolved in hydroiodic acid. Write the 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, while the formation of a precipitate was observed first, and then its complete dissolution. The resulting iodine-containing acid was isolated from the solution, dried and heated carefully. The resulting oxide reacted with carbon monoxide. Write down the equations of the described reactions.
20) Powder of chromium (III) sulfide 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 precipitate that formed was treated with an excess of concentrated potassium hydroxide solution until it was completely dissolved. To the resulting solution was added a solution of aluminum chloride and again observed the formation of a white precipitate. Write down the equations of the described reactions.
22) Potassium nitrate was heated with powdered lead until the reaction was terminated. The product mixture was treated with water, and then the resulting solution was filtered. The filtrate was acidified with sulfuric acid and treated with potassium iodide. The separated 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.
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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 with heating. The gas released during this process 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 was heated carefully. 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 obtained 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 introduced into the ammonium chloride solution. The released gas with a pungent odor is absorbed by the sulfuric acid. The resulting middle salt was calcined. Write down the equations of the described reactions.
27) Chlorine has reacted with hot potassium hydroxide solution. When the solution was cooled, crystals of Berthollet's salt precipitated. The crystals obtained were introduced into a hydrochloric acid solution. The resulting simple substance reacted with metallic iron. The reaction product was heated with a new portion 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 resulting brown precipitate was filtered off and calcined. The resulting substance was fused with iron. Write the 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 oxide (III) was heated. The resulting material was dissolved in hot concentrated sulfuric acid. The resulting salt solution was treated with an excess of potassium sulfide solution.
31) Some zinc sulfide was split in two. One of them was treated with hydrochloric acid, and the other was fired in air. A simple substance was formed during the interaction of the evolved gases. 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 during this was burned in an excess of oxygen. The combustion products were absorbed in an aqueous solution of iron sulfate (III).
Metallic aluminum was dissolved in hydroxide solution
Carbon dioxide. The precipitate that formed was calcined and the resulting
The product was fused with sodium carbonate.
1) 2Al + 2NaOH + 6H 2 O = 2Na + 3H 2
2) Na + CO 2 = NaHCO 3 + Al (OH) 3 ↓
3) 2Al (OH) 3 Al 2 O 3 + 3H 2 O
4) Al 2 O 3 + Na 2 CO 3 2NaAlO 2 + CO 2
Metallic copper was treated with iodine while heating.
Sulfuric acid when heated. The resulting solution
Treated with potassium hydroxide. The precipitate that formed was calcined.
Write down 4 equations of the described reactions.
1) 2Cu + I 2 = 2CuI
2) 2CuI + 4H 2 SO 4 2CuSO 4 + 2SO 2 + I 2 + 4H 2 O
3) CuSO 4 + 2KOH = Cu (OH) 2 ↓ + K 2 SO 4
4) Cu (OH) 2 CuO + H 2 O
The precipitate that formed was calcined, and the resulting product was heated in
Atmosphere of hydrogen. The resulting powder was dissolved in
Diluted nitric acid.
Write down 4 equations of the described reactions.
1) 2CuCl 2 + 2Na 2 CO 3 + H 2 O = (CuOH) 2 CO 3 ↓ + CO 2 + 4NaCl
2) (CuOH) 2 CO 3 2CuO + H 2 O + CO 2
3) CuO + H 2 Cu + H 2 O
4) 3Cu + 8HNO 3 = 3Cu (NO 3) 2 + 2NO + 4H 2 O
4. The reaction product of lithium with nitrogen was treated with water. The resulting gas was passed through a sulfuric acid solution until the termination of chemical reactions. The resulting salt was mixed with sodium nitrite solution and heated.
1) 6Li + N 2 = 2Li 3 N
2) Li 3 N + 3H 2 O = 3LiOH + NH 3
3) 2NH 3 + H 2 SO 4 = (NH 4) 2 SO 4
4) (NH 4) 2 SO 4 + 2NaNO 2 = Na 2 SO 4 + 2N 2 + 4H 2 O
5. A weighed portion of aluminum was dissolved in dilute nitric acid,
in this case, a gaseous simple substance was released. To the received
Strip. The precipitate that formed was filtered off and calcined, the filtrate was evaporated, the resulting solid residue was fused with ammonium chloride.
1) 10Al + 36HNO 3 = 10Al (NO 3) 3 + 3N 2 + 18H 2 O
2) 2Al (NO 3) 3 + 3Na 2 CO 3 + 3H 2 O = 2Al (OH) 3 ↓ + 3CO 2 + 6NaNO 3
3) 2Al (OH) 3 → Al 2 O 3 + 3H 2 O
4) NaNO 3 + NH 4 Cl = N 2 O + 2H 2 O + NaCl
6. Hydrogen sulfide was passed through an excess of sodium hydroxide solution, then a solution of iron (II) chloride was added. The resulting precipitate was calcined. The resulting gas was mixed with oxygen and passed over the catalyst.
7. The magnesium silicide was treated with water. At the same time, gas was released, which was burned in oxygen. The solid combustion product was dissolved in a concentrated solution of cesium hydroxide. Hydrochloric acid was added to the resulting solution.
8 ... Zinc nitrate was calcined, the resulting solid precipitate was dissolved in sulfuric acid. Hydrogen sulfide was passed through the solution, the resulting black precipitate was dissolved by heating in concentrated nitric acid.
9. 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. The resulting solution was treated with excess phosphoric acid.
10. 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.
11 ... Dry sodium chloride was acted upon with concentrated sulfuric acid under weak heating, the resulting gas was passed into a solution of barium hydroxide. Potassium sulfate solution was added to the resulting solution. The resulting precipitate was fused with coal.
12 ... A weighed portion of aluminum sulfide was treated with hydrochloric acid. In this case, gas was evolved and a colorless solution was formed. Ammonia water was added to the resulting solution, and the gas was passed through a solution of lead nitrate. The resulting precipitate was treated with a hydrogen peroxide solution.
13 ... Aluminum sulfide was treated with water, while gas was evolved 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.
14. The potassium iodide solution was treated with chlorine. The resulting precipitate was treated with sodium sulfite solution. To the resulting solution, a solution of barium chloride was added first, and after separation of the precipitate, a solution of silver nitrate was added.
15. A gray-green powder of chromium (III) oxide was fused with an excess of alkali, the resulting substance was dissolved in water. Hydrogen peroxide was added to the resulting alkaline solution. The result is a yellow solution, which becomes orange when added with sulfuric acid. When hydrogen sulfide is passed through the resulting acidified orange solution, it becomes cloudy and turns green.
16. Silicon was dissolved in concentrated potassium hydroxide solution. 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.
1. An odorless, colorless gas A, which forms an explosive mixture with oxygen, reacts under illumination with a simple gaseous substance B of a yellow-green color with an explosion, forming a colorless gas C with a pungent odor. An aqueous solution of substance C, acting on sodium sulfide, releases a poisonous gas with an unpleasant odor. When it interacts with sulfur dioxide, a simple yellow solid substance is formed. Write down the reaction equations.
2. Crystalline substance A of bright red color, when dissolved in alkali, forms yellow salt B. Under the action of an acid, substance B is converted into an orange salt C. Salt C reacts with concentrated hydrochloric acid, producing a yellow-green gas that oxidizes even gold. Write down the reaction equations.
3. Substance A, which is part of one of the most abundant minerals in the earth's crust, decomposes at high temperatures into two oxides, one of which, B, is always formed during life. When substance B interacts with graphite, when heated, gas C, toxic for warm-blooded animals, is obtained, colorless and odorless, combustible. With this gas, iron is reduced from its trivalent oxide. Write down the reaction equations.
4. The silvery-white metal A reacts with a dilute solution of sulfuric acid to form salt B. When added to an aqueous solution of salt B alkali, a precipitate is formed, which immediately turns green in air and then quickly acquires a brown color. With prolonged heating, this precipitate dissolves in a concentrated alkali solution. Write down the reaction equations.
The sodium was heated in a hydrogen atmosphere. On adding water to the obtained substance, gas evolution and the formation of a clear solution were observed. A brown gas was passed through this solution, which was obtained as a result of the interaction of copper with a concentrated solution of nitric acid. Write the equations for the four reactions described.
1) When sodium is heated in a hydrogen atmosphere (T = 250-400 o C), sodium hydride is formed):
2Na + H 2 = 2NaH
2) When water is added to sodium hydride, alkali NaOH is formed, and hydrogen is released:
NaH + H 2 O = NaOH + H 2
3) When copper interacts with a concentrated solution of nitric acid, brown gas is released - NO 2:
Cu + 4HNO 3 (conc.) = Cu (NO 3) 2 + 2NO 2 + 2H 2 O
4) When the brown gas NO 2 is passed through an alkali solution, a disproportionation reaction occurs - nitrogen N +4 is simultaneously oxidized and reduced to N +5 and N +3:
2NaOH + 2NO 2 = NaNO 3 + NaNO 2 + H 2 O
(disproportionation reaction 2N +4 → N +5 + N +3).
Iron oxide was dissolved in concentrated nitric acid. Sodium hydroxide solution was added to the resulting solution. The separated precipitate was separated and calcined. The resulting solid residue was fused with iron. Write the equations for the four reactions described.
The formula for iron scale is Fe 3 O 4.
When iron scale interacts with concentrated nitric acid, iron nitrate is formed and nitrogen oxide NO 2 is released:
Fe 3 O 4 + 10HNO 3 (conc.) → 3Fe (NO 3) 3 + NO 2 + 5H 2 O
When iron nitrate interacts with sodium hydroxide, a precipitate is formed - iron (III) hydroxide:
Fe (NO 3) 3 + 3NaOH → Fe (OH) 3 ↓ + 3NaNO 3
Fe (OH) 3 - amphoteric hydroxide, insoluble in water, decomposes on heating into iron (III) oxide and water:
2Fe (OH) 3 → Fe 2 O 3 + 3H 2 O
When iron (III) oxide is fused with iron, iron (II) oxide is formed:
Fe 2 O 3 + Fe → 3FeO
The sodium was burned in air. The resulting substance was treated with hydrogen chloride on heating. The resulting simple yellow-green substance, when heated, reacted with chromium (III) oxide in the presence of potassium hydroxide. When a solution of one of the formed salts was treated with barium chloride, a yellow precipitate formed. Write the equations for the four reactions described.
1) When sodium is burned in air, sodium peroxide is formed:
2Na + O 2 → Na 2 O 2
2) When sodium peroxide interacts with hydrogen chloride, Cl 2 gas is released when heated:
Na 2 O 2 + 4HCl → 2NaCl + Cl 2 + 2H 2 O
3) In an alkaline environment, chlorine reacts when heated with amphoteric chromium oxide to form chromate and potassium chloride:
Cr 2 O 3 + 3Cl 2 + 10KOH → 2K 2 CrO 4 + 6KCl + 5H 2 O
2Cr +3 -6e → 2Cr +6 | ... 3 - oxidation
Cl 2 + 2e → 2Cl - | ... 1 - recovery
4) A yellow precipitate (BaCrO 4) is formed by the interaction of potassium chromate and barium chloride:
K 2 CrO 4 + BaCl 2 → BaCrO 4 ↓ + 2KCl
Zinc was completely dissolved in concentrated potassium hydroxide solution. The resulting clear solution was evaporated and then calcined. The solid residue was dissolved in the required amount of hydrochloric acid. Ammonium sulfide was added to the resulting clear solution and a white precipitate was observed. Write the equations for the four reactions described.
1) Zinc reacts with potassium hydroxide to form potassium tetrahydroxozincate (Al and Be behave similarly):
2) Potassium tetrahydroxozincate after calcination loses water and turns into potassium zincate:
3) Potassium zincate, when interacting with hydrochloric acid, forms zinc chloride, potassium chloride and water:
4) Zinc chloride, as a result of interaction with ammonium sulfide, turns into insoluble zinc sulfide - a white precipitate:
Hydroiodic acid was neutralized with potassium bicarbonate. The resulting salt was reacted with a solution containing potassium dichromate and sulfuric acid. When the formed simple substance interacted with aluminum, a salt was obtained. This salt was dissolved in water and mixed with potassium sulfide solution, resulting in a precipitate and gas evolution. Write the equations for the four reactions described.
1) Hydroiodic acid is neutralized by the acidic salt of weak carbonic acid, as a result of which carbon dioxide is released and NaCl is formed:
HI + KHCO 3 → KI + CO 2 + H 2 O
2) Potassium iodide enters into a redox reaction with potassium dichromate in an acidic medium, while Cr +6 is reduced to Cr +3, I is oxidized to molecular I 2, which precipitates:
6KI + K 2 Cr 2 O 7 + 7H 2 SO 4 → Cr 2 (SO 4) 3 + 4K 2 SO 4 + 3I 2 ↓ + 7H 2 O
2Cr +6 + 6e → 2Cr +3 │ 1
2I - -2e → I 2 │ 3
3) When molecular iodine interacts with aluminum, aluminum iodide is formed:
2Al + 3I 2 → 2AlI 3
4) When aluminum iodide interacts with a solution of potassium sulfide, Al (OH) 3 precipitates and H 2 S is released. The formation of Al 2 S 3 does not occur due to the complete hydrolysis of the salt in an aqueous solution:
2AlI 3 + 3K 2 S + 6H 2 O → 2Al (OH) 3 ↓ + 6KI + 3H 2 S
Aluminum carbide was completely dissolved in hydrobromic acid. To the resulting solution was added a solution of potassium sulfite, while the formation of a white precipitate and the evolution of colorless gas were observed. The gas was absorbed with a solution of potassium dichromate in the presence of sulfuric acid. The formed chromium salt was isolated and added to the barium nitrate solution; precipitation was observed. Write the equations for the four reactions described.
1) When aluminum carbide is dissolved in hydrobromic acid, a salt is formed - aluminum bromide, and methane is released:
Al 4 C 3 + 12HBr → 4AlBr 3 + 3CH 4
2) When aluminum bromide interacts with a solution of potassium sulfite, Al (OH) 3 precipitates and sulfur dioxide - SO 2 is released:
2AlBr 3 + 3K 2 SO 3 + 3H 2 O → 2Al (OH) 3 ↓ + 6KBr + 3SO 2
3) Passing sulfur dioxide through an acidified solution of potassium dichromate, while Cr +6 is reduced to Cr +3, S +4 is oxidized to S +6:
3SO 2 + K 2 Cr 2 O 7 + H 2 SO 4 → Cr 2 (SO 4) 3 + K 2 SO 4 + H 2 O
2Cr +6 + 6e → 2Cr +3 │ 1
S +4 -2e → S +6 │ 3
4) When chromium (III) sulfate interacts with a solution of barium nitrate, chromium (III) nitrate is formed, and white barium sulfate precipitates:
Cr 2 (SO 4) 3 + 3Ba (NO 3) 2 → 3BaSO 4 ↓ + 2Cr (NO 3) 3
Aluminum powder was added to the sodium hydroxide solution. An excess of carbon dioxide was passed through the solution of the resulting substance. The formed precipitate was separated and calcined. The resulting product was fused with sodium carbonate. Write the equations for the four reactions described.
1) Aluminum, as well as beryllium and zinc, is capable of reacting both with aqueous solutions of alkalis and with anhydrous alkalis during fusion. When aluminum is treated with an aqueous solution of sodium hydroxide, sodium tetrahydroxoaluminate and hydrogen are formed:
2) When carbon dioxide is passed through an aqueous solution of sodium tetrahydroxoaluminate, crystalline aluminum hydroxide precipitates. Since, by condition, an excess of carbon dioxide is passed through the solution, not carbonate is formed, but sodium bicarbonate:
Na + CO 2 → Al (OH) 3 ↓ + NaHCO 3
3) Aluminum hydroxide is an insoluble metal hydroxide, therefore, when heated, it decomposes into the corresponding metal oxide and water:
4) Aluminum oxide, which is an amphoteric oxide, when fusion with carbonates displaces carbon dioxide from them with the formation of aluminates (not to be confused with tetrahydroxoaluminates!):
Aluminum reacted with sodium hydroxide solution. The evolved gas was passed over a heated copper (II) oxide powder. The resulting simple substance was dissolved by heating in concentrated sulfuric acid. The resulting salt was isolated and added to the potassium iodide solution. Write the equations for the four reactions described.
1) Aluminum (also beryllium and zinc) reacts both with aqueous solutions of alkalis and with anhydrous alkalis during fusion. When aluminum is treated with an aqueous solution of sodium hydroxide, sodium tetrahydroxoaluminate and hydrogen are formed:
2NaOH + 2Al + 6H 2 O → 2Na + 3H 2
2) When hydrogen is passed over a heated copper (II) oxide powder, Cu +2 is reduced to Cu 0: the color of the powder changes from black (CuO) to red (Cu):
3) Copper dissolves in concentrated sulfuric acid to form copper (II) sulfate. In addition, this produces sulfur dioxide:
4) When copper sulfate is added to a solution of potassium iodide, a redox reaction occurs: Cu +2 is reduced to Cu +1, I is oxidized to I 2 (molecular iodine precipitates):
CuSO 4 + 4KI → 2CuI + 2K 2 SO 4 + I 2 ↓
Conducted electrolysis of sodium chloride solution. Iron (III) chloride was added to the resulting solution. The formed precipitate was filtered off and calcined. The solid residue was dissolved in hydroiodic acid. Write the equations for the four reactions described.
1) Electrolysis of sodium chloride solution:
Cathode: 2H 2 O + 2e → H 2 + 2OH -
Anode: 2Cl - - 2e → Cl 2
Thus, as a result of its electrolysis, gaseous H 2 and Cl 2 are released from the sodium chloride solution, while Na + and OH - ions remain in the solution. In general terms, the equation is written as follows:
2H 2 O + 2NaCl → H 2 + 2NaOH + Cl 2
2) When iron (III) chloride is added to the alkali solution, an exchange reaction occurs, as a result of which Fe (OH) 3 precipitates:
3NaOH + FeCl 3 → Fe (OH) 3 ↓ + 3NaCl
3) When iron (III) hydroxide is calcined, iron (III) oxide and water are formed:
4) When iron (III) oxide is dissolved in hydroiodic acid, FeI 2 is formed, while I 2 precipitates:
Fe 2 O 3 + 6HI → 2FeI 2 + I 2 ↓ + 3H 2 O
2Fe +3 + 2e → 2Fe +2 │1
2I - - 2e → I 2 │1
Potassium chlorate was heated in the presence of a catalyst, while a colorless gas was evolved. By burning iron in an atmosphere of this gas, iron scale was obtained. It was dissolved in an excess of hydrochloric acid. To the resulting solution was added a solution containing sodium dichromate and hydrochloric acid.
1) When potassium chlorate is heated in the presence of a catalyst (MnO 2, Fe 2 O 3, CuO, etc.), potassium chloride is formed and oxygen is released:
2) When iron is burned in an oxygen atmosphere, iron scale is formed, the formula of which is Fe 3 O 4 (iron scale is a mixed oxide of Fe 2 O 3 and FeO):
3) When iron scale is dissolved in an excess of hydrochloric acid, a mixture of iron (II) and (III) chlorides is formed:
4) In the presence of a strong oxidizing agent - sodium dichromate, Fe +2 is oxidized to Fe +3:
6FeCl 2 + Na 2 Cr 2 O 7 + 14HCl → 6FeCl 3 + 2CrCl 3 + 2NaCl + 7H 2 O
Fe +2 - 1e → Fe +3 │6
2Cr +6 + 6e → 2Cr +3 │1
Ammonia was passed through hydrobromic acid. Silver nitrate solution was added to the resulting solution. The precipitate that formed was separated and heated with zinc powder. The metal formed during the reaction was acted upon with a concentrated solution of sulfuric acid, and gas with a pungent odor was released. Write the equations for the four reactions described.
1) When ammonia is passed through hydrobromic acid, ammonium bromide is formed (neutralization reaction):
NH 3 + HBr → NH 4 Br
2) When the solutions of ammonium bromide and silver nitrate are merged, an exchange reaction occurs between the two salts, as a result of which a light yellow precipitate - silver bromide:
NH 4 Br + AgNO 3 → AgBr ↓ + NH 4 NO 3
3) When silver bromide is heated with zinc powder, a substitution reaction occurs - silver is released:
2AgBr + Zn → 2Ag + ZnBr 2
4) When concentrated sulfuric acid acts on the metal, silver sulfate is formed and a gas with an unpleasant odor is released - sulfur dioxide:
2Ag + 2H 2 SO 4 (conc.) → Ag 2 SO 4 + SO 2 + 2H 2 O
2Ag 0 - 2e → 2Ag + │1
S +6 + 2e → S +4 │1
9S278S
Chromium (VI) oxide reacted with potassium hydroxide. The resulting substance was treated with sulfuric acid, and the orange salt was isolated from the resulting solution. This salt was treated with hydrobromic acid. The resulting simple substance reacted with hydrogen sulfide. Write the equations for the four reactions described.
1) Chromium (VI) oxide CrO 3 is an acidic oxide, therefore, it interacts with alkali to form a salt - potassium chromate:
CrO 3 + 2KOH → K 2 CrO 4 + H 2 O
2) Potassium chromate in an acidic medium is converted without changing the oxidation state of chromium into dichromate K 2 Cr 2 O 7 - an orange salt:
2K 2 CrO 4 + H 2 SO 4 → K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O
3) When treating potassium dichromate with hydrobromic acid, Cr +6 is reduced to Cr +3, while molecular bromine is released:
K 2 Cr 2 O 7 + 14HBr → 2CrBr 3 + 2KBr + 3Br 2 + 7H 2 O
2Cr +6 + 6e → 2Cr +3 │1
2Br - - 2e → Br 2 │3
4) Bromine, as a stronger oxidant, displaces sulfur from its hydrogen compound:
Br 2 + H 2 S → 2HBr + S ↓
Magnesium powder was heated under nitrogen atmosphere. When the resulting substance interacted with water, gas was released. The gas was passed through an aqueous solution of chromium (III) sulfate, resulting in the formation of a gray precipitate. The precipitate was separated and treated under heating with a solution containing hydrogen peroxide and potassium hydroxide. Write the equations for the four reactions described.
1) When magnesium powder is heated in a nitrogen atmosphere, magnesium nitride is formed:
2) Magnesium nitride is completely hydrolyzed to form magnesium hydroxide and ammonia:
Mg 3 N 2 + 6H 2 O → 3Mg (OH) 2 ↓ + 2NH 3
3) Ammonia has basic properties due to the presence of a lone electron pair at the nitrogen atom and, as a base, enters into an exchange reaction with chromium (III) sulfate, which results in a gray precipitate - Cr (OH) 3:
6NH 3. H 2 O + Cr 2 (SO 4) 3 → 2Cr (OH) 3 ↓ + 3 (NH 4) 2 SO 4
4) Hydrogen peroxide in an alkaline medium oxidizes Cr +3 to Cr +6, resulting in the formation of potassium chromate:
2Cr (OH) 3 + 3H 2 O 2 + 4KOH → 2K 2 CrO 4 + 8H 2 O
Cr +3 -3e → Cr +6 │2
2O - + 2e → 2O -2 │3
The interaction of aluminum oxide with nitric acid formed a salt. The salt was dried and calcined. The solid residue formed during calcination was subjected to electrolysis in molten cryolite. The metal obtained by electrolysis was heated with a concentrated solution containing potassium nitrate and potassium hydroxide, while a gas with a pungent odor was released. Write the equations for the four reactions described.
1) When amphoteric Al 2 O 3 interacts with nitric acid, a salt is formed - aluminum nitrate (exchange reaction):
Al 2 O 3 + 6HNO 3 → 2Al (NO 3) 3 + 3H 2 O
2) When aluminum nitrate is calcined, aluminum oxide is formed, and nitrogen dioxide and oxygen are also released (aluminum belongs to the group of metals (in the range of activity from alkaline earth to Cu, inclusive), the nitrates of which decompose to metal oxides, NO 2 and O 2):
3) Metallic aluminum is formed during the electrolysis of Al 2 O 3 in molten cryolite Na 2 AlF 6 at 960-970 o C.
Al 2 O 3 electrolysis scheme:
Dissociation of aluminum oxide proceeds in the melt:
Al 2 O 3 → Al 3+ + AlO 3 3-
K (-): Al 3+ + 3e → Al 0
A (+): 4AlO 3 3- - 12e → 2Al 2 O 3 + 3O 2
The overall equation of the process:
Liquid aluminum collects at the bottom of the cell.
4) When processing aluminum with a concentrated alkaline solution containing potassium nitrate, ammonia is released, and potassium tetrahydroxoaluminate is also formed (alkaline medium):
8Al + 5KOH + 3KNO 3 + 18H 2 O → 3NH 3 + 8K
Al 0 - 3e → Al +3 │8
N +5 + 8e → N -3 │3
8AAA8C
Some of the iron (II) sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. The interaction of the evolved gases resulted in the formation of a simple yellow substance. The resulting substance was heated with concentrated nitric acid, while a brown gas was evolved. Write the equations for the four reactions described.
1) When treating iron (II) sulfide with hydrochloric acid, iron (II) chloride is formed and hydrogen sulfide is released (exchange reaction):
FeS + 2HCl → FeCl 2 + H 2 S
2) When roasting iron (II) sulfide, iron is oxidized to the oxidation state +3 (Fe 2 O 3 is formed) and sulfur dioxide is released:
3) When two sulfur-containing compounds SO 2 and H 2 S interact, a redox reaction (coproportionation) occurs, as a result of which sulfur is released:
2H 2 S + SO 2 → 3S ↓ + 2H 2 O
S -2 - 2e → S 0 │2
S +4 + 4e → S 0 │1
4) When sulfur is heated with concentrated nitric acid, sulfuric acid and nitrogen dioxide are formed (redox reaction):
S + 6HNO 3 (conc.) → H 2 SO 4 + 6NO 2 + 2H 2 O
S 0 - 6e → S +6 │1
N +5 + e → N +4 │6
The gas obtained by treating calcium nitride with water was passed over a red-hot powder of copper (II) oxide. The resulting solid was dissolved in concentrated nitric acid, the solution was evaporated and the resulting solid was calcined. Write the equations for the four reactions described.
1) Calcium nitride reacts with water to form alkali and ammonia:
Ca 3 N 2 + 6H 2 O → 3Ca (OH) 2 + 2NH 3
2) Passing ammonia over a red-hot powder of copper (II) oxide, copper in the oxide is reduced to metallic, while nitrogen is released (hydrogen, coal, carbon monoxide, etc. are also used as reducing agents):
Cu +2 + 2e → Cu 0 │3
2N -3 - 6e → N 2 0 │1
3) Copper, located in the row of metal activities after hydrogen, interacts with concentrated nitric acid to form copper nitrate and nitrogen dioxide:
Cu + 4HNO 3 (conc.) → Cu (NO 3) 2 + 2NO 2 + 2H 2 O
Cu 0 - 2e → Cu +2 │1
N +5 + e → N +4 │2
4) When copper nitrate is calcined, copper oxide is formed, and nitrogen dioxide and oxygen are also released (copper belongs to the group of metals (in the range of activity from alkaline earth to Cu, inclusive), the nitrates of which decompose to metal oxides, NO 2 and O 2):
Silicon was burned in a chlorine atmosphere. The resulting chloride was treated with water. The precipitate that formed was calcined. Then fused with calcium phosphate and coal. Write the equations for the four reactions described.
1) Silicon react with chlorine at a temperature of 340-420 o C in a stream of argon to form silicon (IV) chloride:
2) Silicon (IV) chloride is completely hydrolyzed, while hydrochloric acid is formed, and silicic acid precipitates:
SiCl 4 + 3H 2 O → H 2 SiO 3 ↓ + 4HCl
3) When calcined, silicic acid decomposes to silicon oxide (IV) and water:
4) When silicon dioxide is fused with coal and calcium phosphate, a redox reaction occurs, as a result of which calcium silicate, phosphorus are formed, and carbon monoxide is also released:
C 0 - 2e → C +2 │10
4P +5 + 20e → P 4 0 │1
Note! This format of assignments is outdated, but nevertheless, assignments of this type deserve attention, since in fact they require writing the same equations that are found in the CMMs of the USE of the new format.
Substances are given: iron, iron scale, dilute hydrochloric acid and concentrated nitric acid. Write the equations of four possible reactions between all the proposed substances, without repeating pairs of reagents.
1) Hydrochloric acid reacts with iron, oxidizing it to the oxidation state +2, while hydrogen is released (substitution reaction):
Fe + 2HCl → FeCl 2 + H 2
2) Concentrated nitric acid passivates iron (i.e., a strong protective oxide film forms on its surface), however, under the influence of high temperature, iron is oxidized with concentrated nitric acid to an oxidation state of +3:
3) Formula of iron scale - Fe 3 O 4 (a mixture of iron oxides FeO and Fe 2 O 3). Fe 3 O 4 enters into an exchange reaction with hydrochloric acid, and a mixture of two chlorides of iron (II) and (III) is formed:
Fe 3 O 4 + 8HCl → 2FeCl 3 + FeCl 2 + 4H 2 O
4) In addition, iron scale enters into a redox reaction with concentrated nitric acid, while the Fe +2 contained in it is oxidized to Fe +3:
Fe 3 O 4 + 10HNO 3 (conc.) → 3Fe (NO 3) 3 + NO 2 + 5H 2 O
5) Iron scale and iron, when sintered, enter into a proportional reaction (the same chemical element acts as an oxidizing agent and a reducing agent):
Substances are given: phosphorus, chlorine, aqueous solutions of sulfuric acid and potassium hydroxide. Write the equations of four possible reactions between all the proposed substances, without repeating pairs of reagents.
1) Chlorine is a poisonous gas with high chemical activity, it reacts especially vigorously with red phosphorus. In an atmosphere of chlorine, phosphorus ignites spontaneously and burns with a weak greenish flame. Depending on the ratio of the reactants, phosphorus (III) chloride or phosphorus (V) chloride can be obtained:
2P (red) + 3Cl 2 → 2PCl 3
2P (red) + 5Cl 2 → 2PCl 5
Cl 2 + 2KOH → KCl + KClO + H 2 O
If chlorine is passed through a hot concentrated alkali solution, molecular chlorine disproportionates into Cl +5 and Cl -1, resulting in the formation of chlorate and chloride, respectively:
3) As a result of the interaction of aqueous solutions of alkali and sulfuric acid, an acidic or medium salt of sulfuric acid is formed (depending on the concentration of reagents):
KOH + H 2 SO 4 → KHSO 4 + H 2 O
2KOH + H 2 SO 4 → K 2 SO 4 + 2H 2 O (neutralization reaction)
4) Strong oxidants such as sulfuric acid convert phosphorus to phosphoric acid:
2P + 5H 2 SO 4 → 2H 3 PO 4 + 5SO 2 + 2H 2 O
Substances are given: nitric oxide (IV), copper, potassium hydroxide solution and concentrated sulfuric acid. Write the equations of four possible reactions between all the proposed substances, without repeating pairs of reagents.
1) Copper, located in the row of metal activities to the right of hydrogen, is capable of oxidizing with strong oxidizing acids (H 2 SO 4 (conc.), HNO 3, etc.):
Cu + 2H 2 SO 4 (conc.) → CuSO 4 + SO 2 + 2H 2 O
2) As a result of the interaction of the KOH solution with concentrated sulfuric acid, an acid salt is formed - potassium hydrogen sulfate:
KOH + H 2 SO 4 (conc.) → KHSO 4 + H 2 O
3) When passing brown gas, NO 2 N +4 disproportionates to N +5 and N +3, resulting in the formation of potassium nitrate and nitrite, respectively:
2NO 2 + 2KOH → KNO 3 + KNO 2 + H 2 O
4) When brown gas is passed through a concentrated solution of sulfuric acid, N +4 is oxidized to N +5 and sulfur dioxide is released:
2NO 2 + H 2 SO 4 (conc.) → 2HNO 3 + SO 2
Substances are given: chlorine, sodium hydrosulfide, potassium hydroxide (solution), iron. Write the equations of four possible reactions between all the proposed substances, without repeating pairs of reagents.
1) Chlorine, being a strong oxidizing agent, reacts with iron, oxidizing it to Fe +3:
2Fe + 3Cl 2 → 2FeCl 3
2) When chlorine is passed through a cold concentrated alkali solution, chloride and hypochlorite are formed (molecular chlorine disproportionates to Cl +1 and Cl -1):
2KOH + Cl 2 → KCl + KClO + H 2 O
If chlorine is passed through a hot concentrated alkali solution, molecular chlorine disproportionates into Cl +5 and Cl -1, resulting in the formation of chlorate and chloride, respectively:
3Cl 2 + 6KOH → 5KCl + KClO 3 + 3H 2 O
3) Chlorine, which has stronger oxidizing properties, is able to oxidize the sulfur included in the acid salt:
Cl 2 + NaHS → NaCl + HCl + S ↓
4) Acid salt - sodium hydrosulfide in an alkaline medium turns into sulfide:
2NaHS + 2KOH → K 2 S + Na 2 S + 2H 2 O
1 ... Sodium was burned in excess of oxygen, the resulting crystalline substance was placed in a glass tube and carbon dioxide was passed through it. The gas exiting the tube was collected and phosphorus was burned in its atmosphere. The resulting substance was neutralized with an excess of sodium hydroxide solution.
1) 2Na + O 2 = Na 2 O 2
2) 2Na 2 O 2 + 2CO 2 = 2Na 2 CO 3 + O 2
3) 4P + 5O 2 = 2P 2 O 5
4) P 2 O 5 + 6 NaOH = 2Na 3 PO 4 + 3H 2 O
2. Aluminum carbide was treated with hydrochloric acid. The released gas was burned, the combustion products were passed through lime water until a white precipitate was formed, further passing the combustion products into the resulting suspension led to the dissolution of the precipitate.
1) Al 4 C 3 + 12HCl = 3CH 4 + 4AlCl 3
2) CH 4 + 2O 2 = CO 2 + 2H 2 O
3) CO 2 + Ca (OH) 2 = CaCO 3 + H 2 O
4) CaCO 3 + H 2 O + CO 2 = Ca (HCO 3) 2
3. The pyrite was fired, and the resulting gas with a pungent odor was passed through hydrosulfuric acid. The formed yellowish precipitate was filtered off, dried, mixed with concentrated nitric acid and heated. The resulting solution gives a precipitate with barium nitrate.
1) 4FeS 2 + 11O 2 → 2Fe 2 O 3 + 8SO 2
2) SO 2 + 2H 2 S = 3S + 2H 2 O
3) S + 6HNO 3 = H 2 SO 4 + 6NO 2 + 2H 2 O
4) H 2 SO 4 + Ba (NO 3) 2 = BaSO 4 ↓ + 2 HNO 3
4 ... Copper was placed in concentrated nitric acid, the resulting salt was isolated from the solution, dried and calcined. The solid reaction product was mixed with copper shavings and calcined in an inert gas atmosphere. The resulting substance was dissolved in ammonia water.
1) Cu + 4HNO 3 = Cu (NO 3) 2 + 2NO 2 + 2H 2 O
2) 2Cu (NO 3) 2 = 2CuO + 4NO 2 + O 2
3) Cu + CuO = Cu 2 O
4) Cu 2 O + 4NH 3 + H 2 O = 2OH
5 ... Iron filings were dissolved in dilute sulfuric acid, the resulting solution was treated with an excess of sodium hydroxide solution. The formed precipitate was filtered and left in air until it acquired a brown color. The brown matter was calcined to constant weight.
1) Fe + H 2 SO 4 = FeSO 4 + H 2
2) FeSO 4 + 2NaOH = Fe (OH) 2 + Na 2 SO 4
3) 4Fe (OH) 2 + 2H 2 O + O 2 = 4Fe (OH) 3
4) 2Fe (OH) 3 = Fe 2 O 3 + 3H 2 O
6 ... Zinc sulphide was calcined. The resulting solid was completely reacted with the potassium hydroxide solution. Carbon dioxide was passed through the resulting solution until a precipitate formed. The precipitate was dissolved in hydrochloric acid.
1) 2ZnS + 3O 2 = 2ZnO + 2SO 2
2) ZnO + 2NaOH + H 2 O = Na 2
3 Na 2 + CO 2 = Na 2 CO 3 + H 2 O + Zn (OH) 2
4) Zn (OH) 2 + 2 HCl = ZnCl 2 + 2H 2 O
7. The gas released during the interaction of zinc with hydrochloric acid was mixed with chlorine and detonated. The resulting gaseous product was dissolved in water and acted on manganese dioxide. The resulting gas was passed through a hot potassium hydroxide solution.
1) Zn + 2HCl = ZnCl 2 + H 2
2) Cl 2 + H 2 = 2HCl
3) 4HCl + MnO 2 = MnCl 2 + 2H 2 O + Cl 2
4) 3Cl 2 + 6KOH = 5KCl + KClO 3 + 3H 2 O
8. Calcium phosphide was treated with hydrochloric acid. The released gas was burned in a closed vessel, the combustion product was completely neutralized with a potassium hydroxide solution. A solution of silver nitrate was added to the resulting solution.
1) Ca 3 P 2 + 6HCl = 3CaCl 2 + 2PH 3
2) PH 3 + 2O 2 = H 3 PO 4
3) H 3 PO 4 + 3KOH = K 3 PO 4 + 3H 2 O
4) K 3 PO 4 + 3AgNO 3 = 3KNO 3 + Ag 3 PO 4
9 ... Ammonium dichromate was decomposed by heating. The solid decomposition product was dissolved in sulfuric acid. Sodium hydroxide solution was added to the resulting solution until a precipitate formed. With further addition of sodium hydroxide to the precipitate, it dissolved.
1) (NH 4) 2 Cr 2 O 7 = Cr 2 O 3 + N 2 + 4H 2 O
2) Cr 2 O 3 + 3H 2 SO 4 = Cr 2 (SO 4) 3 + 3H 2 O
3) Cr 2 (SO 4) 3 + 6NaOH = 3Na 2 SO 4 + 2Cr (OH) 3
4) 2Cr (OH) 3 + 3NaOH = Na 3
10 ... Calcium orthophosphate was calcined with coal and river sand. The resulting white glowing in the dark substance was burned in a chlorine atmosphere. The product of this reaction was dissolved in excess potassium hydroxide. Barium hydroxide solution was added to the resulting mixture.
1) Ca 3 (PO 4) 2 + 5C + 3SiO 2 = 3CaSiO 3 + 5CO + 2P
2) 2P + 5Cl 2 = 2PCl 5
3) PCl 5 + 8KOH = K 3 PO 4 + 5KCl + 4H 2 O
4) 2K 3 PO 4 + 3Ba (OH) 2 = Ba 3 (PO 4) 2 + 6KOH
11. The aluminum powder was mixed with sulfur and heated. The resulting substance was placed in water. The resulting precipitate was divided into two parts. Hydrochloric acid was added to one part, and sodium hydroxide solution to the other until the precipitate was completely dissolved.
1) 2Al + 3S = Al 2 S 3
2) Al 2 S 3 + 6H 2 O = 2Al (OH) 3 + 3H 2 S
3) Al (OH) 3 + 3HCl = AlCl 3 + 3H 2 O
4) Al (OH) 3 + NaOH = Na
12 ... Silicon was placed in a solution of potassium hydroxide, after the end of the reaction, an excess of hydrochloric acid was added to the resulting solution. The formed precipitate was filtered off, dried and calcined. The solid product of the calcination reacts with hydrogen fluoride.
1) Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2
2) K 2 SiO 3 + 2HCl = 2KCl + H 2 SiO 3
3) H 2 SiO 3 = SiO 2 + H 2 O
4) SiO 2 + 4HF = SiF 4 + 2H 2 O
Tasks for independent solution.
1. As a result of the thermal decomposition of ammonium dichromate, a gas was obtained, which was passed over heated magnesium. The resulting substance was placed in water. The resulting gas was passed through freshly precipitated copper (II) hydroxide. Write down the equations for the reactions described.
2. To the solution obtained as a result of the interaction of sodium peroxide with water upon heating, a solution of hydrochloric acid was added until the end of the reaction. The solution of the formed salt was subjected to electrolysis with inert electrodes. The gas formed as a result of electrolysis at the anode was passed through a suspension of calcium hydroxide. Write down the equations for the reactions described.
3. The precipitate formed as a result of the interaction of a solution of iron (II) sulfate and sodium hydroxide was filtered off and calcined. The solid residue was completely dissolved in concentrated nitric acid. Copper shavings were added to the resulting solution. Write down the equations for the reactions described.
4. The gas obtained during the roasting of pyrite reacted with hydrogen sulfide. The resulting yellow substance was treated with concentrated nitric acid while heating. A solution of barium chloride was added to the resulting solution. Write down the equations for the reactions described.
5. The gas obtained by the interaction of iron filings with a solution of hydrochloric acid was passed over heated copper (II) oxide until the metal was completely reduced. The resulting metal was dissolved in concentrated nitric acid. The resulting solution was subjected to electrolysis with inert electrodes. Write down the equations for the reactions described.
6. The gas evolved at the anode during the electrolysis of mercury (II) nitrate was used for the catalytic oxidation of ammonia. The resulting colorless gas instantly reacted with atmospheric oxygen. The resulting brown gas was passed through barite water. Write down the equations for the reactions described.
7. Iodine was placed in a test tube with concentrated hot nitric acid. The evolved gas was passed through water in the presence of oxygen. Copper (II) hydroxide was added to the resulting solution. The resulting solution was evaporated and the dry solid residue was calcined. Write down the equations for the reactions described.
8. When the aluminum sulfate solution interacted with a potassium sulfide solution, a gas was released, which was passed through a solution of potassium hexahydroxoaluminate. The formed precipitate was filtered off, washed, dried and heated. The solid residue was fused with sodium hydroxide. Write down the equations for the reactions described.
9. Sulfur dioxide was passed through the sodium hydroxide solution until a medium salt was formed. An aqueous solution of potassium permanganate was added to the resulting solution. The formed precipitate was separated and acted on with hydrochloric acid. The evolved gas was passed through a cold potassium hydroxide solution. Write down the equations for the reactions described.
10. A mixture of silicon oxide (IV) and metallic magnesium was calcined. The simple substance obtained as a result of the reaction was treated with a concentrated solution of sodium hydroxide. The evolved gas was passed over heated sodium. The resulting substance was placed in water. Write down the equations for the reactions described.
Topic 7. Chemical properties and production of organic substances in tasks C3. Reactions that cause the greatest difficulty in schoolchildren, outside the scope of the school course.
To solve tasks C3, schoolchildren need to know the entire course of organic chemistry at a specialized level.
