"Conversion of Sulfur" Nature and Transformation of Substances PPT (Lesson 2: Sulfuric Acid Rain and Its Prevention and Control)

Description

"Conversion of Sulfur" Nature and Transformation of Substances PPT (Lesson 2: Sulfuric Acid Rain and Its Prevention and Control)

Part One: Literacy Goals

1. Through the mutual transformation between sulfur elements in different valence states, understand the properties of elemental sulfur, sulfur dioxide, and concentrated sulfuric acid, and understand the transformation between them from a combined macro and micro perspective.

2. Be able to master the properties of sulfuric acid and typical experimental phenomena through experimental exploration and communication and discussion, and be able to write major chemical equations and ionic equations. Ability to proactively communicate and gradually enhance awareness of scientific inquiry and innovation.

3. Be able to study the properties of substances from the two perspectives of substance category and element valence state, know the application of sulfur-containing substances in production and life, know acid rain and its prevention and control methods, and improve scientific attitude and social responsibility.

PPT on the transformation of sulfur, part 2: independent preview before class

Knowledge foundation

1. The common chemical valences of sulfur are -2, 0, +4, and +6. Elemental sulfur has both oxidizing and reducing properties. For example, in the reaction S+O2 SO2, S shows reducing properties, in S+Fe FeS, S shows oxidizing properties, 3S+6NaOH Na2SO3+2Na2S+3H2O, S shows both oxidizing and reducing properties.

2. SO2 is oxidized to obtain SO32SO2+O2 2SO3. SO3 reacts with water to obtain sulfuric acid SO3+H2O H2SO4. Sulfuric acid has acid properties.

Preview of new knowledge

1. Study the transformation of sulfur elements in different valence states in the laboratory

2. Sulfuric acid

1.Physical properties

Pure sulfuric acid is a colorless, viscous, oily liquid with a high boiling point and difficult to evaporate. The mass fraction of commonly used concentrated sulfuric acid is 98.3%, and its density is higher than that of water. Concentrated sulfuric acid releases a lot of heat when dissolved in water.

2. Characteristics of concentrated sulfuric acid

Concentrated sulfuric acid has three major properties: water absorption, dehydration and strong oxidation.

(1) The water absorption of concentrated sulfuric acid: The water absorption of concentrated sulfuric acid refers to the absorption of free H2O molecules or crystal water in the substance itself. For example, using concentrated sulfuric acid as a desiccant reflects its water absorption.

(2) Dehydration of concentrated sulfuric acid: Concentrated sulfuric acid can remove hydrogen and oxygen from some organic matter according to the composition of H2O (hydrogen atom: oxygen atom = 2:1).

For example, concentrated sulfuric acid can turn matchsticks and paper black, which reflects its dehydration property.

(3) The strong oxidizing property of concentrated sulfuric acid: reacts with inactive metals or non-metals.

At normal temperature, cold concentrated sulfuric acid can form a dense oxide protective film on the surface of Fe and Al, preventing the internal metal from reacting with H2SO4. This phenomenon is called passivation.

3. Industrial production of sulfuric acid, contact with legal sulfuric acid production

(1) Raw materials: sulfur or pyrite (FeS2), air, 98.3% concentrated sulfuric acid.

(2) Main chemical reactions: S+O2 SO2 or 4FeS2+11O2 2Fe2O3+8SO2, 2SO2+O2 2SO3, SO3+H2O H2SO4.

3. Acid rain and its prevention and control

1. The formation of acid rain

Sulfur oxides are the main substances that form acid rain. The SO2 emitted by the combustion of sulfur-containing fuels forms acid mist under the combined action of oxygen and water vapor, which becomes acid rain when rain falls. The acid rain formed in this way is also called sulfuric acid rain. The main reactions are as follows:

2. Acid rain is very harmful. It can directly destroy forests, grasslands and crops, increase soil acidity, acidify lakes, and accelerate the corrosion of buildings, bridges, industrial equipment, etc.

3. Prevention and control of acid rain

(1) Strictly stipulate emission standards for pollutants.

(2) Develop clean energy.

[Micro Thought 1] Concentrated sulfuric acid can turn blue bile vitriol into white. Does this process reflect the dehydration or water absorption of concentrated sulfuric acid?

Tip: It reflects water absorption. The water absorption of concentrated sulfuric acid means that concentrated sulfuric acid absorbs ready-made water molecules (such as water molecules in gases and liquids, absorbs crystal water in solids, etc.); while dehydration means that concentrated sulfuric acid can absorb organic matter. The hydrogen atoms and oxygen atoms in the water were released in a ratio of 2:1, and H and O did not originally exist in the form of water molecules.

[Micro Thought 2] Is precipitation with a pH less than 7 acid rain?

Tip: Not necessarily. Normal rainwater has a pH of 5.6 due to dissolved CO2. Precipitation with a pH less than 5.6 is called acid rain. After the collected acid rain samples are left for a period of time, the acidity will increase because part of the H2SO3 is converted into H2SO4.

Autonomous testing

1. Which of the following statements about concentrated sulfuric acid is correct ()

A. Concentrated sulfuric acid is water-absorbent and can carbonize sucrose.

B. Concentrated sulfuric acid can quickly react with copper sheets at room temperature to release sulfur dioxide gas.

C. Concentrated sulfuric acid is a desiccant that can dry ammonia, hydrogen and other gases

D. Concentrated sulfuric acid can passivate metals such as iron and aluminum at room temperature.

Answer:D

Analysis: Concentrated sulfuric acid carbonizes sucrose, which reflects dehydration rather than water absorption. The essential difference between dehydration and water absorption depends on whether the two elements hydrogen and oxygen exist in the form of H2O in the original substance. The reaction between concentrated sulfuric acid and copper needs to be carried out under heating conditions. As a desiccant, concentrated sulfuric acid cannot dry alkaline and strongly reducing gases. Ammonia cannot be dried with concentrated sulfuric acid but hydrogen can. Concentrated sulfuric acid must be used to passivate iron and aluminum at room temperature.

2. Judge whether it is right or wrong (mark “√” if it is correct and “×” if it is wrong).

(1) Use dilute sulfuric acid to clean the scale in the boiler. ()

(2) Use BaCl2 solution to identify SO42- and SO32-. ()

(3) Concentrated sulfuric acid has strong oxidizing properties, so concentrated sulfuric acid can be used to dry H2 and CO. ()

(4) Concentrated sulfuric acid turns blue vitriol (CuSO4·5H2O) into white powder, which reflects the strong oxidizing property of concentrated sulfuric acid. ()

(5) When 50 mL of 18.4 mol·L-1 concentrated sulfuric acid reacts with sufficient copper, the number of SO2 molecules generated is 0.46NA. ()

(6) Add acidified Ba(NO3)2 solution dropwise to the solution and a white precipitate will appear, indicating that there must be SO42- in the solution. ()

Answer: (1)× (2)× (3)× (4)× (5)× (6)×

PPT on the transformation of sulfur, part three: classroom exploration and learning

The strong oxidizing property of concentrated sulfuric acid and the test of ____

Question exploration

When concentrated sulfuric acid reacts with sufficient copper under heating conditions, what is the relationship between the reduced sulfuric acid and the total amount of sulfuric acid?

Tip: When concentrated sulfuric acid reacts with copper, it can be obtained from the chemical equation 2H2SO4 (concentrated) + Cu CuSO4 + SO2↑ + 2H2O. The reduced sulfuric acid accounts for one-half of the reacted sulfuric acid, but when the amount of copper is sufficient, as the reaction As the process proceeds, the concentration of sulfuric acid becomes smaller, and dilute sulfuric acid can no longer react with copper. Therefore, the reduced sulfuric acid is less than half of the total amount of sulfuric acid.

Knowledge induction

1. Strong oxidizing property of concentrated sulfuric acid

(1) Passivation of Fe and Al

At normal temperature, when Fe and Al encounter concentrated sulfuric acid, they will react to form a dense oxide film and cause "passivation".

(2) React with active metal before hydrogen

Zn+2H2SO4(concentrated) === ZnSO4+SO2↑+2H2O.

Rules: ① Concentrated sulfuric acid shows both oxidizing and acidic properties; ② After concentrated sulfuric acid becomes dilute, the reaction Zn+H2SO4 === ZnSO4+H2↑ occurs.

(3) React with inactive metals after hydrogen (except Au and Pt)

Rules: ① The reaction needs to be heated, otherwise there will be no reaction; ② The oxidation product is sulfate, the metal is high in price, and the reduction product is SO2; ③ Concentrated sulfuric acid shows both oxidizing and acidic properties; ④ As the reaction proceeds, the sulfuric acid concentration becomes smaller. When it becomes dilute sulfuric acid, the reaction will stop.

(4) React with non-metals

Rules: ① The reaction requires heating, otherwise there will be no reaction; ② The oxidation product is an oxygen acid or a non-metal oxide; the reduction product is SO2; ③ Concentrated sulfuric acid only shows oxidizing properties; ④ As the reaction proceeds, the sulfuric acid concentration becomes smaller and becomes dilute sulfuric acid The reaction stops; ⑤ H2, N2, O2, Si, Cl2, F2, Br2, etc. cannot be oxidized.

2.②CO_3^2"-", SO_3^2"-", PO_4^3"-" Interference: Inspection

(1)Correct operation

(2) Interference from impurity ions

①Ag+interference:

Acidification with hydrochloric acid can prevent Ag+ interference, because Ag++Cl-AgCl↓.

Because BaCO3, BaSO3, and Ba3(PO4)2 are also white precipitates. The difference from the white precipitation of BaSO4 is that these precipitates can be dissolved in strong acids (such as BaCO3+2H+ === H2O+CO2↑+Ba2+). Therefore, when testing __, it must be acidified with acid (usually hydrochloric acid is used instead of HNO3).

(3)Selection of barium salt

PPT on the transformation of sulfur, part 4: on-site testing

1. Which of the following descriptions of concentrated sulfuric acid is correct ()

A. At room temperature, concentrated sulfuric acid does not react with iron or aluminum.

B. Concentrated sulfuric acid has water absorption, so it can carbonize sucrose.

C. Concentrated sulfuric acid can be used as a desiccant for H2, NH3 and other gases to show dehydration.

D. Concentrated sulfuric acid reacts with copper sheets when heated, showing acidity and oxidation.

Answer:D

Analysis: Concentrated sulfuric acid passivates iron and aluminum at room temperature. It is the strong oxidizing property of concentrated sulfuric acid that forms a thin layer of dense oxide film on the surface of iron and aluminum to prevent the reaction from proceeding. Item A is wrong; concentrated sulfuric acid carbonizes sucrose, which reflects its Dehydration, item B is wrong; concentrated sulfuric acid cannot dry NH3, and concentrated sulfuric acid can be used as a desiccant for H2 to reflect its water absorption. Item C is wrong; when concentrated sulfuric acid reacts with copper sheets to produce copper sulfate, it is acidic, and sulfur dioxide is generated to show oxidation. , item D is correct.

2. Which of the following statements about environmental pollution is correct ()

A. Carbon dioxide can cause the greenhouse effect and is an atmospheric pollutant.

B. Acidic rainwater is called acid rain

C. Adding an appropriate amount of limestone when burning coal can reduce the amount of SO2 in the exhaust gas.

D. Acid rain will only make natural water acidic, but will not corrode buildings.

Answer:C

Analysis: The greenhouse effect mainly refers to the formation of the greenhouse effect due to human emissions of large amounts of carbon dioxide and other gases into the atmosphere, which enhances the absorption of infrared rays by the atmosphere, prevents the heat from the earth's surface from dissipating outward, and causes the temperature of the earth's surface to rise. However, carbon dioxide is not included in the atmosphere. pollutants, so item A is wrong; the pH of acid rain is less than 5.6, which is caused by a large amount of sulfur dioxide or nitrogen oxides in the air, so item B is wrong; when burning coal, add an appropriate amount of limestone, and the limestone decomposes under high temperatures to produce calcium oxide, which can be combined with Sulfur dioxide and oxygen react to form calcium sulfate, which can greatly reduce the amount of SO2 in the exhaust gas, so item C is correct; acid rain can also corrode buildings, so item D is wrong.

3. In the experimental device as shown in the figure, after a period of time after the experiment started, the description of the phenomenon seen is incorrect ()

A. ① The apple pieces will become shriveled

B. ② There are “white spots” on the surface of mesogallite crystals

C. ③ Crystals precipitated in small and medium test tubes

D.④The medium pH test paper turns red

Answer:D

Analysis: Concentrated sulfuric acid is water-absorbent, so the water in the apple pieces, the crystal water of the bile alum crystals, and the water in the saturated potassium nitrate solution will be absorbed. Items A, B, and C are all correct; the pH test paper will be dehydrated in concentrated sulfuric acid. Carbonization, strain black, item D error.

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