"Redox Reaction" PPT teaching courseware

Description

"Redox Reaction" PPT teaching courseware

Part One: Learning Objectives

1. Enable students to understand oxidation-reduction reactions and understand the nature of oxidation-reduction reactions from the perspective of the increase and decrease of chemical valence.

2. Understand the relationship between redox reactions and the four basic types.

3. Master the basic concepts of oxidation reaction, reduction reaction, redox reaction, oxidizing agent, reducing agent, etc.

4. Understand common oxidizing agents and reducing agents.

Redox reaction PPT, part 2 content: 1. Redox reaction

1. Concept

(1) The reaction in which oxygen atoms are gained is called an oxidation reaction, the reaction in which oxygen atoms are lost is called a reduction reaction, and the reaction in which oxygen atoms are gained or lost is called a redox reaction.

(2) The reaction in which the valence of elements contained in a substance increases is called an oxidation reaction, the reaction in which the valence of elements contained in a substance decreases is called a reduction reaction, and any chemical reaction in which the valence of elements increases or decreases is called an oxidation-reduction reaction.

(3) The reaction in which atoms of an element lose electrons is called an oxidation reaction, the reaction in which atoms of an element gain electrons is called a reduction reaction, and the reaction in which electrons are converted (gained, lost or shifted) is called an oxidation-reduction reaction.

2.Characteristics

A change in the valence of one or several elements.

3. Substance

The essence of a redox reaction is the transfer of electrons (i.e., the gain, loss, or shift of electrons).

4. Oxidation-reduction reaction and changes in valence

Due to the gain and loss of electrons (or electron pair deviation) in redox reactions, the valence of elements increases and decreases. To determine whether a reaction is a redox reaction, analyzing the valence of elements is the basis and prerequisite.

1) Memorize the main chemical combination prices (highest price and lowest price) of common elements.

(1) Metal elements have no negative valence, and their lowest price is 0.

Highest price:

(2) Non-metallic elements have negative valence, and most of them also have positive valence.

H C N O S Cl F

Minimum:-1 -4 -3 -2 -2 -1 -1

Maximum: +1 +4 +5 0 +6 +7 0

(3) Judgment of the valence of elements in a compound: from general to special. For example: H2O2. Since H is less non-metallic than O, H can only be positive and O is negative, so it is inferred that H2+1O2-1. Another example :K2MnO4, obviously K is +1 valence, O is -2 valence, it is inferred that Mn is +6 valence.

2. The relationship between electron transfer (gain, loss or shift) and the valence of elements in the redox reaction is as shown in the figure.

Redox Reaction PPT, Part 3: 2. Oxidizing Agents and Reducing Agents

1. Concept of oxidizing agent and reducing agent

(1) The oxidizing agent is a substance that obtains electrons (or electron pair bias). During the reaction, the valence of an element contained in the substance is reduced. The oxidizing agent has oxidizing properties and is reduced during the reaction. A reduction reaction occurs, and the obtained product is a reduction reaction. product.

(2) The reducing agent is a substance that loses electrons (or electron pairs are deviated). During the reaction, the valence of an element contained in the substance increases. The reducing agent has reducing properties and is oxidized during the reaction. An oxidation reaction occurs, and the obtained The product is an oxidation product.

2. Common oxidizing agents and reducing agents

(1) Common oxidants

①Some non-metallic elements: such as O2, Cl2, etc.

②Compounds containing high valence elements: such as concentrated sulfuric acid, HNO3, KMnO4, FeCl3, etc.

(2) Common reducing agents

①Active metal elements, such as Al, Zn, Fe, etc.

②Some non-metallic elements, such as C, H2, etc.

③Some non-metal oxides, such as CO, etc.

Intriguing inquiry: Oxidants have oxidizing properties and reducing agents have reducing properties. Can redox reactions definitely occur between common oxidizing agents and reducing agents?

Tip: For the redox reaction to occur, both an oxidizing agent and a reducing agent must be present, as well as certain conditions. Not all redox reactions can occur between any oxidizing agent and reducing agent.

For example: H2 and CO are commonly used reducing agents, and concentrated sulfuric acid is a commonly used oxidant. However, concentrated sulfuric acid is often used to dry H2 and CO in the laboratory. Obviously H2 and CO cannot be oxidized by concentrated sulfuric acid, so attention should be paid to analyzing whether a certain substance is an oxidant. It is still a reducing agent and cannot be separated from the specific reaction.

Redox reaction PPT, part 4 content: 3. The rules of oxidation-reduction reaction

1.Conservation law

(1) Law of conservation of mass: In chemical reactions, the type and number of element atoms remain unchanged before and after the reaction. This law is no exception in redox reactions.

(2) Law of electron conservation: In any redox reaction, the total number of electrons gained by the oxidizing agent is equal to the total number of electrons lost by the reducing agent, and the total number of increases and decreases in valence is equal.

For a reaction that is both a redox reaction and an ionic reaction, the total number of charges is equal.

2) Valence law

The valence state of an element in a substance determines its oxidizing or reducing properties. Generally speaking, an element in its highest valence state has only oxidizing properties (such as KMnO4, HNO3, etc.); an element in its lowest valence state has only reducing properties. (Such as S2-､I-, etc.); the element is in an intermediate valence state and has both oxidizing and reducing properties.

3. The law of “strong first, weak later”

When an oxidizing agent (or reducing agent) meets multiple reducing agents (or oxidizing agents), it always reacts with the reducing agent (or oxidizing agent) with strong reducing (or oxidizing) properties first.

For example, if excess dilute sulfuric acid is added to a mixture composed of Zn and Fe, due to the reducing nature of Zn>Fe.

First: Zn+H2SO4=ZnSO4+H2↑

After:Fe+H2SO4=FeSO4+H2↑

Redox Reaction PPT, Part 5: 4. Redox Reactions in Production and Life

metal smelting

plating

combustion of fuel

Photosynthesis of green plants

spontaneous combustion of flammable substances

food spoilage

corrosion of steel

Knowledge point 1: Judgment of redox reactions

Example 1 Analyze the following chemical reactions from the perspective of the increase and decrease of element valence. Among them, the ones that are not oxidation-reduction reactions are ( )

A.Mg+2HCl=MgCl2+H2↑

[Analysis] The valence of the magnesium element in A increases from 0 to +2, and the valence of the hydrogen element drops from +1 to 0; the valence of the hydrogen in B increases from 0 to +1, and the chlorine element The valence of the element in C dropped from 0 to -1; the valence of the hydrogen element in C increased from 0 to +1, and the valence of copper dropped from +2 to 0; in D, there was no change in the valence of the elements. So D is not a redox reaction.

Knowledge Point 2: The relationship between redox reactions and the four basic types

Example 2 The schematic diagram that can correctly represent the relationship between the four basic types of reactions and redox reactions is ( )

〔Analysis〕 The four basic reaction types are a formal division of reactions. Redox reactions and non-redox reactions are divided according to the nature of the reaction. According to the definition of displacement reaction, compounds are generated from simple substances and simple substances are generated from compounds. If there is a change in the valence of elements, it must be a redox reaction. The metathesis reaction is only the exchange of components between compounds. There must be no change in the valence of elements, and it must not be a redox reaction. The forms of combination reactions and decomposition reactions may overlap with redox reactions, and some are oxidation reactions. Reduction reactions, some are not oxidation-reduction reactions.

Knowledge point three: Judgment of basic concepts in redox reactions

Example 3 Calcium hydride can be used as a hydrogen generating agent. The chemical equation of the reaction is: CaH2+2H2O=Ca(OH)2+2H2↑. Which of the following statements is incorrect ( )

A.CaH2 is both an oxidizing agent and a reducing agent

B.H2 is both an oxidation product and a reduction product

C.CaH2 is a reducing agent and H2O is an oxidizing agent

D. The mass ratio of oxidation products to reduction products is 1:1

[Analysis] The key to this question is to analytically determine that the valence of the hydrogen element in CaH2 is -1. Only the valence of the hydrogen element changed during the reaction, and the valences of the other elements did not change. The hydrogen element is distributed in each substance before and after the reaction, At this time, you should first find out the unchanged part. The hydrogen of the product Ca(OH)2 is +1 valence. These two hydrogen atoms must come from H2O molecules, and there are a total of 4 +1 valence hydrogen atoms in H2O. Obviously, there are 4 +1 valence hydrogen atoms in H2O. Another part of the hydrogen must be reduced with electrons. The H2 molecule is generated by the oxidation of the -1-valent H element in CaH2 and the reduction of part of the +1-valent H element in H2O. Therefore, it can be concluded that option B in the question is the product Analysis, option C is the analysis of the reactants, both are correct, so it can be seen that option A is incorrect, option D is the quantitative analysis of the product, which is also correct.

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For more information about the "Redox Reaction" PPT courseware, please click the Redox Reaction PPT tab.

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Update Time: 2024-07-08

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