"Redox Reactions" Elements and the World of Matter PPT (Application of Redox Reactions in Lesson 3)

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"Redox Reactions" Elements and the World of Matter PPT (Application of Redox Reactions in Lesson 3)

Part One: Literacy Goals

1. Through the study of the wide application of redox reactions in production and life, stimulate interest in learning chemistry and embody the core values ​​of chemical practicality and social responsibility.

2. By understanding the harm caused by some redox reactions in production and life, cultivate students' ability to dialectically analyze and understand things, and embody the core qualities of scientific inquiry and innovation.

3. Through learning, we will understand the close relationship between chemistry and production, life, and society, guide students to realize that science and technology can promote social development and progress, and embody the core qualities of scientific attitude and social responsibility.

Redox reaction PPT, part 2 content: knowledge foundation

1. Redox reactions and substance classification

A new perspective on understanding substance classification through learning redox reactions - studying the properties of substances from the perspective of oxidation and reduction.

2. In the reaction 10I-+2MnO_4^"-" +16H+ 5I2+2Mn2++8H2O, the oxidant is MnO_4^"-" and the reducing agent is I-. The reaction phenomenon is that the solution changes from purple to brown.

Redox Reaction PPT, Part 3: Preview of New Knowledge

1. Study the properties of matter

1. Properties of hydrogen peroxide

(1) Physical properties: colorless liquid, easily soluble in water.

(2) The oxidizing and reducing properties of H2O2

① By reacting with the acidic KMnO4 solution, the KMnO4 solution fades, proving that H2O2 has reducing properties;

② By reacting with KI solution and adding starch solution, the mixed solution turns blue, proving that H2O2 has oxidizing properties.

2. Determine whether a substance acts as an oxidant or reducing agent in a reaction

To determine whether a substance is an oxidant or a reducing agent in a redox reaction, it is necessary to analyze the relative strength of the reducing or oxidizing properties of the substances participating in the reaction. The oxidizing or reducing properties of a substance are determined by its ability to gain and lose electrons.

[Micro Thought 1] Why is H2O2 said to be a “green oxidant”?

Tip: The valence of the oxygen element in H2O2 is -1, and the valence can be increased or decreased. As an oxidant, its reduction product is water and will not cause pollution, so H2O2 is a "green oxidant".

2. Realize material transformation and obtain energy

1.Metal smelting methods

(1) Thermal reduction method

It is suitable for the smelting of most moderately active metals. Commonly used reducing agents include carbon, carbon monoxide, etc. For example, CO reduces Fe2O3 to obtain metallic iron:

(2)Metal replacement method

Using active metals as reducing agents, the target metal is reduced from its salt solution. For example, iron is used to replace copper from CuSO4 solution:

(3)Electrolysis method

Use an external power supply to provide electrons to reduce the valence of metal elements, thereby obtaining metal elements, such as electrolytic alumina to prepare metallic aluminum.

(4) Thermal decomposition method

Suitable for the smelting of inactive metals, such as heating and decomposing HgO to prepare metallic mercury:

2. Laboratory preparation of chlorine gas

(1) Preparation principle: 4HCl (concentrated) + MnO2 MnCl2 +Cl2↑+2H2O.

(2) The reaction of MnO2 and concentrated hydrochloric acid to prepare Cl2 is a redox reaction, with MnO2 as the oxidant and HCl as the reducing agent.

[Micro Thinking 2] Please discuss what factors should be considered when using chemical reactions to prepare new substances in the laboratory?

Tips: Mainly consider that the experimental operation is simple and easy, the phenomenon is obvious, the steps are as few as possible, and safety must be ensured.

Redox reaction PPT, part 4 content: exploration

The application of redox reactions in studying the properties of matter

Question exploration

1. Based on the knowledge of valence, analyze whether hydrogen peroxide has oxidizing or reducing properties?

Tip: The valence of O in H2O2 is -1, which is between -2 and 0. Therefore, it can be predicted that hydrogen peroxide has both oxidizing and reducing properties.

2. What is the basis for proving that hydrogen peroxide has oxidizing or reducing properties?

Tip: Use acidic KMnO4 solution to test that H2O2 has reducing properties; use KI solution and starch solution to test that H2O2 has oxidizing properties.

Knowledge induction

1. Chemical properties of hydrogen peroxide

(1) Oxidizing property - green oxidant:

H2O2+2KI+2HCl 2KCl+I2+2H2O

Or H2O2+2I-+2H+ I2+2H2O.

(2)Reducibility:

2KMnO4+5H2O2+3H2SO4 2MnSO4+K2SO4+5O2↑+8H2O.

(3)Instability:

2H2O2 O2↑ +2H2O or 2H2O2 2H2O+O2↑.

2. Design and implement experimental plans to explore the oxidizing or reducing properties of hydrogen peroxide

3. Main uses: green oxidant, bleach, disinfectant, medical hydrogen peroxide (about 3% or less) is a good disinfectant.

Methods to refine ideas for studying the oxidizing or reducing properties of substances

(1) Based on the possibility of the valence of the elements contained in the substance increasing or decreasing, it is predicted that the substance may have reducing or oxidizing properties. If the valence of the contained elements tends to increase, it means that the substance has reducing properties. On the contrary, if the valence of the contained elements tends to decrease, it means that the substance is oxidizing.

(2) If it is predicted that a certain substance is oxidizing, it is necessary to find another substance that is reducing, and test whether the two can undergo a redox reaction through experiments to verify the prediction. Correspondingly, if a substance is predicted to have reducing properties, it is necessary to find another substance with oxidizing properties and verify the prediction through experiments.

Analysis of typical cases

Example 1H2O2 is a green redox reagent and is widely used in chemical research.

(1) The experiment proves that under the catalysis of Fe2(SO4)3, H2O2 can decompose. Write the chemical equation of the H2O2 decomposition reaction in the process and use a double line bridge to indicate the direction and number of electron transfer: _______________________.

(2) In the experiment of "Iodine extraction from kelp", the ionic equation of iodine element obtained from acidic H2O2 solution is _______________.

Redox Reaction PPT, Part 5: In-class Testing

1. Which of the following groups of metals is most suitable for reducing them from compounds using H2 or CO ()

A.Ca, Mg B.Al, Fe C.Fe, Cu D.Hg, Ag

Answer:C

Analysis: The preparation method of moderately active metals is thermal reduction. In the order of metal activity, more active metals such as K→Al are generally smelted by electrolysis, less active metals such as Zn→Cu are generally smelted by thermal reduction, and metals such as Hg and Ag can be smelted by thermal decomposition. Of course, these metals There are no strict boundaries for smelting methods. For example, Cu can be smelted by thermal reduction method or electrolytic method.

2. To collect relatively pure Cl2, it is best to use ()

A. Upward air exhaust method B. Downward air exhaust method

C. Drainage method D. Drainage method of saturated salt water

Answer:A

Analysis: To collect relatively pure Cl2, it is best to use the upward air exhaust method.

3. Among the following commonly used desiccants, the one that cannot dry chlorine gas is ()

A. Concentrated sulfuric acid B. Phosphorus pentoxide

C. Soda lime D. Calcium chloride

Answer:C

Analysis: The composition of soda lime is a mixture of sodium hydroxide and calcium oxide, which will absorb chlorine, so soda lime cannot be used to dry chlorine.

4. A group of substances that can all reduce Fe2O3 to Fe is ()

A.CO, O2, H2 B.CO, H2, C

C.CO2, H2O, O2 D.CO2, O2, C

Answer:B

Analysis: CO, H2, C and other reducing agents can reduce Fe2O3 to Fe.

5. The following operations are performed when preparing chlorine gas in the laboratory. The correct sequence of operations is ()

①Connect the device and check the air tightness; ②Heat slowly; ③Add manganese dioxide powder; ④Add concentrated hydrochloric acid; ⑤Absorb excess chlorine gas with sodium hydroxide solution; ⑥Collect chlorine gas by upward exhaust air method.

A.①②③④⑤⑥ B.③④②①⑥⑤

C.①④③②⑥⑤ D.①③④②⑥⑤

Answer:D

Analysis: When making Cl2 in the laboratory, first connect the device, then check the air tightness of the device, add reagents for reaction, then collect the gas, and perform exhaust gas treatment at the same time.

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Update Time: 2024-10-02

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