"Calculation and Balancing of Redox Reactions" Substances and Their Changes PPT

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"Calculation and Balancing of Redox Reactions" Substances and Their Changes PPT

Part One: Knowledge and Ability

1. Application of conservation method in calculation of redox reactions

1. The calculation of redox reactions mainly includes finding the ratio of the number or mass of oxidant to reducing agent, calculating the amount of oxidizing agent or reducing agent participating in the reaction, determining the valence change of an element before and after the reaction or the chemical formula of the substance, etc. The key to its calculation is based on the fact that the total number of electrons gained by the oxidizing agent is equal to the total number of electrons lost by the reducing agent (i.e., conservation of electrons gained and lost).

2. Steps to solve the electron conservation problem: First find out the number of oxidants, reducing agents and the amount of electrons gained and lost by each oxidant and reducing agent, and then formulate an equation based on electron conservation: Number of oxidants × number of electrons gained by each oxidant = reducing agent The number of electrons × the number of electrons lost by each reducing agent. Using this equation to solve redox reaction calculation problems can make difficult problems easy and complex problems simple.

2. Balancing the redox reaction equation

1. Basic principles for balancing redox reaction equations

2. Balancing steps for redox reaction equations

Calculation and balancing of redox reactions PPT, Part 2: Typical example navigation

[Typical Example 1] It is known that the following reaction can occur in an alkaline solution: 2M(OH)3+10OH-+3Cl2===2MOn-4+6Cl-+8H2O, then the valence of M in MOn-4 is ()

A. +4B. +5

C. +6 D. +7

[Typical Example 2] Balance the following two reactions (please also fill in the stoichiometric number is 1)

(1)________H2O +________Cl2 +______SO2===______H2SO4 +______HCl.

(2)________KMnO4＋________HCl===________KCl + ________MnCl2 + ________Cl2↑＋________H2O.

[ Analysis The total number of increases and decreases in chemical valence is equal; therefore, the stoichiometric number in front of Cl2 is 1, and the stoichiometric number in front of SO2 is 1. Then balance the stoichiometric numbers of other substances according to atomic conservation, and the correct one is 2H2O + Cl2 + SO2===H2SO4 + 2HCl; (2) According to the rule that the total number of increases and decreases in the valence of elements in the redox reaction is equal, balance is carried out: KMnO4→MnCl2, the valence of the manganese element decreases by 5 valences; 2HCl→Cl2, the valence of the chlorine element increases by 2 valences, and according to the rule that the total number of increases and decreases in the valence of the elements is equal: the stoichiometry in front of KMnO4 The number is 2, and the stoichiometric number in front of Cl2 is 5; finally, the stoichiometric numbers of other substances are balanced according to atomic conservation, and the correct one is 2KMnO4+16HCl===2KCl+2MnCl2+5Cl2↑+8H2O.

Calculation and balancing of redox reactions PPT, Part 3: Methods and skills

Basic skills for balancing redox reactions

(1) Calibration from the left for total changes: If the valence of an element in the oxidizing agent or reducing agent is completely changed, the balance is usually started from the reactants on the left.

(2) Calibration of self-changes from the right: autoredox reactions (including decomposition and disproportionation) are generally balanced from the right.

(3) Missing term balancing method: First balance the number of gained and lost electrons, and then observe the charges on both sides. If the reactant side lacks positive charge, H+ is usually added, and water is added to the product side; if the reactant side lacks negative charge, OH- is generally added, and water is added to the product side, and then the charges on both sides are balanced.

(4) When there are multiple missing terms in the equation, the oxidant, reducing agent, oxidation product, and reduction product should be identified according to the change in valence.

Calculation and balancing of redox reactions PPT, Part 4: Experience training

1. Potassium permanganate solution can react with ferrous sulfate under acidic conditions. The chemical equation is as follows (unbalanced): ________KMnO4 + ________FeSO4 + ________H2SO4 = = ________K2SO4 + _____________MnSO4 + ________Fe2(SO4)3 + ________H2O. Which of the following statements is correct ()

A. MnO-4 is the oxidant, Fe3+ is the reduction product

B． Fe2+ ​​is more reducible than Mn2+

C. Take the reaction solution and add KSCN solution. You can observe the formation of red precipitate.

D． When 4 water molecules are generated, 10 electrons are transferred

2. Balance the following chemical reactions

(1)________HCl(concentrated)+________MnO2=====△________Cl2↑＋________MnCl2＋________H2O.

(2)________Cu＋________HNO3(dilute)===________Cu(NO3)2+________NO↑＋________H2O.

(3)________S＋________KOH===________K2S＋________K2SO3＋________H2O.

(4)________ClO-+________Fe(OH)3+________===________Cl-+________FeO2-4+________H2O.

[ Analysis topic.

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Update Time: 2024-08-02

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