The oxidation number of an element in an element is zero

In neutral molecules, the algebraic sum of the oxides of each element is zero.

Except for peroxides, superoxides, etc., the oxidation number of oxygen is generally -2

The oxidation number of hydrogen in compounds is generally 1, only in active metal hydrides The oxidation number of hydrogen is -1

The oxidation numbers of alkali metals and alkaline earth metals in compounds are 1 and 2 respectively; The oxidation number of fluorine is -1. Other halogens except oxygen-containing compounds and electrostatic Except for the more negative halogens that form halogen compounds, they are generally -1

In a redox reaction, the reducing agent provides electrons, oxidizing agent acquires electrons, electronic Gains and losses occur simultaneously

Oxidizing agent and reducing agent are the oxidation of the same substance reduction reaction, called autoredox reaction

In an autoredox reaction, the oxidation number increases and What is reduced is the same element in the same substance. This A redox-like reaction is called a disproportionation reaction.

In a redox reaction, the gain and loss of electrons occur simultaneously. Similar to proton transfer in the acid-base conjugation relationship of acid-base reactions, The conjugation relationship between the oxidizing agent and the reducing agent involves electron transfer.

Write the chemical formulas of the reactants and products.

Mark the change in the oxidation number of the element and find the increase or decrease in the oxidation number.

Multiply the corresponding coefficients before the chemical formulas of the oxidant and the reducing agent to reduce the oxidation number of the oxidant by the oxidation number of the reducing agent. The raised values ​​are equal.

Balance the number of atoms whose oxidation number has not changed, check whether the number of atoms on both sides of the chemical equation is equal, Change arrow to equal sign

It can more clearly point out the nature of redox reactions in aqueous solutions.

Concept: Using redox reactions to generate electric current, A device that converts chemical energy into electrical energy is called a primary battery

Electrons flow directionally from the negative electrode to the positive electrode, forming an electron flow (The direction of electron flow is exactly opposite to the direction of current)

A galvanic cell consists of two half cells (electrodes) and a salt bridge.

In the primary battery, the first stage (negative electrode) where electrons flow out is oxidized. Reduction reaction, the first stage where electrons flow into and the reduction reaction occurs is the positive electrode.

Metal-metal ion electrode

Non-metal-Non-metal ion electrode

Oxidation-reduction electrode

Metal-metal refractory salt electrode

The negative electrode is on the left and the positive electrode is on the right, represented by (-) and ( ) respectively. The corresponding compositions and phases are arranged in actual order from left to right.

A single vertical line is used to represent the phase interface, and a double vertical line "‖" is used to represent the salt bridge.

Indicate the concentration of the solution and the pressure of the gas.

If the solution contains two ions participating in the electrode reaction, they can be separated by commas. If there is no conductive substance in the electrode, an inert electrode must be added.

The electromotive force of the primary battery is equal to the potential difference between the positive and negative electrodes of the primary battery. The electromotive force of the primary battery can be measured using a potential difference meter.

The primary battery converts chemical energy into electrical energy by using the flow of electrons to generate current. And do the electrical work. Under constant temperature and constant voltage, the maximum electrical work done by the primary battery is equal to The product of the amount of electricity passing through and the electromotive force of the battery.

The primary battery can produce current, which means that there is a potential difference between the two poles of the primary battery, that is, each electrode Each has its own certain potential, which is called the electrode potential.

The electrode potential when all substances making up the electrode are in the standard state is called the standard electrode potential.