Oxidation-reduction reactions or oxidation-reduction^[1] They are chemical reactions in which a change occurs in the oxidation number of the atoms of the reactants as a result of the transfer of electrons between them.

• oxidation It is a process of losing electrons by atoms, molecules or ions that results in an increase in positive charge or a decrease in negative charge.
• shorthand It is the process of gaining electrons by atoms, molecules or ions that results in a decrease in the positive charge or an increase in the negative charge.

More precisely, the oxidation process for an element (or for a molecule containing an element on which this process takes place) can be described as an increase in the oxidation number of this element, while reduction (or reduction) is the decrease in the oxidation number.

Example[عدل]

An example of such reactions is the reaction between iron and copper(II) sulfate:

$\displaystyle \mathrm Fe +\mathrm CuSO _4\longrightarrow \mathrm FeSO _4+\mathrm Cu$

Where the ionic reaction is:

$\displaystyle \mathrm Fe +\mathrm Cu ^2+\longrightarrow \mathrm Fe ^2++\mathrm Cu$

As iron is oxidized (the oxidation number of iron increased from 0 to +2):

$\displaystyle \mathrm Fe \longrightarrow \mathrm Fe ^2++2e^-$

And copper is reducing (the oxidation number of copper decreased from +2 to 0):

$\displaystyle \mathrm Cu ^2++2e^-\longrightarrow \mathrm Cu$

car battery[عدل]

A car battery is a close example of a redox reaction. The lead battery consists in its simplest form of a lead plate and a lead oxide plate. The two plates are in a sulfuric acid solution. The battery works by reducing the lead oxide plate and at the same time the lead plate is oxidized. The battery continues to function in this way until it is “discharged” when all the lead has been oxidized and all the lead oxide has been reduced. Then the battery needs to be recharged. And we do this by connecting the two poles of the battery to an external electrical source, that is, supplying it with energy from the outside. This electrical energy reverses the reaction that took place when the battery was discharged, so the lead plate was oxidized to lead oxide as it was originally, and the lead oxide plate was reduced to become pure lead as it was when the battery was purchased. After charging the battery, the battery can function again and provide us with electric current.

metal oxidation[عدل]

When a metal atom (metal) interacts with an oxygen atom, this reaction can be described by the following reaction equations:

$\displaystyle \mathrm M\longrightarrow M^2++2e^-$

Oxidation: M metal donates two electrons.

$\displaystyle \mathrm O_2+4e^-\longrightarrow 2\ O^2-$

Reduction: Each oxygen atom gains two electrons.

• The sum of these two reactions is called an “oxidation-reduction reaction” and is written as follows:

$\displaystyle \mathrm 2\ M+O_2\longrightarrow 2\ M^2++2\ O^2-$

Oxidation-reduction reaction: Oxygen oxidizes the metal, and it itself is reduced.

We find that oxygen tends to gain 2 electrons to reach a complete valence electron shell containing 8 electrons (octet rule). As for the metal, it can be given by giving two electrons to get rid of an incomplete shell and thus reach the next most stable electronic structure.

In our daily lives, we know iron oxidation and iron rust. To protect iron from rust, we rely on oxidation-reduction reactions.

Interactions used in industries[عدل]

Burning of fossil fuels such as coal, oil and natural gas is used in power stations to produce electrical energy. Many reactions are also used in mining, which are classic examples that show the importance of oxidation-reduction reactions in the industrial field.

blast furnace reaction[عدل]

In the blast furnace process, iron is reduced by coal. During this reaction, a side reaction results in carbon monoxide, which is a good reducing agent. Carbon monoxide does not react quickly and turns into carbon dioxide when the presence of oxygen is low in the furnace. .^[2]

$\displaystyle \mathrm 1)\ C+O_2\longrightarrow CO_2$

The furnace is heated by burning coal.

$\displaystyle \mathrm 2)\ CO_2+C\rightleftharpoons 2\ CO$

It produces carbon monoxide, which is a good reducing agent. Boudoir balance

$\displaystyle \mathrm 3)\ Fe_2O_3+3\ CO\longrightarrow 3\ CO_2+2\ Fe$

In the third step: iron oxide is reduced by carbon monoxide and pure iron is produced.

thermite reaction[عدل]

To prepare a number of metals from their oxides, aluminum can be used as a reducing material, when the metal is more inert (more noble) than aluminum. In this process, aluminum is used in the form of a powder, and the method is called the “thermal aluminum method”.

Iron oxide is mixed with aluminum powder – this agent is called thermite reaction – and it is ignited, so the iron oxide is reduced and molten iron is produced, which pours from the crucible of the mixture. This method is used to weld railroad tracks, and is also used in incendiary bombs.

$\displaystyle \mathrm 2\ Al+\ Fe_2O_3\longrightarrow Al_2O_3+2\ Fe$

in foodstuffs[عدل]

To prepare margarine, a catalytic hydrogenation process is used on vegetable oils.

$\displaystyle \mathrm R-CH=CH-R+H_2\longrightarrow R-CH_2-CH_2-R$

Hydrogenation of an unsaturated fatty acid by the addition of hydrogen.

Some salts such as sodium nitrate and potassium nitrate are also used to preserve the meat by covering it with these salts in a process called curing. Nitrite prevents the multiplication of microbes, as it reacts with myoglobin of meat and gives it a bright red color, Nitrosylmyoglobin. These reactions are also oxidation-reduction reactions:^[3]

$\displaystyle \mathrm Mb+NO_2^-\longrightarrow MMb^++NO$

Addition of nitrites to myoglobin produces metmyoglobin and nitrosyl.

Antioxidants are added to fatty foods to prevent their oxidation and spoilage, and antioxidants are oxidized instead.

Cell respiration and photosynthesis[عدل]

In the process of cell respiration and metabolism, glucose is converted to carbon dioxide by oxidation, and oxygen is reduced to water. The overall equation for this reaction can be written as follows:

$\displaystyle \mathrm C_6H_12O_6+6\ O_2\longrightarrow 6\ CO_2+6\ H_2O$

One glucose molecule reacts with 6 oxygen molecules and produces 6 carbon dioxide molecules and 6 water molecules.

The opposite occurs during the process of photosynthesis, where in the green matter of the plant, carbon dioxide interacts with water in the presence of light that provides them with energy – and they are converted into glucose and oxygen is released. The chemical reaction equation is as follows:

$\displaystyle \mathrm 6\;CO_2+12\;H_2O\longrightarrow \;C_6H_12O_6+6\;O_2+6\;H_2O$

This is the basic reaction in the plant that produces glucose, and from it, through other reactions, sucrose, starch, and others are produced.

Alcohol fermentation[عدل]

Yeast cells ferment a sugar solution and produce alcohol and carbon dioxide:

$\displaystyle \mathrm C_6H_12O_6\,+\,2\;ADP\,+\,2\;P_i\;\longrightarrow \;2\;C_2H_5OH\,+\,2\;CO_2\,+\,2\;ATP$

This method is used in industry on a large scale for the purpose of producing energy.

Preparation of methane[عدل]

There is a type of bacteria called Archabacteria that can prepare methane from carbon dioxide gas by extracting oxygen:

$\displaystyle \mathrm CO_2+4\ H_2\longrightarrow CH_4+2\ H_2O$

Electrochemistry[عدل]

Electrochemistry, as a branch of physical chemistry, is concerned with the study of chemical and electrical interactions. When an oxidation-reduction reaction generates an electric current, such a reaction is called an electrochemical reaction.

Electrochemical processes in electrochemistry take place on interfaces between two phases of matter. Accordingly, electrochemistry is the science that studies the processes that take place between a conductor of electrons (cathode as a solid state) and a conductor of ions (electrolyte).

The Nernst equation plays a key role here, and it describes the dependence of the electrode potential on the electrolyte concentration. The electrolyte can be analyzed by analyzing a redox reaction to obtain the concentration of the ions in the solution. In theory, Marcus theorem describes the entry of electrons from outside into a solution.

Galvanic cell, accumulator and electrolyte[عدل]

When a redox reaction is driven from the outside by applying an electric potential to it, then we call the process electrolysis. But when an electric potential arises as a result of an oxidation-reduction reaction, we call that a galvanic cell. The potentials of a redox reaction are described by the list of standard potentials[.Fromthatlistweknowthe“intensity”ofanoxidizingsubstanceorareducingsubstance.

Electrochemical redox reactions take place in a galvanic cell:

• During the electrolysis process and the accumulator charging process, we supply the system with electrical energy from the outside.
• When a battery is powered or an electric current is gained from a fuel cell, we get electrical energy. When the reaction takes place as a reversible process so that the electric current is equal to zero (I = 0), we get the Gibbs free energy for the reaction.

See also[عدل]

• reduction effort
• decomposition effort
• Electrochemistry
• Electrolysis
• shorthand
• oxidation
• oxidizer
• reversible reaction
• lead battery
• chemical dissociation
• List of standard efforts
• equivalent factor
• co-proportion reaction
• The donor-receiver principle

the reviewer[عدل]

• Physics portal
• Physical chemistry portal
• Analytical Chemistry Portal
• Chemistry portal

In Commons, photos and files on: Oxidation and reduction

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