Oxidation is one of the chemical reactions that you need to understand and know about in chemistry. Where, this oxidation certainly can not be separated by reduction. Both form a reduction-oxidation reaction or commonly called redox. The redox reaction itself is a reaction of releasing and binding of oxygen.
Redox is the term used to describe changes in the oxidation number or oxidation state of atoms in a chemical reaction. This can include simple redox processes, for example the oxidation of carbon to produce carbon dioxide or the reduction of carbon by hydrogen to produce methane (CH4).
Redox reactions themselves can also include complex processes, for example the oxidation of sugar in the human body through a series of complicated electron transfers. Where, oxidation and reduction precisely refer to changes in oxidation number because the actual transfer of electrons will not always occur. So oxidation is better defined as an increase in oxidation number and reduction as a decrease in oxidation number.
So, so that you understand and understand more clearly about oxidation and redox you need to pay attention to the full explanation. The following is an explanation regarding oxidation and redox, starting from the definition of oxidation to examples of redox.
Definition of Oxidation
Oxidation is a term that you need to understand, especially in studying chemistry based on the Big Indonesian Dictionary (KBBI), which states that oxidation is the combination of a substance with oxygen. Where oxidation itself is the release of electrons by a molecule, atom, or ion, this is different from reduction, which is the addition of electrons by a molecule, atom, or ion.
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The oxidation state includes an integer consisting of a positive, negative or zero value. Where for pure compound elements themselves the oxidation state is zero.
These oxidations and reductions of course refer to changes in oxidation number because the actual transfer of electrons will not always occur. So oxidation is better defined as an increase in oxidation number and reduction as a decrease in oxidation number. Such reactions involve the transfer of electrons.
So if it is based on the transfer or transfer of electrons, the reduction reaction is a point electron capture reaction. Meanwhile, the oxidation reaction is a reaction of releasing electrons. In practice, the transfer of electrons will always change oxidation number, but there are many reactions that need to be classified as redox even though there is no transfer of electrons in the reaction, such as something involving covalent bonds. Non-redox reactions that do not involve a change in formal charge are known as metathesis reactions.
Get to know the concept of Redox
So, in order to know more clearly about redox, in the following a discussion on the concept of redox has been presented. Where, chemical reactions involving redox or oxidation-reduction reactions are often used in titrimetric analysis rather than acid-base reactions, complex formation or precipitation. The ions of various elements exist in different oxidation states, which is why there are so many possible redox or oxidation-reduction reactions.
The development of the redox reaction concept resulted in 3 (three) concepts, namely classical theory, modern theory, and the concept of numbers. Then, what are the differences between the two? Let’s pay attention to the full discussion below.
The classical theory says that oxidation is a process of capturing oxygen and losing hydrogen. However, on the other hand reduction is a process of losing oxygen and capturing hydrogen.
The concept of redox has developed through various experiments, giving rise to the modern theory. Where, this modern theory says that oxidation is a process that results in the loss of one or more electrons from a substance. Substances that undergo oxidation will turn out to be more positive.
Meanwhile, reduction itself is a process that results in the acquisition of one or more electrons by a substance. Where, substances that undergo this reduction process will become more negative. From these two theories and reduction which is not only seen from the capture of oxygen and hydrogen but as a process of transferring electrons from one substance to another.
The concept of Oxidation Numbers
The concept of a redox reaction involving the transfer of electrons can only occur in ionic compounds. Meanwhile, in covalent compounds it is not. For this reason, a third redox concept emerged, which is based on changes in oxidation numbers or also called oxidation states.
Oxidation number is the positive and negative charges on an atom. The positive oxidation number element itself is generally an atom of a metal element, for example Na, Fe, Mg, Ca, and other metal elements. Meanwhile, elements with negative oxidation numbers are generally atoms of non-metallic elements, for example O, Cl, F, and other non-metallic elements.
According to the concept of change in oxidation number, states that a reduction reaction is a reaction in which the oxidation number decreases. Meanwhile, the oxidation reaction itself is a reaction that experiences an increase in oxidation number.
Where, there are 8 (eight) rules in determining the oxidation number of an atom that you must know, including the following:
1. The concept of the oxidation number of free elements in the form of atoms and molecules, namely O
Atomic free samples.
C, Ca, Cu, Na, Fe, Al, Ne = 0
Free examples are molecules.
For example H2, O2, CI2, P4, S8, = 0.
2. The concept of the oxidation number of monoatomic and polyatomic ions according to the type of ionic charge
The oxidation numbers of monoatomic ions Na+, Mg2+, and AI3+ are +1, +2, and +3, respectively.
The oxidation numbers of polyatomic ions NH4+, SO42-, and PO43- are +1, -2, and -3, respectively.
3. The concept of the oxidation number of elements in metal groups IA, IIA, and IIIA according to group
An example of the oxidation number of Na in a NaCl compound is +1
Such as: IA = H, Li, Na, K, Rb, Cs, Fr = +1.
An example of the oxidation number of Mg in the compound MgSO2 is +2.
Such as: IIA = Be, Mg, Ca, Sr, Ba, Ra = +2.
An example of the oxidation number of Al in the AI203 compound is +3.
Like IIIA = B, Al, Ga, In, Tl = +3.
4. The concept of oxidation numbers for more than one transition group or group B elements
Oxidation numbers of Cu = +1 and +2.
Au oxidation number = +1 and +3.
Sn oxidation numbers = +3 and +4.
5. The concept of the total oxidation number of the elements that form ions = the total charge
For example: NH4+ = +1
6. The concept of the sum of the oxidation numbers of the elements that form compounds = 0
For example: H2O = 0
7. The concept of Hydrogen Oxidation Number (H) When Associated with Metals = -1 But when H is related to non-metals = +1
For example: The oxidation number of H in AIH3 = -1
8. Concept of Oxygen Number (O) in Peroxide Compounds = -1 and Oxidation Number of O in Non Peroxide Compounds = -2
For example: The oxidation number of O in the compound BaO2 = -1.
How to Determine Reduction and Oxidation (Redox) Reactions Based on the Concept of Increasing and Decreasing Oxidation Numbers
In reduction and oxidation (redox) reactions, there are several elements that act as reducing agents and oxidizing agents. Where, the substance that is being oxidized is called a reducing agent, while the substance that is being reduced is called an oxidizing agent.
Try to look at the following example:
Reaction Mg(s) + 2HCl —–> MgCl2(aq) + H2(g)
Because Mg is a free element, so the oxidation number of Mg = 0. Then, the oxidation number of H in the 2HCl compound is +1 because H elements are related to other elements and H is a group of IA. Furthermore, because H = +1, it means that Cl = -1 so that the total oxidation number of 2HCl = 0.
On the right-hand side, the oxidation number of Mg in the compound MgCl is +2 because Mg is bonded and is a group IIA element. This is because Cl has an index of 2, so the oxidation number of Cl = -1 so that the total oxidation number of MgCl2 = 0. In addition, because H2 is a free element, the oxidation number has a value of 0. Where, the element Mg experiences an increase in oxidation number from 0 to +2 So it will undergo an oxidation reaction.
So that the element Mg can be said to be a reducing agent. Meanwhile, element H will experience a decrease in its oxidation number from +1 to 0, so it will undergo a reduction reaction. Therefore, HCl is called an oxidizing agent.
Definition of Oxidizing and Reducing
An oxidizing agent is a compound that has the ability to oxidize other compounds or is commonly known as a compound that accepts electrons. Where, the oxidizer itself is a compound that has elements with high oxidation numbers, for example H2O2, MnO4-, CrO3, Cr2O72-, OsO4, and other very electronegative compounds.
Meanwhile, a reducing agent is a compound that has the ability to reduce other compounds or is commonly known as an electron donating compound. Compounds in the form of reducing agents are found in metal elements. For example Lu, Na, Mg, Fe, Zn, and Al. Another type of reducing agent is a hybrid transfer reagent, such as NaBH4 and LiALH4.
Examples of Redox Reactions
One example of a redox reaction is between hydrogen and fluorine:
H2 + F2 a 2 HF
You can write all these reactions as 2 (two) half reactions:
Oxidation reaction: H2 a 2H+ + 2e-
Reduction reaction: F2 + 2e- a 2F-
Analyzing each half reaction will make the whole chemical process appear more clearly. That is because there is no change in total charge during a redox reaction, the total excess electrons in an oxidation reaction must equal the number consumed in a reduction reaction.
Elements even in this molecular form often have an oxidation number of zero. In the above reaction hydrogen is oxidized from 0 to +1, while fluorine is reduced from 0 to -1. When oxidation and reduction reactions are combined the electrons involved reduce each other:
H2 a 2H+ + 2e-
F2 + 2e- à 2F-
H2 + F2 a 2H+ + 2F-
And the ions will combine to form hydrogen fluoride:
H2 + F2 a 2H+ + 2F- a 2 HF
This is the discussion about oxidation. Hopefully the information about oxidation above can be helpful and useful for readers.