Redox chemical reaction
A chemical reaction in which oxidation and reduction
reactions occur simultaneously is called redox reaction.
Oxidation
Oxidation is a chemical reaction in which a substance combine with oxygen or electronegative element or remove hydrogen atom or remove electropositive element or loses electrons.
Addition of oxygen:
C + O2 → CO2 (oxidation of carbon)
Addition of electronegative element:
Fe + S → FeS (oxidation of Iron)
Removal of hydrogen:
H2S + Br2 → 2 HBr + S (oxidation of sulphide)
Removal of electropositive elements:
2KI + H2O2 → I2 + 2 KOH (oxidation of iodide)
Loss of electron/electrons :
Zn→Zn2+ +2e
(Zn) loses two electrons to form zinc ions (Zn2+).
This loss of electrons is oxidation.
Reduction
Reduction is a chemical reaction in which a substance combine with hydrogen or electropositive element or remove oxygen atom or remove electronegative element or gain electrons.
Addition of hydrogen:
N2 + 3H2 → 2NH3 ( reduction of nitrogen)
Addition of electropositive element:
SnCl2 + 2HgCl2 → SnCl4 + Hg2Cl2 ( reduction of mercuric chloride)
Removal of oxygen
ZnO + C → Zn + CO (reduction of zinc oxide)
Removal of electronegative element
2FeCl3 + H2 → 2FeCl2 + 2HCl (reduction of ferric chloride)
Loss of electron/electrons :
Cu2+ +2e → Cu
( Cu2+) gains two electrons to form copper (Cu).
This gain of electrons is reduction.
Oxidizing agent
A chemical substance that oxidizes other substances during chemical reaction is called oxidizing agent. It is also called oxidant.
Common oxidant agents are:
- Oxygen (O2)
- Ozone (O3)
- Hydrogen peroxide (H2O2) and other inorganic peroxides, Fenton's reagent.
- Fluorine (F2), chlorine (Cl2), and other halogens.
- Nitric acid (HNO3) and nitrate compounds such as potassium nitrate (KNO3), the oxidizer in black powder.
- Potassium chlorate (KClO3)
An oxidizing agent, or oxidant, gains electrons and is reduced during chemical reaction.
Reducing agent
A chemical substance that reduces other substances during chemical reaction is called reducing agent. It is also called reductant
Common oxidant agents are: Hydrogen, the alkali metals, formic acid, oxalic acid, and sulfite
compounds.
An reducing agent, or reductant, lose electron(s) and is oxidized during chemical reaction.
Oxidation number
Oxidation number of atom of element refers the total number
of electrons that an atom either gains or losses in order to form a chemical
bond with another atom(s).
It is also termed as the oxidation state of atom .
Determining Oxidation Numbers
Some rules that
help to determine the oxidation number of an atom or molecule:
- Oxidation
number of an element in its natural state is always zero.
Example:-
Oxidation number of Ca =>0
Oxidation number of Cl2 => 0
Oxidation number of Na =>0
- Oxidation
number of group I element is +1 in a compound except H.
Example:-
Oxidation number of Na in NaCl => +1
Oxidation number of H in H2O => +2 , because there are two atoms of H
- Oxidation number group 2 elements have +2 .
Example:-
Oxidation number of Be => +2
Oxidation number of H in B => +3 - Hydrogen
has +1 and -1 as oxidation number. When hydrogen is combined with non-metal oxidation
number is taken as +1 and in case of metal it is taken as -1.
Example:-
Oxidation number of H in HCl=> +1
Oxidation number of H in NaH => -1
- All
noble gases have their oxidation number as 0.
Example:-
Oxidation number of Ar(Argon)=> 0
Oxidation number of Ne(Neon)=> 0 - Halogen elements have -1 as their oxidation number.Example:-
Oxidation number of Cl => -1
Oxidation number of F => -1 - Oxygen has an oxidation of -2 in most of its compounds. However, in the case of peroxides, the oxidation number corresponding to oxygen is -1.
- The sum of all oxidation numbers in a compound must be zero.
