These are reactions where electrons are transferred from one
species (atom, molecule or ion) to another. We can write 'half' equations to
show only what happens to the species losing electrons or a different 'half'
equation to show the species gaining electrons.
Chemistry x - OXIDATION AND REDUCTION : Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electron(s) is called as oxidation.
2Mg + O2 →2MgO (addition of oxygen)
H2S + Br2 → 2HBr + S (removal of hydrogen)
The whole equation is put together by making sure that the
numbers of electrons are balanced in each half equation and adding them
together (when the electrons will cancel out)
Oxidation is a chemical process
in which there is a loss of electrons. The species, which gets oxidized becomes
more positive or less negative, e.g.,
Na → Na+ + e- (Na is oxidized to Na+ )
Fe2+→ Fe3+ + e- (Fe2+ is oxidized to Fe3+)
Fe2+
Reduction is a chemical process
in which there is a gain of electrons. The species, which gets reduced becomes
more negative or less positive, e.g.,
Cl2 + 2e- → 2Cl- (Cl2 is reduced to Cl-)
S + 2e-→ S2- (S is reduced to S2- )
S + 2e-
The Oxidizing agent is the species which accepts
electrons, e.g.,
Sn4+ + 2e- → Sn2+ (Sn4+ is an oxidizing agent)
F2 + 2e-→ 2F- (F2 is an oxidizing agent)
F2 + 2e-
The Reducing agent is the substance which loses
electrons, e.g.,
Hg+ → Hg2+ + e-
(Hg+ is a reducing agent)
Fe2+→ Fe3+ + e- (Fe2+ is a reducing agent)
Fe2+
Examples
2FeCl2 + Cl2 →
2FeCl3
The iron changes from 2+ to 3+ and is therefore oxidised
(removal of electrons)
The chlorine gains an electron to go from 0 to -1 and is
therefore reduced (addition of electrons)
Zn + CuSO4 →
Cu + ZnSO4
The zinc changes from oxidation state 0 to +2 (removal of
electrons) it is oxidised (animation)
The copper changes from 2+ to 0 and is oxidised and is
therefore reduced (addition of electrons)
Cr2O72- + 3SO2 + 2H+ →
2Cr3+ + 3SO42- + H2O
The chromium changes from +6 to +3 and is therefore reduced
(gain of electrons)
The sulphur changes from +4 to +6 and therefore loses
electrons = oxidation (loss of electrons)
2KI + Br2 → 2KBr
+ I2
The iodide ions (oxidation number = -1) change to iodine
(oxidation number = 0) : oxidation
Bromine (element, oxidation number = 0) changes to bromide
ions (oxidation number = -1) : reduction
5Fe2+ + MnO4- + 8H+ → 5Fe3+
+ Mn2+ + 4H2O
The iron changes from 2+ to 3+ and is oxidised (removal of
electrons)
The manganese atom changes from +7 to +2 and is therefore
reduced (addition of electrons)
More post describing redox reaction
The Effects of Oxidation Reactions : Many metals are chemically
active elements and get easily affected by substances like moisture,
air, acids, etc. Example-Iron articles that are shiny when new, but get
coated with a reddish brown powder when left for some time. This process
is commonly known as rusting of iron. Rusting eventually causes
structural weakness and disintegration of the metal.
When a metal is
attacked by substances around it, it is said to corrode and this process
is called corrosion. Corrosion causes deterioration of essential
properties in a material..............Read more
In our daily life we come across phenomena like fading of the colours of the clothes, burning of combustible substances like cooking gas, wood and coal, .................................... Read more
science class 10 oxidation, reduction and redox chemical reaction
Chemistry x - OXIDATION AND REDUCTION : Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electron(s) is called as oxidation.
2Mg + O2 →2MgO (addition of oxygen)
H2S + Br2 → 2HBr + S (removal of hydrogen)