1. Redox
Reaction

3. Oxidation is a reaction
where oxygen
combines with an
element/compound to
form another
substance

4. Oxidation – Gain of oxygen
When calcium burns in oxygen, the following
reaction takes place
calcium + oxygen  calcium oxide
2Ca(s) + O2  2CaO(s)
Since calcium has gained oxygen. It has be
oxidised. Hence this is oxidation.

5. Oxidation – Loss of Hydrogen
When ammonia is passed over heated copper(II)
oxide, the following reaction takes place.
ammonia + copper(II) oxide  nitrogen +
copper + water vapour
2NH3(g) + 3CuO(s)  N2(g) + 3Cu(s) + 3H2O(g)
Since ammonia has lost hydrogen, it has been
oxidised.

6. Oxidation – Loss of Electrons
Oxidation can still take place despite having no
oxygen/hydrogen. When a substance loses
electrons it is considered oxidation.
magnesium + chlorine  magnesium chloride
Mg(s) + Cl2(g)  MgCl2(s)

7. What is Reduction?

8. Definition Of Reduction
• Reduction is a chemical reaction where it loses
oxygen, gain hydrogen, gain electron and have a
decrease in oxidation state by a molecule, atom
or ion.
• A reactant that reduces another substance is a
reducing agent.
• The reducing agent transfers electrons to
another substance, it reduces others, and is thus
itself oxidized. And, because it "donates"
electrons, it is also called an electron donor.

9. Reduction-Loss Of Oxygen
When zinc burns in copper(II) oxide, the
following reaction takes place.
Zinc + copper oxide  Zinc oxide + copper
Zn(s)+CuO(s)  ZnO(s)+Cu(s)
Since Zinc has gain oxygen,it is oxidised.
Copper(II) oxide loses oxygen,thus it is reduced.

10. Reduction-Gain Of Hydrogen
When nitrogen burns with hydrogen gas, the
following reaction takes place.
Nitrogen +Hydrogen  Ammonia
N2 + 3H2  2NH3
Nitrogen gain hydrogen, thus it is being reduced.

11. Reduction-Gain Of Electron
When iron reacts with chloride acid, the
following reaction takes place.
Iron + chlorine  Iron(III) + Chloride
2Fe2++Cl2  2Fe3++2Cl-
Since iron loses electron, it is oxidised. Chlorine
gains electron, thus it is reduced.

12. Common Reducing Agent
• Lithium aluminium hydride (LiAlH4)
• Nascent (atomic) hydrogen
• Sodium amalgam
• Diborane
• Sodium borohydride (NaBH4)
• Compounds containing the Sn2+ ion, such as tin(II) chloride
• Sulfite compounds
• Hydrazine (Wolff-Kishner reduction)
• Zinc-mercury amalgam (Zn(Hg)) (Clemmensen reduction)
• Diisobutylaluminum hydride (DIBAL-H)
• Lindlar catalyst
• Oxalic acid (C2H2O4)
• Formic acid (HCOOH)
• Ascorbic acid (C6H8O6)
• Phosphites, hypophosphites, and phosphorous acid
• Dithiothreitol (DTT) – used in biochemistry labs to avoid S-S bonds
• Compounds containing the Fe2+ ion, such as iron(II) sulfate
• Carbon monoxide(CO)
• Carbon (C)

13. Oxidation State

14. The oxidation state is the
charge an atom of an
element would have if it
existed as an ion in a
compound.

15. To work out the oxidation state of an atom,
we apply the following rules:
Rule Example Oxidation state
1. The oxidation state of a Cu, S, Cl2 0, 0, 0
free element is zero.
2. The oxidation state of a K+, Zn2+, Cl-, O2- +1, +2, -1, -2
simple ion is the same as
the charge on the ion.
3. The oxidation states of Ca, C, 3O +2, +4, 3x(-2)=-6
the atoms present in the
formula of a compound All add up to zero.
add up to zero. The
example shown here is
CaCO3 .
4. The total of the S, 4O +6, 4x(-2)=-6
oxidation states of the
atoms in a polyatomic ion All add up to -2.
is equal to the charge on
the ion. The example
shown here is SO4 2- .

16. Solution to question: Find the
oxidation state of each element in
ammonium sulfate.
(NH4)2SO4
Since hydrogen in NH4 has an o.s of +1,
Ammonium has a charge of 1.
Let n be x
2(x+4(1))=2
2x-2-8
x=-3
Hence nitrogen has an o.s of -3

17. Since oxygen in SO4 has an o.s of -2,
Sulfate has a charge of -2.
Let s be y
y+4(-2)=-2
y-8=-2
y=6
Hence sulfur has an o.s of 6.

18. Source
CHEMISTRY Matters textbook
Google

19. Done by
• Edwin
• Kian Leong
• Jeremy
• Melvan