Transcript Oxidation

Iron II oxide
Iron III oxide

Oxidation number of all elements in its
free state is ZERO.
Eg.Cu(s) or N2 (g)
 1. Determine the oxidation number of Cl2
(g)
Oxidation number=0
2.Determine the oxidation number of Zn(s)
Oxidation number=0


The oxidation number of elements that
exist as simple ions in ionic compounds is
the same as the charge on the ion.
Eg. NaCl: Na+ Cl- ions present
Oxidation numbers of:
Na = +1, Cl= -1
3. In the compound AlCl3 what are the
oxidation numbers of Al and Cl?

Al=+3
 Cl=-1


The sum of all the oxidation numbers in a
compound is ZERO.

Eg. Al2O3
(2 x oxidation number Al) + (3 x oxidation number O) = 0
(2 x +3) + (3 x -2)
+6
+
-6
=0
=0

The sum of all oxidation numbers of
elements in a radical is equal to the
charge on the ion.
Eg. To calculate oxidation # of S in SO4 2(Oxidation number of S) + 4(oxidation number of O) = -2
S + 4(-2) = -2
S – 8 = -2
S = -2 + 8
S = +6

4. Calculate the oxidation number of each of the
following:

(a) Mn in KMnO4
(b) Cr in Cr2O7 2(c) S in H2S
(d) V in VO 2+



5. Calculate the oxidation number for each element
in the equation:
Fe2O3(s) + 3C(s) → 2 Fe(s) + 3CO(g)

Some elements have fixed oxidation
states which can be determined from
their position in the periodic table since it
corresponds with its ion charge.
 Others have variable oxidation states
which need to be calculated.
 There are rules to consider when
calculating oxidation #. These are:

Oxidation number of all elements in its
free state is ZERO.
 The oxidation number of elements that
exist as simple ions in ionic compounds is
the same as the charge on the ion.

The sum of all the oxidation numbers in a
compound is ZERO.
 The sum of all oxidation numbers of
elements in a radical is equal to the
charge on the ion.


To assess what you have learnt today.
Let’s play MAHJONG CHEM!!!!
http://www2.stetson.edu/mahjongchem/
RULES:
1. Work out the oxidation # of the highlighted
element (red) in each formula shown on
your own paper and try to match it to a
lighted number square.
2. When both are clicked and they are
correct they will disappear giving way to
more squares.


The computer will tell you if there are any
moves left and will keep your score. If
there are no moves left I will record your
score and you may start a new game.

You have 15 mins. Let us see who wins by
scoring the most in that time!!!