REDOX REACTIONS
SCH 4U1
Of the reactions studied last year, all involve the transfer of electrons
except double displacement reactions. The reactions involved in the transfer of
electrons are referred to as redox (oxidation-reduction) reactions.
Oxidation and reduction are two simultaneous processes. If an electron
travels from atom A to atom B, this will change the oxidation number of A
from ____ to ____ and of B from ____ to ____.
This can be shown as:
2 Mg(s) + O2(g) ---> 2MgO(s)
If the oxidation numbers of the reactants in their elemental form are zero,
observe the changes in the oxidation number in the products.
Reactants
Products
increase/decrease
Mg
__________
__________
oxidation number ______
O
__________
__________
oxidation number ______
Magnesium is described as being oxidized.
Oxygen is described as being reduced.
Since these processes occur at the same time, magnesium which is oxidized from 0
to 2+ is also the reducing agent. It reduces the oxygen.
Similarly, oxygen which is reduced from 0 to 2- is the oxidizing agent. It oxidizes
the magnesium.
MNEMONIC:
OIL RIG
Oxidation is loss - reduction is gain (of electrons)
LEO says GER
Loss of electrons oxidation – gain of electrons reduction