|
MLearner mobile |
your portal to mobile learning |
Redox Reactions
1. Redox reactions involve a TRANSFER of ELECTRONS from substance A to substance B.
When electrons are transferred, charge numbers of ions change.
----------------------------------
As an example, assume an Fe2+ ion changes to the Fe3+ ion.
When numbers have changed, such a reaction is called a REDOX reaction.
(There are many reactions where these numbers do not change.)
----------------------------------
2. Assume A loses electrons :
A is said to have undergone an oxidation ½ reaction (O½R)
(the charge numbers increase)
A itself is called a reducing agent (RA) (since A would have caused such a reaction in B)
----------------------------------
3. Substance B would gain these electrons
B is said to have undergone a reduction ½ reaction (R½R)
(the charge numbers decrease)
B itself is called an oxidising agent (since B would have caused such a reaction in A)
----------------------------------
Easy ways to remember
The triple statement. The “three words” go together.
----------------------------------
O½R
loss of e-
RA
We say the Fe2+ ion has undergone an oxidation ½ reaction, by losing electrons. The Fe2+ ion is called a reducing agent.
----------------------------------
R½R
gain of e-
OA
We say the Mn+7 ion has undergone a reduction ½ reaction, by gaining electrons. The Mn+7 ion is called an oxidising agent.
----------------------------------
N.B. All you have to do is to check whether the charge numbers increase or decrease for a particular substance on either side of the arrow.
If the charge increases, then it is an O½R
If the charge decreases, then it is a R½R