Redox- Is when oxidation and reduction are taking place at the same time(simultaneously) .
Oxidation- Is the loss of electrons or oxidation is said to occur when there is an increase in oxidation state.
Reduction- Is the gain of electrons or when there is a decrease in oxidation state .
Cu2+ + Zn --> Cu + Zn2+
For the example given above,Zn has been oxidised (lost electrons ) and Cu has been reduced (gain electrons ).
Remember when a specie losses electron(s) it becomes positively charged and when a specie gains electron(s) it becomes negatively charged .
OXIDATION STATES
Rules
- All elements in their standard state have zero(0) oxidation state .example Na ,Cl2
- Na+ has oxidation state of +1 and Mg2+ has oxidation state of +2
- Cl- has oxidation state of -1
- Hydrogen has oxidation state of +1 except in the hydrides where it is -1
How to find the oxidation states of elements in a compound
Eg 1.find the ox of c in Co2
C -4 =0 note : O has ox of -2 and there are two molecules of it so the total oxidation state is
2 * -2 = -4
C = +4
2. what is the oxidation state of
N in No3 - ? 3.Mn in MnO4 -
N- (3*2)= -1 Mn -(2*4) = -1
N-6 = -1 Mn -8 = -1
N= -1+6 Mn = -1 +8
N= +5 Mn =+7
4.S in SO42−
S -(2*4) = -2
S-8= -2
S= -2 +8
S= +6
Role of oxidation state in naming species
Manganese(iv) oxide -Mn has +4 oxidation state in MnO2 hence the name
Sulphur (vi) oxide - S has + 6 oxidation state
dichromate (vi) - Cr has oxidation state of +6
