Oxidation-Reduction & Redox Reactions
In earlier sessions, we learned that a chemical reaction takes place on the basis of loss or gain or sharing of electrons between different elements taking part in that reaction. Because of this loss, gain or sharing of electrons, element changed its state and charge on it, either the charge goes positive or negative based on loss or gain of electrons.
In this session we are going to discuss about the concepts based on loss or gain of electrons and the reactions based on that.
1. Oxidation-Reduction
4. Redox Reactions
Previous learning sessions:
Oxidation-Reduction
A reaction has two sides, reactants (elements or compound before reaction) and products (elements of compounds after reaction).
Oxidation
- When an elements ionic state (in comparison to before and after reaction) moves towards a positive direction.
- It means, element looses electron during reaction and gains more positive charge after reaction.
- For ex. if elements (A, B, C) has (-1, 0, +1) charge before reaction, then after reaction their charge can become (0, +1, +2). It means, elements charge have moved towards positive direction and become more positive.
- It’s never happens that, all elements in reaction will move towards positive direction. But, the elements that has gain more positive charge are called Oxidized or Oxidation elements.
Reduction
- When an elements ionic state (in comparison to before and after reaction) moves towards a negative direction.
- It means, element gains electron during reaction and gains more negative charge after reaction.
- For ex. if elements (A, B, C) has (-1, 0, +1) charge before reaction, then after reaction their charge can become (-2, -1, 0). It means, elements charge have moved towards negative direction and become more negative.
- It’s never happens that, all elements in reaction will move towards negative direction. But, the elements that has gain more negative charge are called Reduced or Reduction elements.
Oxidation-Reduction with Oxygen
- Oxygen is an electro-negative element. It means, it tries to gain electrons to get more stable by fulfilling its outer most orbital.
- If an element gets combine with Oxygen, then that element looses electrons and gains positive charge, means it gets oxidized.
- Oxidation of Iron = 4Fe + 3O2 → 2Fe2O3
- Oxidation of Carbon = C + O2 → CO2
- If an element removes from Oxygen, then that element gains electron and gains negative charge, means it gets reduced.
- Reduction of Copper = 2CuO → 2Cu + O2
- Reduction of Carbon = CO2 → C + O2
A + O → A2+O2-
Here, element A has charge 0 before reaction, but have charge +2 after reaction. Element A is oxidized.
A2+O2- → A + O
Here, element A has charge +2 before reaction, but have charge 0 after reaction. Element A is reduced.
Oxidation-Reduction with Hydrogen
- Hydrogen is an electro-positive element. It means, it tries to lose electrons to get more stable by fulfilling its outer most orbital.
- If an element gets removes from Hydrogen, then that element looses electrons and gains positive charge, means it gets oxidized.
- Oxidation of Sulphur = H2S → 2H + S
- Oxidation of Carbon = CH3OH → HCHO
- If an element combine with Hydrogen, then that element gains electron and gains negative charge, means it gets reduced.
- Reduction of Sulphur = H2 + S → H2S
- Reduction of Carbon = HCHO → CH3OH
A–H+ → A + H
Here, element A has charge -1 before reaction, but have charge 0 after reaction. Element A is oxidized.
A + H → A–H+
Here, element A has charge 0 before reaction, but have charge -1 after reaction. Element A is reduced.
Redox Reaction
Redox is short form for Reduction-Oxidation.
It means reduction and oxidation happens simultaneously in a reaction. If one element gets oxidized then another element gets reduced.
