Class 11 Chemistry Chapter 8 Redox Reactions
Occurance of reduction and oxidation process simultaneously with the chemical reaction is called redox reaction.
Various phenomena like rusting of iron, browning of fruits, process of respiration, photosynthesis are result of redox reaction . However, redox reactions are mainly used in pharmaceuticals, industrial, metallurgical and in agricultural areas. Moreover, Redox, the name itself suggest reduction and oxidation. In this article we will talk about redox reaction in form of oxidation and reduction.
Oxidation
Oxidation is defined as,
” Addition of oxygen to an element or compound.”
It was also observed that oxidation is also possible by removal of hydrogen or electropositive element or by addition of electronegative element to substance. Therefore, oxidation is redefined as,
“Addition of oxygen or electronegative element to a substance or removal of hydrogen or electropositive elements from substance.”
For example –
Oxidation by addition of oxygen-
S(s) + O2(g) → SO2
By addition of electronegative element-
Mg(s)+ Cl2(g) → MgCl2(s)
Oxidation by removal of hydrogen-
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
Oxidation by removal of electropositive element-
2K4[Fe(CN)6](aq) + H2O2(g) → 2K3[Fe(CN)6](aq) + 2KOH(aq)
Reduction
It is defined as,
”Removal of oxygen or electronegative element from a substance or addition of hydrogen on electropositive element to a substance.”
Reduction reaction is opposite to oxidation.
For example:
Removal of oxygen from mercuric oxide-
2 HgO (s) heat→ 2Hg(l) + O2(g)
Removal of electronegative element chlorine from ferric chloride-
2FeCl3(aq) + H2(g) → 2FeCl2(aq) + 2HCl(aq)
Addition of hydrogen to ethylene-
CH2=CH2(g) + H2(g) → CH3-CH3(g)
Addition of mercury to mercuric chloride-
2HgCl2(aq) + SnCl2(aq) → Hg2Cl2(s) + SnCl4(aq)
In a chemical reaction oxidation and reduction occurs simultaneously,
“Where there is oxidation there is always reduction.”
Redox Reaction
Electron transfer in terms of Redox Reaction
Consider the reaction
2Na(s) + Cl2(g) → 2NaCl(s)
Ionic form of the reaction is
2Na(s) + Cl2(g) → 2Na+Cl–(s)
This reaction show transfer of electrons from sodium to chlorine. This can be seen easily in the reaction
2Na(s) → 2Na+(g) + 2e–
Cl2(g) + 2e-1 → 2Cl–(g)
These reaction are called as half reaction. With respect to half reaction, the reaction which shows loss or removal of electron, hence, such reactions are oxidation reaction. The reaction which shows gain or addition of electron is reduction reaction. In case of half reaction, sodium is oxidised, therefore, sodium becomes reducing agent. It is called reducing agent because it helps other component here it is chlorine to reduce. As chlorine is reduced it is called oxidising agent. It is because chlorine accepts electron from other component, thus, here it is sodium.
In short,
“Oxidation is due to loss of electron, oxidising agent are electron acceptor.”
“Reduction is due to gain of electrons, reducing agent are electron donor.”
Watch video on Redox Reaction here
Keywords: Reduction, Oxidation, Reducing agent, Oxidising agent, Electronegative element, Electropositive element.
Related articles
Covalent Bond
The Mole Concept
Acids and Bases
Working of Nuclear Reactor
Hybridization of Molecular Orbitals
This is truly useful, thanks.