Question: \[{{S}}{{{O}}_{{2}}}\] reduces \[{{MnO}}_{{4}}^{{ - }}\] to \[{{M}}{{{n}}^{{{2 + }}}}\]. Number of e...

Question

${{S}}{{{O}}_{{2}}}$ reduces ${{MnO}}_{{4}}^{{ - }}$ to ${{M}}{{{n}}^{{{2 + }}}}$ . Number of electrons involved in the reduction of ${{MnO}}_{{4}}^{{ - }}$ to ${{M}}{{{n}}^{{{2 + }}}}$ is:

Answer 1

Solution

Oxidation is the loss of electrons and reduction is the process of gain of electrons and the oxidation number of an atom is a number that gives information of the total number of electrons lost or gained by it. Most of the elements undergo oxidation to get stability.

Complete step by step answer:
There are certain rules for finding the oxidation number, they are,
A.Oxidation number of a free element is zero.
B.Oxidation number for monatomic ions is the net charge corresponding to the ion.
C.Oxidation number of a hydrogen atom is $+ 1$ ., but when it is bonded to an element with less electronegativity, the oxidation number is $- 1\,$ .
D.Oxidation number of oxygen is $- 2$ in most of its compounds, but in peroxides, the oxidation is $- 1\,$ .
E.Oxidation number of alkali metals are $+ 1$ in their compounds.
F.Oxidation number of all alkaline earth metals (group 2 elements) are ${{ + 2}}$ in their compounds.
G.Oxidation number for a halogen (group 17 elements) is $- 1\,$ .
H.Oxidation number in the case of neutral compound is the sum of all the oxidation numbers of the constituent atoms
I.Oxidation number of a polyatomic ion is the sum of all the oxidation numbers of the atoms that constitute them equals the net charge of the polyatomic ion.
Here, let ${{x}}$ be the oxidation no. of ${{Mn}}$ in ${{MnO}}_4^ -$ , then
${{ - }}{{x + 4 \times ( - 2) = - 1}}$
${{x = + 7}}$
Thus the oxidation number of ${{Mn}}$ in ${{MnO}}_4^ -$ is ${{ + 7}}$ and the oxidation number of ${{Mn}}$ in ${{M}}{{{n}}^{{{2 + }}}}$ is ${{ + 2}}$ .
Here the oxidation number of manganese changes from +7 to +2, therefore, number of electrons involved in the reduction of ${{MnO}}_4^ -$ to ${{M}}{{{n}}^{{{2 + }}}}$ is ${{5}}$ .
Hence the answer is ${{5}}$

Note: Some common redox reactions are, Combustion reaction, is a type of redox reaction which occurs between oxygen and compound to form oxygen containing products, Disproportionation reaction, It is a type of redox reaction in which a single reactant is reduced and oxidized. It is also known as an auto-oxidation reaction.