Question

In the oxidation of ${C_2}O_4^{2 - }$ ion by $MnO_4^ - $ ion in acidic medium, moles of ${H^ + }$ ion needed per mole of ${C_2}O_4^{2 - }$ ion is-
(A) $16$
(B) $8$
(C) $3.2$
(D) $6.4$

Answer 1

Hint: The given reaction is an example of a redox reaction. In these types of chemical reactions, the oxidation state of atoms or molecules gets changed. Oxidation state can be defined as the total number of electrons gained or lost by an atom while forming a bond with another atom.

Complete step-by-step solution:A redox reaction is given as a chemical reaction which is governed via transfer of electrons between two atoms or molecules participating in the reaction. This transfer of electrons is observed by calculating the changes that occur in the oxidation states of the reacting species.
In Redox reactions both oxidation and reduction take place in the same reaction. In this type of chemical reaction, one species is oxidised and the other is reduced.
The molecule in which the addition of electrons takes place gets reduced, and the other from which the removal of electrons takes place gets oxidized.

To find the number of moles of ${H^ + }$ ion needed per mole we have to write the balanced redox reaction. First we will write the half reaction of reduction of permanganate ion to $M{n^{2 + }}$. It will be:
$MnO_4^ - + 5e + 8{H^ + } \to M{n^{2 + }} + 4{H_2}O.......(i)$
The oxalate ion will get oxidized and gain $2e$ the reaction for that will be:
${C_2}O_4^{2 - } \to C{O_2} + 2e............(ii)$
To balance the reaction, we have to multiply (i) by $2$. The net final reaction will be:
$2MnO_4^ - + 5{C_2}O_4^{2 - } + 16{H^ + } \to 2M{n^{2 + }} + 8{H_2}O + 10C{O_2}$
Hence, we can say that $16$ moles of ${H^ + }$ ion are needed per mole of ${C_2}O_4^{2 - }$ ion in an acidic medium.

Therefore, Option (A) is correct.

Note: Oxidation numbers represent the potential charge present on an atom in its ionic form. If the atom's oxidation is decreased in a reaction, then it is said to get reduced. If it increases, then the atom is said to get oxidized.