Question

In the balanced equation x, y, z are:
$x{\text{ClO}}_4^ - + {\text{yMn}}{{\text{O}}_{\text{2}}} + {\text{zO}}{{\text{H}}^ - } \to {\text{xCl}}{{\text{O}}^ - } + {\text{yMnO}}_4^{2 - } + \dfrac{{\text{z}}}{{\text{2}}}{{\text{H}}_{\text{2}}}{\text{O}}$
A.2,3,6
B.1,3,4
C.1,3,6
D.2,6,6

Answer 1

Hint:A balanced chemical reaction is a reaction which has equal numbers of atoms of each element on both sides of an equation. In a redox reaction, it is important to balance the number of electrons transferred through the course of reaction. A balanced reaction follows both electrical neutrality and the law of conservation of mass.

Complete step by step answer:
The given reaction is a redox reaction in which permanganate ion is the oxidizing agent and oxalate ion is the reducing agent. First we balance the number of atoms of each element except hydrogen and oxygen. We get,
${\text{ClO}}_4^ - + {\text{Mn}}{{\text{O}}_{\text{2}}} + {\text{O}}{{\text{H}}^ - } \to {\text{Cl}}{{\text{O}}^ - } + {\text{MnO}}_4^{2 - } + {{\text{H}}_{\text{2}}}{\text{O}}$
$Mn{O_2} \to MnO_4^{2 - }$
Manganese in the above reaction undergoes a change in oxidation state from $ + 4 \to + 6$. It loses two electrons.
$ClO_4^ - \to Cl{O^ - }$
Chlorine in the above reaction undergoes a change in oxidation state from $ + 7 \to + 1$. It gains six electrons.
Cross multiplying the equations with the electrons transferred, we get,
${\text{ClO}}_4^ - + 3{\text{Mn}}{{\text{O}}_{\text{2}}} + {\text{O}}{{\text{H}}^ - } \to {\text{Cl}}{{\text{O}}^ - } + 3{\text{MnO}}_4^{2 - } + {{\text{H}}_{\text{2}}}{\text{O}}$
Now that the electrons are balanced, we balance the hydrogen and oxygen atoms keeping in mind to also neutralize the charge on both sides of the reaction. We get,
${\text{ClO}}_4^ - + 3{\text{Mn}}{{\text{O}}_{\text{2}}} + 6{\text{O}}{{\text{H}}^ - } \to {\text{Cl}}{{\text{O}}^ - } + 3{\text{MnO}}_4^{2 - } + 3{{\text{H}}_{\text{2}}}{\text{O}}$
Comparing to the equation in the question, $x{\text{ClO}}_4^ - + {\text{yMn}}{{\text{O}}_{\text{2}}} + {\text{zO}}{{\text{H}}^ - } \to {\text{xCl}}{{\text{O}}^ - } + {\text{yMnO}}_4^{2 - } + \dfrac{{\text{z}}}{{\text{2}}}{{\text{H}}_{\text{2}}}{\text{O}}$ we get, $x = 1,y = 3,z = 6$

Hence, the correct answer is C.

Note:
We know that the law of conservation of mass states that matter can neither be created nor destroyed and nor can one element be transfused into the other during a chemical reaction, thus the amount of each element must be the same before and after the reaction. Also, the electrical neutrality of a reaction must be maintained at all times, that is, the charges on both sides of the reaction must be balanced.