Question

For decolourization of 1 mole of $ KMn{{O}_{4}} $ , the moles of $ {{H}_{2}}{{O}_{2}} $ required is?
(A) 1/2
(B) 3/2
(C) 5/2
(D) 7/2

Answer 1

Hint: We need to find the number of moles of $ {{H}_{2}}{{O}_{2}} $ . Here oxidation and reduction both are taking place. Hence, we need to balance the redox reaction. From the reaction, we can use stoichiometric coefficients to find the number of moles of reactants and products.

Complete step by step answer
We already know that 1 mole of $ KMn{{O}_{4}} $ reacts with $ {{H}_{2}}{{O}_{2}} $ .
Acidified $ KMn{{O}_{4}} $ is decolourised by $ {{H}_{2}}{{O}_{2}} $ in the following way:
 $ 2KMn{{O}_{4}}+3{{H}_{2}}S{{O}_{4}}\to {{K}_{2}}S{{O}_{4}}+2MnS{{O}_{4}}+3{{H}_{2}}O+5O $
The above reaction is balanced.
In case of $ {{H}_{2}}{{O}_{2}} $ :
 $ 5{{H}_{2}}{{O}_{2}}+5O\to 5{{H}_{2}}O+5{{O}_{2}} $
Thus, from the above reactions we get result as:
 $ 2KMn{{O}_{4}}+3{{H}_{2}}S{{O}_{4}}+5{{H}_{2}}{{O}_{2}}\to {{K}_{2}}S{{O}_{4}}+2MnS{{O}_{4}}+8{{H}_{2}}O+5{{O}_{2}} $
So,
2moles of $ KMn{{O}_{4}} $ requires 5 moles of $ {{H}_{2}}{{O}_{2}} $ .
Therefore, 1 mole of $ KMn{{O}_{4}} $ , will require 5/2 moles of $ {{H}_{2}}{{O}_{2}} $ .
So, we need to see from the above options, and select the correct value.
Thus, the correct answer is option C.

Note
A redox reaction can be defined as a chemical reaction in which electrons are transferred between two reactants participating in it. This transfer of electrons can be identified by observing the changes in the oxidation states of the reacting species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron. The formation of hydrogen fluoride is an example of a redox reaction. We can break the reaction down to analyse the oxidation and reduction of reactants. In redox reactions, energy is released when an electron loses potential energy as a result of the transfer. Electrons have more potential energy when they are associated with less electronegative atoms, and less potential energy when they are associated with a more electronegative atom.
A few examples of redox reactions in everyday life are discussed in terms of photosynthesis, decay, respiration, biological processes, corrosion/rusting, combustion and batteries. produced as fuel for its metabolic process. The reaction of photosynthesis is sensitized by chlorophyll.