Question

In aqueous alkaline solution, two electrons reduction of $H{O_2}^ - $ gives:
A. $H{O^ - }$
B. ${H_2}O$
C. ${O_2}$
D. ${O_2}^ - $

Answer 1

Hint: We can define oxidation and reduction reactions in terms of addition (or) removal of oxygen, hydrogen and electrons to a compound.

Complete step by step answer:
In terms of transfer of hydrogen, we can say loss of hydrogen is oxidation and gain of hydrogen is reduction.
In terms of transfer of oxygen, we can say loss of oxygen is reduction and gain of oxygen is oxidation.
With the respect to transfer of electrons, loss of electrons is oxidation and gain of electrons is reduction.
Hydrogen peroxide dissociates into hydrogen ion and dioxidanide ion $H{O_2}^ - $.
${H_2}{O_2} \to {H^ + } + H{O_2}^ - $
We can write $H{O_2}^ - $ as $HOO$ anion.
The two electron reduction of $H{O_2}^ - $ in an aqueous alkaline solution, we get the product $H{O^ - }$. We can write the equation as,
$H{O_2}^ - + {H_2}O + 2{e^ - } \to O{H^ - }$
The reaction is unbalanced. We need three moles of $O{H^ - }$ in the product side to make the reaction a balanced one. We write the balanced equation is,
$H{O_2}^ - + {H_2}O + 2{e^ - } \to 3O{H^ - }$
The oxidation state of oxygen in $O{H^ - }$ is $ - 2$.
The oxidation state of oxygen in $H{O_2}^ - $ is $ - 1$.
Oxidizing agents are those species (molecule/ion) that accept electrons and reducing agents are those species (molecule/ion) that donate electrons. A substance that is oxidized acts as a reducing agent and substance that is reduced acts as an oxidizing agent.

Therefore, the option A is correct.

Note:
We can define redox reactions as chemical reactions in which transfer of electrons takes place between two reactants. We can recognize the electron transfer by observing the change in oxidation states of the species that are reacting. Batteries (or) electrochemical cells, respiration, photosynthesis, combustion, rusting are some examples of redox reactions.