Question

In the below reaction:
${{\text{I}}_{\text{2}}}{\text{ + KI}} \to {\text{K}}{{\text{I}}_{\text{3}}}$
A.Only oxidation takes place
B.Only reduction takes place
C.Both the above
D.None of the above

Answer 1

Hint: Oxidation: The compound which loses the electron during the reaction or the compound whose oxidation number increases during the reaction.
Reduction: The compound which gains the electron during the reaction or the compound whose oxidation number decreases during the reaction.

Complete step by step solution:
Generally the compound whose oxidation number increases during the reaction is known as oxidised compound and the compound whose oxidation number decreases during the reaction is known as reduced compound.
Now let us first talk about the oxidations number of elements in the compounds given in the reaction.
Oxidation number of an element: It is defined as the total number of electrons that an atom accepts or loses in order to make a chemical bond which results in the formation of a chemical compound.
Oxidation: The compound which loses the electron during the reaction or the compound whose oxidation number increases during the reaction.
Reduction: The compound which gains the electron during the reaction or the compound whose oxidation number decreases during the reaction.
Here in the reaction ${{\text{I}}_{\text{2}}}{\text{ + KI}} \to {\text{K}}{{\text{I}}_{\text{3}}}$ the oxidation number of iodine in ${I_2}$ is $0$, oxidation number of iodine in $KI$ is $ - 1$ and in $K{I_3}$ the oxidation number of ${I_3}^ - $ is $1$. Therefore ${I_2}$ is reduced and $KI$ is oxidised to $KI{O_3}$.
There is another definition of defining oxidised and reduced compounds as well.
Oxidized compound: The compound to which oxygen is added during the reaction, is known as oxidized compound.
Reduced compound: The compound from which oxygen is removed during the reaction, is known as reduced compound.

Hence, the option C is correct.

Note: Generally the compound which is oxidised in the reaction will act as reducing reagent (which oxidise the other compounds) and the compound which is reduced in the reaction will act as oxidising reagent (which reduce the other compounds) for the reaction.