Question

When one mole of $Cl{O}_3^{-}$ changes to $C{l}^{-}$
A. It gains six electrons per mole
B. It gains four electrons per mole
C. It losses six electrons per mole
D. It gains three electrons per mole

Answer 1

Hint: If a chemical is going to accept the electrons, then the oxidation state of the chemical is going to decrease and if a chemical is going to lose the electrons, then the oxidation state of the chemical is going to increase.

Complete answer:
 - In the question it is given to calculate the number of electrons that are going to change when $Cl{O}_3^{-}$ changes to $C{l}^{-}$ .
- We have to calculate the oxidation state of the chlorine in both the chemicals ($Cl{O}_3^{-}$ and $C{l}^{-}$ ) to know the number of electrons going to gain or lose during the given chemical reaction.
- The oxidation state of the chlorine in $Cl{O}_3^{-}$ is as follows.
X+3 (-2) = -1
X = 5
- Means the oxidation state of the chlorine in $Cl{O}_3^{-}$ is ‘+5’.
- The oxidation state of the chlorine in $C{l}^{-}$ is as follows.
X = -1.
- Means the oxidation state of the chlorine in $C{l}^{-}$ is ‘-1’.
- So, the oxidation state of the chlorine is going to change from ‘5’ to ‘-1’.
- Means 6 electrons are going to be accepted by the one mole of the $Cl{O}_3^{-}$ .

So, the correct option is A.

Note:
By finding the change in the oxidation state of the element after the chemical reaction is going to help to find the number of electrons gained or lost during the chemical reaction by a particular chemical.