Question

When $C{l_2}$ gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from:
A) Zero to $- 1$ and zero to$- 3$
B) Zero to $+ 1$ and zero to $- 3$
C) Zero to $+ 1$ and zero to $-5$
D) Zero to $- 1$ and zero to$+ 5$

Answer 1

As we know that in a periodic table totally 118 elements are present now. In the periodic table there are eighteen groups and seven periods. In the periodic table the seventeenth group is the halogen group. In this group, four elements are only considered as halogen out of five elements in the column. There are fluorine, chlorine, bromine and iodine considered as halogen in the modern periodic table. The atomic number of chlorine atoms is $17$. The mass number of chlorine atoms is $35$. The symbol of chlorine atoms is $Cl$.

Complete answer:
We need to know that the chemical formula of chlorine molecules is $C{l_2}$. It is diatomic in nature.
The oxidation state of chlorine atoms in chlorine molecules is zero.
When chlorine gas is reacted with hot and concentrated sodium hydroxide solution to give the product of sodium chloride and hypochlorite.
The chemical reaction for the above discussion is given below,
$C{l_2} + NaOH \to NaCl + HOCl$
The oxidation number of chlorine changes from chlorine molecule to sodium chloride is zero to$- 1$and the oxidation number of chlorine changes from chlorine molecule to hypochlorite is zero to $- 3$
According to the above discussion, we conclude when $C{l_2}$gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from Zero to $- 1$ and zero to$- 3$.

Hence, option A is the correct answer.

Note:
We have to know that halogen is the most electron affinity group in the periodic table. Halogen is also the most electronegativity group in the periodic table. The ionisation energy of the halogen is very less compared to other groups. In halogen from top to bottom, electron affinity decreases. Chlorine is the highest electron affinity species in the periodic table, because the size of the fluorine is very small compared to chlorine. But, the electronegativity value of fluorine is high compared to the electronegativity value of chlorine.