Question

Fill in the blank.
____________ is a commonly used chemical method to purify water.
A) Chlorination
B) Fluorination
C) Bromination
D) Boiling

Answer 1

As we know that in the 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 symbols of fluorine, chlorine, bromine and iodine are ${\text{f,Cl}}{\text{.Br and I}}$ respectively.

Complete answer:
We must have to remember that chlorination is a commonly used chemical method to purify water. The molecular molecule of chlorine is $C{l_2}$. The molecular formula of water is ${H_2}O$. Chlorine is used to kill bacteria and viruses of the microorganisms.
According to the above discussion, we conclude chlorination is a commonly used chemical method to purify water.
Hence, option A is the correct answer. Because chlorination is a commonly used chemical method to purify water.
The option B is not the correct answer. Because fluorination is not a commonly used chemical method to purify water.
The option C is not the correct answer. Because bromination is not a commonly used chemical method to purify water.
The option D is not the correct answer. Because boiling is not a commonly used chemical method to purify water.

Hence, option A is the correct answer.

Note:
We need to know that the 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. The symbol of $X$is used for an element; there are fluorine, chlorine, iodine and bromine in the chemical reaction.