Question

Assertion: Fluorine oxidises water to oxygen whereas chlorine and bromine react with water to form corresponding hydrohalic and hypohalous acid.
Reason: The reactivity of halogens increases down the group.
A.Both assertion and reason are correct and reason is the correct explanation for Assertion.
B.Both assertion and reason are correct and reason is not the correct explanation for Assertion.
C.Assertion is correct but reason is incorrect.
D.Both assertion and reason are incorrect.

Answer 1

Hint: We know that fluorine is the most electronegative element of the periodic table. All the halogens belong to group number \[17\]. The name used for group number \[17\] is halogens family.

Complete answer:
We know that electronegativity of the elements decreases down the group. As we go down the group, atomic size increases, thus electronegativity decreases. Thus the order of electronegativity in group number \[17\] is shown below:
\[{\text{F}} > {\text{Cl}} > {\text{Br}} > {\text{I}}\]
Group number \[17\] is also known as halogens. It is also called the halogen family.
When fluorine reacts with water, hydrogen fluoride and oxygen are formed. The following reaction is shown below:
\[2{{\text{F}}_2} + {{\text{H}}_2}{\text{O}} \to 4{\text{HF}} + {{\text{O}}_2}\]
When chlorine reacts with water, hydrogen chloride and hypohalous acid is formed. The reaction of the chlorine with oxygen is shown below:
\[{\text{C}}{{\text{l}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{HCl}} + {\text{HOCl}}\]
When bromine reacts with water, hydrogen bromide and hypohalous acid is formed. The reaction of the bromine with oxygen is shown below:
\[{\text{B}}{{\text{r}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{HBr}} + {\text{HOBr}}\]
Thus, fluorine oxidises water to oxygen whereas chlorine and bromine react with water to form corresponding hydrohalic and hypohalous acid.

Additional information:
Other halogens like chlorine, bromine, iodine except for fluorine are able to show variable oxidation state due to the presence of vacant d orbitals.
Due to the small size of the fluorine atom, it is the most electronegative atom and due to this it is not able to show variable oxidation state and only able to show one oxidation state.
Thus, the assertion is true but the explanation is not the correct reason for assertion.

Note:
Keep in mind that fluorine is the most electronegative and fluorine does not have vacant d orbital, thus it is only able to show \[ + 1\] oxidation state and unable to show variable oxidation state like other halogens.