Explain why fluorine forms only one oxoacid,$HOF$.

Which among the following hydrogen halides is thermally least stable?

Name two poisonous gases which can be prepared from chlorine gas.

Compound $A$ and $B$ respectively are :-
$Cl_2 + 2NaOH (cold \& dil.) \rightarrow A + NaCl + H_2O$
$3Cl_2 + 6NaOH (hot \& conc.) \rightarrow B + 5NaCl + 3H_2O$

Which of the following reactions are correct with respect to the formation of products?
$I$. $2 NaOH + SO_2 \longrightarrow Na_2SO_3 + H_2O$
$II$. $XeF_4 + O_2F_2 \stackrel{143 K}{\longrightarrow} XeF_6 + O_2$
$III$. $PCl_5 + 4 H_2O \longrightarrow H_3PO_4 + 5 HCl$
$IV$. $2 NaNO_2 + 2 HCl \longrightarrow 2 NaCl + NO + NO_2 + H_2O$

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ $ICl$ is more reactive than $I_{2}.$
Reason $(R):$ $I-Cl$ bond is weaker than $I-I$ bond.
In the light of the above statements,choose the most appropriate answer from the options given below: