White phosphorus reacts with sulphuryl chloride to form $PCl_5$ and $X$. Chlorine reacts with $X$ in the presence of wood charcoal to form $Y$. $X$ and $Y$ are respectively

Which among the following $P$-block elements forms a colourless and odourless hydride?

Why is a Tyndall box used in the manufacture of sulfuric acid by the contact process?

Assertion : There is a large difference between the melting and boiling points of $O$ and $S$.
Reason : It can be explained on the basis of their atomicity in $O_2$ and $S_8$ molecules.

Identify the correct statements from the following:
$i$. Sulphuric acid is manufactured by contact process.
$ii$. $SO_3$ dissolves in $H_2SO_4$ to form pyrosulphuric acid $(H_2S_2O_7)$.
$iii$. $H_2SO_4$ is used in the manufacture of fertilisers such as ammonium sulphate and super phosphate.
$iv$. In the reaction,$S + 2H_2SO_4 (\text{conc.}) \longrightarrow 3SO_2 + 2H_2O$,$H_2SO_4$ is oxidised to $SO_2$.

What happens when:
$(i)$ Concentrated $H_2SO_4$ is added to calcium fluoride
$(ii)$ $SO_3$ is passed through water?