White silver surface turns black when $O_3$ is passed over it. This is due to the formation of

Among the hydrides of group $16$ elements,the hydride $X$ has the lowest boiling point and the hydride $Y$ has the highest boiling point. $X$ and $Y$ respectively are:

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 $SO_2$.

Which of the elements listed below occurs in allotropic forms?

Peroxymonosulfuric acid is known as ..........

Which of the following compounds undergoes hydrolysis easily?