Select the correct statement.

What is obtained by the reaction of concentrated $H_2SO_4$ with $PCl_5$?

Identify the method used to obtain $SO_2$ gas in industry.

How many total statements are correct in the following?
$(i)$ $SO_2$ - antichlor,preservative
$(ii)$ $O_3$ - Disinfectant
$(iii)$ $Cl_2$ - Antiseptic
$(iv)$ $O_2$ - used in oxy-acetylene welding
$(v)$ $PH_3$ - used in smoke screens
$(vi)$ $HNO_3$ - Pickling of stainless steel

The most efficient agent for the absorption of $SO_3$ is

Explain the oxoacids of sulfur.