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

An element $X$ belongs to group $16$ and $5^{th}$ period. Its atomic number is

Which one is known as oil of vitriol?

At what temperature does dioxygen gas liquefy and at what temperature does it freeze?

Given below are two statements $:$
Statement $I : H_2Se$ is more acidic than $H_2Te$.
Statement $II : H_2Se$ has higher bond enthalpy for dissociation than $H_2Te$.
In the light of the above statements,choose the correct answer from the options given below.

Write a short note on the anomalous behavior of oxygen.