The commercial name of peroxydisulphuric acid is:

Which of the following compounds has a peroxide linkage?

Given below are two statements:
Statement $I$: The boiling points of the following hydrides of group $16$ elements increase in the order: $H_2O < H_2S < H_2Se < H_2Te$.
Statement $II$: The boiling points of these hydrides increase with an increase in molar mass.
In the light of the above statements,choose the most appropriate answer from the options given below:

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

Write the order of thermal stability of the hydrides of Group $16$ elements.

$H_2S$ is less acidic than $H_2Te$. Why?