$A$ pale yellow solid molecule $(A)$ having crown shape is heated with conc. $H_2SO_4$. It gives a suffocating smell of gas $(B)$,which when passed through starch iodate paper,turns it blue. The gas $(B)$ is:

Explain the preparation of ozone. Explain the properties of ozone and state its uses.

Given below are two statements:
Statement $I$: The boiling point of hydrides of Group $16$ elements follows the order
$H_2O > H_2Te > H_2Se > H_2S$.
Statement $II$: On the basis of molecular mass,$H_2O$ is expected to have a lower boiling point than the other members of the group,but due to the presence of extensive $H$-bonding in $H_2O$,it has a higher boiling point.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following formulas represents fuming sulfuric acid (oleum)?

Which of the following statements regarding ozone $(O_3)$ is not correct?

Assertion : Reaction of $SO_2$ and $H_2S$ in the presence of $Fe_2O_3$ catalyst gives elemental sulphur.
Reason : $SO_2$ is a reducing agent.