Rhombic sulphur has the following structure:

$SO_2$ can be converted into $SO_3$ with the help of:

When $H_2S$ gas is passed through nitric acid,the product is

When oxygen is passed through a solution of $Na_2SO_3$,we get:

The number of $S=O$ and $S-OH$ bonds present in peroxodisulphuric acid $(H_2S_2O_8)$ and pyrosulphuric acid $(H_2S_2O_7)$ respectively are:

When $SO_2$ is passed through cupric chloride $(CuCl_2)$ solution,what is the observation?