Sum of $$\pi$$-bonds present in peroxodisulphuric acid and pyrosulphuric acid is ___________

Consider the following sulphur based oxoacids.

$$\mathrm{H}_{2} \mathrm{SO}_{3}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{H}_{2} \mathrm{S}_{2} \mathrm{O}_{8}$$ and $$\mathrm{H}_{2}\mathrm{S}_{2} \mathrm{O}_{7}$$.

Amongst these oxoacids, the number of those with peroxo $$(\mathrm{O}-\mathrm{O})$$ bond is ________.

The number of non-ionisable protons present in the product B obtained from the following reactions is ___________.

$$ \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+\mathrm{PCl}_{3} \rightarrow \mathrm{C}_{2} {\mathrm{H}_{5} \mathrm{Cl}+\mathrm{A}} $$

$$\mathrm{A}\,{+}\, \mathrm{PCl}_{3} \rightarrow \mathrm{B}$$

Consider the following reactions:

PCl₃ + H₂O $$\to$$ A + HCl

A + H₂O $$\to$$ B + HCl

The number of ionisable protons present in the product B is _______________.