White Phosphorus on reaction with concentrated NaOH solution in an inert atmosphere of CO₂ gives phosphine and compound (X). (X) on acidification with HCl gives compound (Y). The basicity of compound (Y) is :

The number of bonds between sulphur and oxygen atoms in S₂O₈^2- and the number of bonds between sulphur and sulphur atoms in rhombic sulphur, respectively, are :

In the following reaction, products (A) and (B) respectively, are :

NaOH + Cl₂ $$ \to $$ (A) + side products
(hot and conc.)

Ca(OH)₂ + Cl₂ $$ \to $$ (B) + side products (dry)

The C–C bond length is maximum in :