Orthophosphorus acid on disproportionation gives $PH_3$ and another oxoacid of phosphorus '$X$'. The basicity of $X$ is

What are the products obtained when ammonia is reacted with excess chlorine?

Which of the following molecules contains the highest number of $P-H$ bonds?

Which gas is evolved when ammonium dichromate is heated?

Cyclic polymetaphosphates have the general formula of $[P_nO_{3n}]^{n-}$. Cyclic trimeric polymetaphosphate $(P_3O_9)^{3-}$ has commercial importance. Which of the following is not true regarding $P_3O_9^{3-}$?