Nitrogen forms how many oxides?

Which of the following is the correct order of bond angles in the given hydrides?

The maximum number of $P-H$ bonds is present in a molecule of:

Which product is formed by the reaction of $Zn$ with cold and very dilute $HNO_3$?

Which of the following pentahalides is not possible?

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 $P_3O_9^{3-}$?