How does the acidity of pentoxides vary down the $VA$ group?

Which of the following metals produces nitrous oxide $(N_2O)$ when reacted with dilute $HNO_3$?

In which of the following options are the product gases $X$ and $Y$ (other than water vapour) the same?

$8 NH_{3} + 3 Cl_{2} \rightarrow X$ (Excess $NH_{3}$)
$NH_{3} + 3 Cl_{2} \rightarrow Y$ (Excess $Cl_{2}$)
What are $X$ and $Y$ in the above reactions?

Hydrolysis of $PCl_5$ gives

Which of the following is used in the industrial production of nitric acid by the Ostwald process?