Which of the following oxides of nitrogen is neutral?

$PCl_{5} + P_{4}O_{10} \xrightarrow{\Delta } X$. The product $(X)$ is an oxygen-containing compound. How many moles of an oxyacid are formed on the complete hydrolysis of $1 \text{ mole}$ of $(X)$?

Which one of the following statements is not correct regarding phosphine?

Which among the following oxides is acidic in nature?

With which of the following does $FeSO_4$ form a brown ring?

Which among the following group-$15$ elements forms hydrogen bonding in its hydride compounds?