Under which conditions can active nitrogen be obtained from $N_2$ gas using an electric spark?

$PCl_{5} + P_{4}O_{10} \xrightarrow{\Delta } X$. 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 $(X)$?

During which of the following processes is phosphine $(PH_3)$ $NOT$ obtained?

Which compound is used in smoke screens?

$P_4 + 3NaOH + 3H_2O \to A + 3NaH_2PO_2$. Here,$A$ is:

Two oxides of nitrogen, $NO$ and $NO_2$, react together at $253 \ K$ to form a compound of nitrogen $X$. $X$ reacts with water to yield another compound of nitrogen $Y$. The shape of the anion of $Y$ is: