$A$ colourless gas with the smell of rotten fish is

What are the number of $P - O - P$ bridges in phosphorus pentoxide $(P_4O_{10})$ and phosphorus trioxide $(P_4O_6)$ respectively?

Consider the following Assertion $(A)$: Phosphorus can form both phosphorus$(III)$ and phosphorus$(V)$ chlorides, but nitrogen cannot form nitrogen$(V)$ chloride. Reason $(R)$: The electronegativity of nitrogen is more than that of phosphorus. The correct answer is

$FeSO_4$ gives a brown ring with ........

When concentrated $H_2SO_4$ is heated with $KNO_3$,brown fumes are evolved. These fumes are due to:

Phosphorus can be stored in