Phosphorus has three allotropic forms:
$(i)$ white phosphorus
$(ii)$ red phosphorus and
$(iii)$ black phosphorus.
Write the difference between white and red phosphorus on the basis of their structure and reactivity.

On heating with concentrated $NaOH$ solution in an inert atmosphere of $CO_{2}$,white phosphorus gives a gas. Which of the following statements is incorrect about the gas?

$A$ metal $(X)$ dissolves in both dilute $HCl$ and dilute $NaOH$ to liberate $H_2$ gas. Addition of $NH_4Cl$ and excess $NH_4OH$ to an $HCl$ solution of $(X)$ produces $(Y)$ as a precipitate. $(Y)$ is also produced by adding $NH_4Cl$ to the $NaOH$ solution of $(X)$. The species $(X)$ and $(Y)$,respectively,are:

The number of $P-OH$ bonds and the oxidation state of the phosphorus atom in pyrophosphoric acid $(H_4P_2O_7)$ respectively are

$FeSO_4$ forms a brown ring with which of the following?

Which of the following does not give oxygen on heating?