In the electrothermal process,the compound displaced by silica from calcium phosphate is

The compound$(s)$ which generate$(s)$ $N_2$ gas upon thermal decomposition below $300^{\circ} C$ is (are)
$(A)$ $NH_4 NO_3$
$(B)$ $(NH_4)_2 Cr_2 O_7$
$(C)$ $Ba(N_3)_2$
$(D)$ $Mg_3 N_2$

Among the following,cyclic species are :
$I$. $H_5P_3O_{10}$ $II$. $[B_3O_3(OH)_5]^{2-}$ $III$. $H_5P_5O_{15}$ $IV$. $P_3N_3Cl_6$

Aluminium is usually found in $+3$ oxidation state. In contrast,thallium exists in $+1$ and $+3$ oxidation states. This is due to

The purest form of $N_2$ is prepared by the thermal decomposition of:

When tin is treated with concentrated nitric acid,what is the product formed?