Nitric oxide $(NO)$ is prepared by the action of dilute $HNO_3$ on which of the following metals?

How many of the following reactions will form $PH_3$ gas?
$(1)$ $Ca_3P_2 + H_2O \to$
$(2)$ $H_3PO_3 \xrightarrow{\Delta} $
$(3)$ $P_4 + NaOH \to$
$(4)$ $H_3PO_4 \xrightarrow{\Delta} $
$(5)$ $HNO_3 + P_4O_{10} \to$
$(6)$ $P_4 + HNO_3 \to$

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

Phosphorous and phosphoric acids are, respectively, . . . . . . acids.

Nitrogen gas is liberated by thermal decomposition of

In the reaction $4HNO_3 + P_4O_{10} \to 4HPO_3 + x$,the product $x$ is