Which gas is used in the manufacturing of nitrogenous fertilizers?

The stable bivalency of $Pb$ and trivalency of $Bi$ is

In which of the following acids,$P-P$ bond is present?

$NO_2$ is a mixed oxide. This is proved by the fact that it reacts with $H_2O$ and then with $NaOH$ to form:

Which of the following are the correct orders of stability of oxidation states of cations?
$(a) \ Pb^{+2} > Pb^{+4}, Tl^{+1} < Tl^{+3}$
$(b) \ Bi^{+3} < Sb^{+3}, Sn^{+2} < Sn^{+4}$
$(c) \ Pb^{+2} > Pb^{+4}, Bi^{+3} > Bi^{+5}$
$(d) \ Tl^{+3} < In^{+3}, Sn^{+2} > Sn^{+4}$
$(e) \ Sn^{+2} < Pb^{+2}, Sn^{+4} > Pb^{+4}$
$(f) \ Sn^{+2} < Pb^{+2}, Sn^{+4} < Pb^{+4}$

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} $
$(5)$ $HNO_3 + P_4O_{10} \to$
$(6)$ $P_4 + HNO_3 \to$