Which of the following can be used as an anesthetic?

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

Which of the following produces $NO_2$ gas on heating?

Which gas is produced in the atmosphere due to lightning?

Which of the following is not hydrolysed?

The passivity of iron in concentrated nitric acid is due to