Which of the following elements does not show allotropy?

Ammonia on reaction with hypochlorite anion,can form

Which of the following reactions give phosphine $(PH_3)$?
$(i)$ Reaction of calcium phosphide with water
$(ii)$ Heating white phosphorus with concentrated $NaOH$ solution in an inert atmosphere
$(iii)$ Heating red phosphorus with alkali

$Ge(II)$ compounds are powerful reducing agents whereas $Pb(IV)$ compounds are strong oxidants. This can be attributed to:

Which of the following reactions is a part of the large-scale industrial preparation of nitric acid?

The dimerisation of $NO_2$ is accompanied with