$NH_3$ can not be obtained by

When orthophosphoric acid is heated to $600\,^oC$,it forms .................. .

Which one of the following compounds on strong heating evolves ammonia gas?

Illustrate how copper metal can give different products on reaction with $HNO_3$.

Find the correct statements related to group $15$ hydrides.
$A$. Reducing nature increases from $NH_3$ to $BiH_3$
$B$. Tendency to donate lone pair of electrons decreases from $NH_3$ to $BiH_3$
$C$. The stability of hydrides decreases from $NH_3$ to $BiH_3$
$D$. $HEH$ bond angle decreases from $NH_3$ to $SbH_3$ ($E$ = Elements of group $15$)
Choose the correct answer from the options given below:

The number of pentagons in $C_{60}$ and trigons (triangles) in white phosphorus,respectively,are