How is nitric acid manufactured by Ostwald's process ? How does it react with the following ?
`P_(4)`

Explanation

Ostwald's process : Ammonia, mixed with air in 1 : 7 or 1 : 8, when passed over a hot platinum gauze catalyst, is oxidised to NO mostly (about `95%`).
The reaction is
`4NH_(3)+5O_(2)underset(1155K)overset("Pt. gauze")to4NO+6H_(2)O,DeltaH=-1275" kJ."`
The liberated heat keeps the catalyst hot. The 'NO' is cooled and is mixed with oxygen to give the dioxide, in large empty towers (oxidation chamber). The product is then passed in to warm water, under pressure in the presence of excess of air, to give `"HNO"_(3)`.
`4NO_(2)+O_(2)+2H_(2)Oto4HNO_(3).`
The acid formed is about `61%` concentrated.
`P_(4)` reacts with conc. nitric acid to form phosphoric acid and `"NO"_(2)` gas.
`P_(4)+20" HNO"_(3)to4" H"_(3)"PO"_(4)+20" NO"_(2)+4" H"_(2)"O"`