HNO3   oxidizes NH4+ ions to nitrogen and itself gets reduced to NO2.The moles of HNO3 required by 1 mole of NH42SO4  is

HN+5O3 + N-3H4+→N02+N+4O2V.F.  of HNO3=5−4=1V.F.  of  NH4+=0−−3=3so  molar  ratio  of HNO3  and  NH4+  is 3 : 1.1 mole NH42SO4  is  found  to  contain  2  mole  of NH4+So,  required  moles  of  HNO3  is  3 ×  2=6  moles.