Question

what is the oxidation state of nitrogen in pernitric acid

Answer 1

Oxidation Number        Nitrogen Compound         PhosphorusCompound      

1)  +3                          HNO2 (nitrous acid)     H3PO3 (phosphorousacid)  
2) +3                          N2O3                                  P4O6


 3) +5                         HNO3 (nitric acid)        H3PO4 (phosphoric acid)   


4)   +5                     NaNO3 (sodium nitrate)   Na3PO4 (sodium phosphate)

Answer 2

pernitric acid i.e. HNO4
oxidation state of N=-1+8=7 but this is exceed the highest o.s of N =+5
so here nitrogen oxidation state we consider by their structure

O=N=O here we see o.s of N=+5
|O--O--H

so +5 oxidation state of nitrogen in pernitric acid