The oxidation state of N in nitric acid (HNO3) is +5. This can be determined by considering the electronegativity of the atoms involved. Oxygen is more electronegative than nitrogen, so it attracts electrons more strongly. This means that the oxygen atoms in nitric acid pull electrons away from the nitrogen atom, giving it a positive oxidation state. The oxidation state of hydrogen is +1, and there are three oxygen atoms in nitric acid, each with an oxidation state of -2, so the overall charge of the molecule must be +1. This means that the oxidation state of nitrogen must be +5 in order to balance the charges.