NITRIC acid with water reacts as follows: HNO3 + H2O ⇌ H3O+ + NO3−
Nitric acid is a relatively strong acid, MEANING it tends to ionize almost completely in aqueous solution.
H2 ACTS as a base to abstract an H+ from the nitric acid. The resulting H3O+, hydronium, is the conjugate acid, while the NO3-, nitrate, is the conjugate base (this is the molecule of nitric acid, but STRIPPED of its H+.