Here's why:
* Strong acids completely ionize in solution, meaning they donate their proton (H+) very readily. This leaves behind their conjugate base, which is a very weak base.
* Weak acids only partially ionize in solution, meaning they hold on to their proton more tightly. This means their conjugate base is a stronger base.
Since HNO3 is a strong acid, its conjugate base NO3- is a very weak base. It does not have any acidic properties.
