why is benzene inert towards most the oxidicing agents?also mention the nitrating mixture used to nitrate benzene.

In benzene, the p orbitals of the carbon atoms above and below the plane of the molecule overlap sideways with each other. This means that 6 pi electrons are found in a delocalised electron cloud above and below the plane of the molecule. This is represented by a ring in the displayed formula.

However, because the electrons are spread out across the molecule, the overall electron density is less than that of a conventional double bond. 

Oxidising agents, like KMnO₄ reacts with localized pi bonds as in alkenes and alkynes, in benzene there are delocalized pi bonds (pi electronic cloud) so KMnO₄ can not react.

 

 

The nitrating mixture is H2SO4 + HNO3