CrIIO + 2 HNVO3 CrVI(NIIIO3)2 + H2O

This is an oxidation-reduction (redox) reaction:

2 NV + 4 e- 2 NIII (reduction)

CrII - 4 e- CrVI (oxidation)

HNO3 is an oxidizing agent, CrO is a reducing agent.