6 NaI-I + 2 Na2CrVIO4 + 8 H2SO4 5 Na2SO4 + 3 I20 + Cr2III(SO4)3 + 8 H2O

This is an acid-base reaction (neutralization): Na2CrO4 is a base, H2SO4 is an acid.

This is an oxidation-reduction (redox) reaction:

6 I-I - 6 e- 6 I0 (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

Change the oxidation states