K2Cr2VIO7 + 3 Na2SIVO3 + 4 H2SVIO4 Cr2III(SVIO4)3 + K2SVIO4 + 3 Na2SVIO4 + 4 H2O

This is an acid-base reaction (neutralization): Na2SO3 is a base, H2SO4 is an acid.

This is an oxidation-reduction (redox) reaction:

3 SIV - 6 e- 3 SVI (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

Change the oxidation states