3 SnSO4 + 2 K2CrO4 + 8 H2SO4 → 3 Sn(SO4)2 + Cr2(SO4)3 + 2 K2SO4 + 8 H2O
This is an acid-base reaction (neutralization): K2CrO4 is a base, H2SO4 is an acid.
This is an oxidation-reduction (redox) reaction:
3 SnII - 6 e- → 3 SnIV (oxidation)
2 CrVI + 6 e- → 2 CrIII (reduction)
SnSO4 is a reducing agent, K2CrO4 is an oxidizing agent.