6 Fe(OH)2 + K2Cr2O7 + 13 H2SO4 → Cr2(SO4)3 + 3 Fe2(SO4)3 + K2SO4 + 19 H2O
This is an acid-base reaction (neutralization): Fe(OH)2 is a base, H2SO4 is an acid.
This is an oxidation-reduction (redox) reaction:
6 FeII - 6 e- → 6 FeIII (oxidation)
2 CrVI + 6 e- → 2 CrIII (reduction)
Fe(OH)2 is a reducing agent, K2Cr2O7 is an oxidizing agent.