Question

Cr - Cr2O3 - Cr2(SO4)3 - Cr(OH)3 - Cr2O5 - Cr(NO3)3

Answer 1

4Cr + 3O2 = 2Cr2O3 ↑°
Cr2O3 + 3 H2SO4 = Cr2(SO4)3 + 3 H2O
Cr2(SO4)3 + 6NaOH = 2Cr(OH)3 + 6 H2O
Cr(OH)3 + 3 NaOH = Na3CrO3 + 3 H2O↑°