Question

Na2CrO4-->Na2Cr2O7-->Cr2(SO4)3-->Cr(OH)3-->K[Cr(OH)4(H2O)2]

Answer 1

2Na2CrO4+H2SO4=Na2Cr2O7+Na2SO4+H2O
Na2Cr2O7+3Na2S+7H2SO4=Cr2(SO4)3+3S+4Na2SO4+7H2O
Cr2(SO4)3+6NaOH=2Cr(OH)3+3Na2SO4
Cr(OH)3+KOH+2H2O=K[Cr(OH)4(H2O)2]