Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of

Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it . This is due to the formation of Cr₂(SO₄)₃

${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+3{\mathrm{Na}}_2{\mathrm{SO}}_3+4{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3+{\mathrm{K}}_2{\mathrm{SO}}_4+3{\mathrm{Na}}_2{\mathrm{SO}}_4+4{\mathrm{H}}_2\mathrm{O}$