What happens when H2S is added to acidified potassium dichromate solution?

Answer: When hydrogen sulphide (H2S) is added to an orange solution of acidified potassium dichromate (K2Cr2O7), a green chloric salt is formed. As a result, the colour of the solution turns green. H2S is oxidized and sulfur is precipitated.

K2Cr2O7 + 4H2SO4 + 3H2S = K2SO4 + Cr2(SO4)3 + 7H2O + 3S ↓