Discussion Forum



1)

Acidified potassium dichromate is treated with hydrogen sulfide. In the reaction, the oxidation number of chromium


A) Increases from + 3 to +6

B) Decreases from+6 to+3

C) Remains unchanged

D) Decreases from +6 to +2

Answer:

Option B

Explanation:

Decreases from +6 to+3.

K2Cr2O7+ 4H2SO4 → K2SO4 + Cr2 (SO4 )3 + 4H2O + 3O [H2S + [O]→ S+H2O]×3

       +6                                                     +3

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