QQuestion
What colour is produced when H₂S gas is passed through a solution of potassium dichromate acidified with dilute sulphuric acid?
(a) Orange
(b) Violet
(c) Green
(d) Deep blue
✓Answer
(c) Green
Explanation
Hydrogen sulphide (H₂S) acts as a reducing agent. When it is passed through acidified potassium dichromate (K₂Cr₂O₇) solution, the orange-coloured dichromate ions (Cr₂O₇²⁻) are reduced to green-coloured chromium(III) ions (Cr³⁺).
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