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Choose the correct option.
When H₂S gas is passed through acidified K₂Cr₂O₇ solution, the colour of the solution changes to:
When $\text{H}_2\text{S}$ gas is passed through acidified $\text{K}_2\text{Cr}_2\text{O}_7$ solution, the colour of the solution changes to:
- (a)green.
- (b)orange.
- (c)black.
- (d)red.
Answer
Answer
Correct option: (a)
Answer: (a) green.
Acidified potassium dichromate is reduced by $\text{H}_2\text{S}$ from orange dichromate ion ($\text{Cr}_2\text{O}_7^{2-}$) to green chromium(III) ion ($\text{Cr}^{3+}$), while $\text{H}_2\text{S}$ is oxidized to colloidal sulfur.