Question

When H₂S gas is passed through acidified K₂Cr₂O₇ solution, the colour of the solution changes to ______.

Options

• green

• orange

• black

• red

Answer 1

When H₂S gas is passed through acidified K₂Cr₂O₇ solution, the colour of the solution changes to green.

Explanation:

H₂S is a reducing agent and reduces dichromate (Cr(VI), orange) to Cr(III) (green). Elemental sulfur is also formed as a fine (milky/yellow) precipitate.