MDCAT Chemistry MCQ #5424

When sulfur dioxide gas is passed through an acidified solution of potassium dichromate, the orange color changes to green. What is the chemical basis for this change?

MDCAT Chemistry MCQ #5424

  1. Question 1

    Q1. When sulfur dioxide gas is passed through an acidified solution of potassium dichromate, the orange color changes to green. What is the chemical basis for this change?

    • A) It oxidizes the potassium ions to metal
    • B) It reduces the dichromate to yellow chromate
    • C) It reduces Cr(VI) to green Cr(III) ions
    • D) It dehydrates the dichromate to chromium trioxide

    Answer: It reduces Cr(VI) to green Cr(III) ions

    Explanation: Sulfur dioxide is a reducing agent that reduces Cr(VI) in K2Cr2O7 to green Cr(III) in Cr2(SO4)3; KMnO4 would turn colorless, not green.