The Iodine "Clock Reaction" Involves the Following Sequence of Reactions

question 7

Multiple Choice

The iodine "clock reaction" involves the following sequence of reactions occurring in a reaction mixture in a single beaker.
1) IO₃^-(aq) + 5I^-(aq) + 6H⁺(aq)  3I₂(aq) + 3H₂O(l)
2) I₂(aq) + 2S₂O₃^2-(aq)  2I^-(aq) + S₄O₆^2-(aq)
The molecular iodine (I₂) formed in reaction 1 is immediately used up in reaction 2, so that no iodine accumulates. What is the overall reaction occurring in this experiment?

• A)IO₃^-(aq) + 3I^-(aq) + 2S₂O₃^2-(aq) + 6H⁺(aq)  2I₂(aq) + S₄O₆^2-(aq) + 3H₂O(l)
• B)IO₃^-(aq) + 4S₂O₃^2-(aq) + 6H⁺(aq)  I^-(aq) + 2S₄O₆^2-(aq) + 3H₂O(l)
• C)IO₃^-(aq) + 6S₂O₃^2-(aq) + 6H⁺(aq)  I^-(aq) + 3S₄O₆^2-(aq) + 3H₂O(l)
• D)IO₃^-(aq) + I₂(aq) + 8S₂O₃^2-(aq) + 6H⁺(aq)  3I^-(aq) + 4S₄O₆^2-(aq) + 3H₂O(l)
• E)IO₃^-(aq) + 2I₂(aq) + 6S₂O₃^2-(aq) + 6H⁺(aq)  5I^-(aq) + 3S₄O₆^2-(aq) + 3H₂O(l)

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