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Question 32

From Chemistry HL Paper 1 (May 2024, TZ2)

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  1. Which of the following occurs during the Winkler test used to determine the concentration of dissolved oxygen in water?
    Step I: 2Mn2+(aq) + O2(g) + 4OH−(aq) → 2MnO2(s) + 2H2O(l)
    Step II: MnO2(s) + 2I−(aq) + 4H+(aq) → Mn2+(aq) + I2(aq) + 2H2O(l)
    Step III: 2S2O32−(aq) + I2(aq) → 2I−(aq) + S4O62−(aq)