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Reaction Mechanism for iodide and peroxodisulfate Watch

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    Hi Guys,

    I've worked out the order of both reactants as first order.

    The reactions are:

    1) S2O82- (aq) + 2I- (aq) --> 2SO42- (aq) + I2 (aq)
    2) 2S2O32- (aq) + I2 (aq) --> S4O62- (aq) + 2I- (aq)

    And I know the RDS lies within reaction 1 – otherwise the reaction wouldn’t work, as no iodine would be produced. However, there must be another step, as 2 moles of I- can’t be used...

    I NEED URGENT HELP PLEASE!
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    possibilities for 1st order for iodide that i have found are

    from HERE

    S2O8^-2 +I- --> SO4^2- +SO4I- slow rate determining step
    SO4I- + I- --> SO4^2- +I2 fast

    OR FROM HERE

    I- + S2O8 2- --> *[I...S2O8]3- SLOW RDS

    *[I...S2O8]3- + I- --> I2 + 2 SO4 2-
 
 
 
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