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Homework Help: Determine the rate of reaction with respect to I-

  1. Feb 7, 2012 #1
    1. The problem statement, all variables and given/known data
    -------Solution1:-----Solution2:-----Solution3:---------- Solution4:-----Solution5:--------------- Solution6:
    Exp. 0.200M KI-----2% starch-----0.020M Na2S2O3 -----water----0.050M acetate buffer -----0.40M H2O2

    1-----2.00mL ----- 1mL --------- 1.00mL ---------------5mL --------- 10mL ------------------ 1.00mL
    2-----4.00mL ----- 1mL --------- 1.00mL ---------------3mL --------- 10mL ------------------ 1.00mL
    3-----2.00mL ----- 1mL ---------1.00mL ----------- ---4mL --------- 10mL --------- --------- 2.00mL

    there were 3 experients and these were the recorded times:

    Ex.1 Trail1=166s

    Ex. 2 Trail1=48s

    Ex.3 Trail1=5s

    2. Relevant equations
    The information im given says that I- and S2O3^2- react in a 1:1 ratio resulting in Δ[I-]=ΔS2O3^2-]. How do i find the concentration of S2O3^2- when its not given? its not listed in the concentrations above, so do i have to calculate it from one of the concentrations and experiments above? if so, how would i do that?

    3. The attempt at a solution
    I know rateI=-Δ[S2O3^2-]/time
    Last edited: Feb 7, 2012
  2. jcsd
  3. Feb 7, 2012 #2


    User Avatar

    Staff: Mentor

    You know how much substance is present, you know total volume of the solution, you know everything you need to calculate the initial concentration. When everything is given, it is as if you were given the concentration itself.
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