1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Thiosulfate Standardization via Iodate Titration

  1. Nov 21, 2012 #1
    1. The problem statement, all variables and given/known data
    How do I figure out the concentration of Thiosulfate in mol/L or g/L if I am only given the following:

    0.00167M Iodate (IO3-)
    10g of 0.00167M Iodate (IO3-) in Solution
    0.71266g of Thiosulfate necessary to titrate
    IO3- MW = 174.9027 g/mol
    Thiosulfate MW = 248.18 g/mol

    2. Relevant equations
    Molarity = moles/L
    IO3- + 8I- + 6H+ -----> 3I3- + 3H2O
    I3- + 2S2O3 -----> 3I- + S4O6

    3. The attempt at a solution
    Using 1g~1mL
    0.00167M IO3- * (0.01 L) * (3 mol I3 / 1 mol IO3) * (2 mol S2O3 / 1 mol I3) * (1 / 0.71266 mL) * (1000 mL / 1 L) = 0.1406M S2O32-
  2. jcsd
  3. Nov 22, 2012 #2


    User Avatar

    Staff: Mentor

    With the assumption 1g=1mL your result is correct.

    But: the density of 0.1406M sodium thiosulfate is not 1 g/mL, but 1.0163 g/mL. I am not convinced you are expected to use this number, but it definitely shows your final result is wrong by about 1.6%.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook