Thiosulfate Standardization via Iodate Titration

[belyzel4]

Homework Statement

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

Homework Equations

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

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-

 

[Borek]

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%.