The amount of I−3(aq) in a solution can be determined by titration with a solution containing a known concentration of S2O2−3(aq)
(thiosulfate ion). The determination is based on the net ionic equation

2S2O2−3(aq)+I−3(aq)⟶S4O2−6(aq)+3I−( aq)

Given that it requires 35.1 mL
of 0.420 M Na2S2O3(aq)
to titrate a 25.0 mL
sample of I−3(aq),
calculate the molarity of I−3(aq)
in the solution.