What is the molarity of a potassium triiodide solution, KI3(aq), if 30.00 mL of the solution is required to completely react with 25.00 mL of a 0.500 M thiosulfate solution, K2S2O3(aq)? The chemical equation for the reaction is 2 S2O32-(aq) + I3-(aq) → S4O62-(aq) + 3 I-(aq)?
a. 0.167 m
b. 0.333 m
c. 0.120 m
d. 0.0833 m

molarity=0.21M

Explanation:

First write the balance chemical equation:

Calculate the oxidation number of each element both side:

Reactant sideoxidaion number:

product side oxidation number:

this is change in oxidaion numbe rper atom

oxidaion number per molecule=3×(2\3)=2

n-factor of =2

.................................1

For thiosulfae solution:

Normality of thiosulfate solution=0.5

lets N1 and N2 are the normality of thiosulfate solution and potassium triiodide solution respectively

lets V1 and V2 are the volume of thiosulfate solution and potassium triiodide solution respectively

=0.5

=25ml

=?

=30ml

on putting all the value

=0.42 normality of potassium triiodide

molarity=0.42/2=0.21M

molarity=0.21M

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