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 0.200 M thiosulfate solution,Na₂S₂O₃(aq) ? The chemical equation for the reaction is:
2 S₂O₃^2-(aq) + I₃^-(aq) → S₄O₆^2-(aq) + 3 I^-(aq)

Question

Quizplus · Accepted Answer

The balanced chemical equation is:2 S₂O₃^2-(aq)+ I₃^-(aq)→ S₄O₆^2-(aq)+ 3 I^-(aq)From the stoichiometry of the balanced chemical equation, we can see that 2 moles of S₂O₃^2- react with 1 mole of I₃^-. Therefore, the number of moles of I₃^- in 30.00 mL of the KI₃ solution is:$$moles\ of\ I_3^- = (25.00\ mL)(0.200\ M) imes \frac{1\ mol\ I_3^-}{2\ mol\ S_2O_3^{2-}} = 2.500 imes 10^{-3}\ mol$$The molarity of the KI₃ solution is:$$Molarity\ of\ KI_3 = \frac{moles\ of\ I_3^-}{volume\ of\ solution\ in\ liters} = \frac{2.500 imes 10^{-3}\ mol}{30.00 imes 10^{-3}\ L} = 0.0833\ M$$Therefore, the correct choice is A) 0.0833 M.

What Is the Molarity of a Potassium Triiodide Solution,KI3(aq),if 30

What Is the Molarity of a Potassium Triiodide Solution,KI₃(aq),if 30