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 mol L^-1 thiosulfate solution,K₂S₂O₃(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 equation shows that 2 moles of thiosulfate react with 1 mole of triiodide. Calculate moles of thiosulfate: 0.200 mol/L * 0.025 L = 0.005 mol. Therefore, moles of triiodide = 0.005 mol / 2 = 0.0025 mol. Molarity of KI3 = 0.0025 mol / 0.030 L = 0.0833 mol/L.

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