Iodine/Thiosulfate Redox Titrations (OCR A-Level Chemistry A): Quizzes

$\text{S}_4\text{O}_6^{2-}$

1 mol $\text{ClO}^-$ ≡ 2 mol $\text{S}_2\text{O}_3^{2-}$

When solution becomes pale straw colour

Colourless

1 mol $\text{Cu}^{2+}$ ≡ 1 mol $\text{S}_2\text{O}_3^{2-}$

Copper content in brass alloys

To provide $\text{H}^+$ ions for the reaction

Deep blue-black

White copper(I) iodide (CuI)

It must oxidise $\text{I}^-$ to $\text{I}_2$