Redox Titration 2: Iodine and Sodium Thiosulfate (Leaving Cert Chemistry): Flashcards

Reducing agent

$\text{Na}_2\text{S}_2\text{O}_3 \cdot 5\text{H}_2\text{O}$

Five water molecules

$\text{S}_2\text{O}_3^{2-}$

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

Oxidising agent

1:2

Efflorescent - loses water, making accurate weighing impossible

When solution becomes pale yellow

Blue-black

Blue-black colour disappears

Sulfur has replaced oxygen

$\text{I}_2 + \text{I}^- \rightarrow \text{I}_3^-$

To prevent decomposition

Tetrathionate ion ($\text{S}_4\text{O}_6^{2-}$)