In iodometric titrations, sodium thiosulphate () reacts quantitatively with iodine () to form sodium — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

The balanced redox reaction is $I_2 + 2S_2O_3^{2-} \rightarrow 2I^- + S_4O_6^{2-}$. In this reaction, elemental iodine ($I_2$, oxidation state 0) is reduced to iodide ($I^-$, oxidation state -1). Each iodine atom gains 1 electron. Since there are 2 iodine atoms in $I_2$, a total of 2 moles of electrons are transferred per mole of $I_2$ consumed.