Chapter 19, Problem 84A

Interpretation Introduction

Interpretation:

The given reaction is to be balanced using the half reaction method.

Concept introduction:

In the half reaction method, the oxidation and reduction half reactions are separately balanced, then added to for the complete equation.

Answer to Problem 84A

The balanced equation for the given reaction is:

${\text{2S}}_2{O}_3{}^{2-}+I_2\to S_4{O}_6{}^{2-}+2I^{-}$

Explanation of Solution

The balanced chemical equation can be obtained by adding oxidation and reduction half reactions.

$\begin{array}{l}\text{The oxidation half reaction:}\\ {\text{2S}}_2{O}_3{}^{2-}\to S_4{O}_6{}^{2-}+2e^{-}\\ \text{The reduction half reaction:}\\ I_2+2e^{-}\to 2I^{-}\\ \text{Adding both equations, :}\\ {\text{2S}}_2{O}_3{}^{2-}+I_2\to S_4{O}_6{}^{2-}+2I^{-}\\ \text{which is the balanced equation}\text{.}\end{array}$