Question 21.8: Calculate Ered and Eox at 25°C for the ClO3- ion in neutral ...

Calculate E_{red} and E_{ox} at 25°C for the ClO_{3}^{-} ion in neutral solution, at pH 7.00, assuming all other species are at standard concentration (E°_{red} = +1.442 V; E°_{ox} = -1.226 V). Will the ClO_{3}^{-} ion disproportionate at pH 7.00?

STRATEGY

1. Write a half-equation for the reduction of ClO_{3}^{-} .

2. Calculate E_{red} by substituting into the Nernst equation for 25°C.

E_{red} = E°_{red}  –  \frac{0.0257}{n}lnQ

3. Write a half-equation for the oxidation of ClO_{3}^{-} .

4. Calculate E_{ox} by substituting into the Nernst equation for 25°C.

E_{ox} = E°_{ox}  –  \frac{0.0257}{n}lnQ

5. Find E
E = E_{red} + E_{ox}

If E > 0, ClO_{3}^{-}  will disproportionate.