# Determining the half-potential using Latimer diagram

$$\ce{\overset{+7}{Br}O4- ->[\pu{+1.82 V}] \overset{+5}{Br}O3- ->[\pu{+1.49 V}] H\overset{+1}{Br}O ->[\pu{+1.59 V}] \overset{0}{Br}_2 ->[\pu{+1.07 V}] \overset{-1}{Br}^-}$$

I'm supposed to identify the ones that are unstable with respect to disproportionation and determine the half-potential for the reduction of the bromate ion to bromine. So far I have figured out that $$\ce{HBrO}$$ is unstable, but I'm not sure how to determine the half-potential given the diagram.

• If I understand you correctly, to determine the half-potential for the reduction, you should use the idea of the standard Gibbs free energy change ($\Delta$ G = - nFE), taking into account the number of electrons transferred in each step of the reduction, n. After calculating the $\Delta$ G for the overall reduction process, by summing the individual $\Delta$ Gs for each step, you can then calculate the half-potential using the overall number of electrons transferred, n. – Tan Yong Boon Sep 26 '19 at 0:20