Why should sulfate ions (SO4^2-) not be capable of oxidizing bromide ions (Br-)?

The reason sulfate ions ((SO_4^{2-})) should not be capable of oxidizing bromide ions ((Br^-)) is primarily due to their electrode potentials. The standard electrode potential values determine the tendency of a species to gain electrons (be reduced) and thus affect its ability to act as an oxidizing agent. A higher electrode potential indicates a greater ability to oxidize other species.

In the case of sulfate ions, they have a lower standard electrode potential compared to bromide ions. This means that sulfate is less capable of gaining electrons than bromide, limiting its ability to act as an oxidizer. Since oxidation involves the loss of electrons from one species and the reduction of another, a species with a lower tendency to be reduced (like sulfate) will not effectively oxidize another species (like bromide), which has a higher reduction potential.

Therefore, the relationship between the electrode potentials of these ions is a key factor in determining their reactivity and their behavior as oxidizing or reducing agents.