Question

Bromine is sometimes used in place of chlorine as a disinfectant in swimming pools. If the effectiveness of a chemical as a disinfectant depends solely on its strength as an oxidizing agent, do you expect bromine to be better or worse than chlorine as a disinfectant, at a given concentration?

Short answer

Chlorine is a stronger reducing agent than bromine and a weaker oxidising agent.

Step-by-step solution

Definition of oxidizing and reducing agent.

Oxidizing agent: In a chemical reaction, oxidising agents are molecules that gain electrons.

Reducing agent: A material that can lose electrons is referred to as a reducing agent.

Explanation of solution.

Let us start by looking up the usual reduction potentials for:

For bromine:${\text{E}}^{\text{o}}\left({\text{Br}}_{\text{2}}\mid {\text{Br}}^{\text{-}}\right)\text{=1.065V}$

For chlorine:${\text{E}}^{\text{o}}\left({\text{Cl}}_{\text{2}}\mid {\text{Cl}}^{\text{-}}\right)\text{=1.3583V}$

The stronger the reducing agent, the more positive$\left(\text{>}\right)$the standard reduction potential is.

When we compare the two compounds, we discover:

${\text{E}}^{\text{o}}\left(\text{Cl\_2}\mid {\text{Cl}}^{\text{-}}\right){\text{>E}}^{\text{o}}\left(\text{Br\_2}\mid {\text{Br}}^{\text{-}}\right)$

From above formula we conclude that chlorine is a greater reducing agent and a weaker oxidising agent than bromine.