In the manufacture of bromine from sea water, the mother liquor containing bromides is treated with: (a) Chlorine (b) Iodine (c) Sulphur dioxide (d) Carbon dioxide

In the context of bromine extraction from sea water, oxidation potentials play a crucial role in the selection of the appropriate oxidizing agent. Oxidation potential, also known as standard electrode potential, is a measure of a substance's tendency to gain electrons and thus be reduced. The higher the oxidation potential, the stronger the oxidizing agent.

When comparing oxidation potentials, if a potential is more positive, it indicates a greater tendency to acquire electrons and carry out the oxidation process. In the case of bromine extraction, we need to choose an oxidizing agent that has a higher oxidation potential than bromide ions to ensure an efficient and complete reaction.

• Chlorine, with an oxidation potential of +1.36 V for the Cl₂/Cl^- couple, is a strong oxidizing agent.
• Iodine and sulfur dioxide have lower oxidation potentials compared to chlorine, making them less suitable for the oxidation of bromide ions.
• Carbon dioxide is not typically considered a strong oxidizing agent, which makes it ineffective for this purpose.

Thus, chlorine, having one of the highest oxidation potentials among the given options, is the suitable choice for oxidizing bromide ions to bromine.

Chemical oxidation is the process by which a chemical substance loses electrons and increases its oxidation state. This reaction typically involves the transfer of electrons from the substance being oxidized (in this context, bromide ions) to the oxidizing agent (chlorine).

The oxidation of bromide ions (\text{Br}^{-}) can be represented by the half-equation: \[\text{2Br}^{-} (aq) \rightarrow \text{Br}_{2} (l) + 2e^{-}\].

In this equation, bromide ions lose electrons (get oxidized) and form bromine molecules. The efficiency of this chemical oxidation depends on the oxidizing agent's ability to accept electrons. Chlorine, being a strong oxidizing agent, readily accepts electrons from the bromide ions, leading to the formation of bromine and chloride ions.

Due to this electron transfer, chlorination (using chlorine gas) is commonly employed in industrial bromine extraction processes. This reaction occurs in an acidic environment within the brine solution, which is typically achieved by controlled pH levels in commercial operations.

Bromide ions (\text{Br}^{-}) are the starting material for the extraction of bromine from sea water. These ions are abundant in sea water as various salts, primarily in the form of sodium bromide (NaBr).

In their ionic form, bromide ions are colorless, water-soluble, and bear a single negative charge. During the extraction process, these ions are oxidized to form diatomic bromine (\text{Br}_{2}), which is the element in its pure form. Here's the full reaction when chlorine is used as the oxidizing agent: \[\text{Cl}_2 (g) + 2\text{Br}^{-} (aq) \rightarrow 2\text{Cl}^{-} (aq) + \text{Br}_2 (l)\].

The reaction indicates that the bromide ions are transforming into molecular bromine while chloride ions remain in solution. This transformation is fundamental to the production of bromine and showcases the importance of bromide ions in the overall process. By subsequently collecting the evaporated bromine, we have successfully converted the dissolved salts from sea water into valuable bromine.