Problem 82 - A Complete Resource Book in Chemistry for JEE Main

Question

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

Step-by-Step Solution

Answer

Chlorine (a) is used to extract bromine from seawater.

Step 1: Identify the Reaction Process

Understand the process of extracting bromine from seawater. Bromine is extracted by treating the bromide ions in seawater with a substance that will oxidize the bromides to free bromine.

Step 2: Analyze the Options

Review the given options to determine which can act as an oxidizing agent to convert bromide (Br⁻) to bromine (Br₂): (a) chlorine, (b) iodine, (c) sulphur dioxide, (d) carbon dioxide. An oxidizing agent should have a higher electronegativity than bromide.

Step 3: Determine the Suitable Oxidizing Agent

Recognize that chlorine (a) can facilitate the reaction by oxidizing bromide ions because it is a stronger oxidizing agent than bromine. The reaction can be represented as: \[ Cl_2 + 2Br^- \rightarrow 2Cl^- + Br_2 \]

Step 4: Conclude the Correct Answer

From the analysis, chlorine effectively oxidizes bromide ions to free bromine in the manufacturing process.

Key Concepts

Oxidizing Agents: The Heart of Bromine Extraction

In the context of bromine extraction from seawater, an oxidizing agent plays a crucial role. An oxidizing agent is a substance that gains electrons in a chemical reaction, causing another substance to lose electrons. This process is called oxidation. During the extraction of bromine, bromide ions (Br^-) need to be converted into elemental bromine (Br_2). This is where the oxidizing agent comes into play.

The ideal oxidizing agent for this process must have a higher affinity for electrons compared to bromine. Among the options, chlorine (Cl_2) stands out due to its high electronegativity and its ability to accept electrons readily. This makes it perfect for oxidizing bromide ions. The chemical reaction can be represented as: \[Cl_2 + 2Br^- \rightarrow 2Cl^- + Br_2\]

This equation demonstrates chlorine taking electrons from bromide ions, resulting in chloride ions (Cl^-) and liberated bromine. This effective use of an oxidizing agent is a cornerstone in the industrial production of bromine from seawater.

Sea Water Chemistry: The Foundation for Bromine

Seawater is not just salt and water; it's a complex solution containing diverse ions and minerals. One of these crucial ions is the bromide ion ( Br^- ). Despite being less abundant than chloride ions ( Cl^- ), bromide ions are present in significant quantities to allow commercial extraction of bromine from the sea.

The chemistry of seawater provides a unique environment where these reactions can occur efficiently. It's a powerful chemical reservoir, supporting a range of redox reactions due to the variety of ions present. Bromine extraction is just one example of how we tap into seawater's rich chemistry. By understanding the dynamics of these ions, we can effectively manipulate them to extract valuable elements like bromine.

• High availability of bromide ions in seawater
• Presence of other reactive substances like chloride ions
• Unique chemical conditions that support redox reactions

This knowledge is essential for industries relying on the precise recovery of chemicals from natural resources like seawater.

Bromide Ions: The Building Blocks of Bromine

Bromide ions ( Br^- ) are the starting point for bromine extraction. These ions are abundant in seawater, making the ocean a vital resource for bromine production. Even though they form a small percentage of the overall ionic content, their high concentration across vast sea volumes makes extraction feasible.

Bromide ions are negatively charged, having gained an extra electron compared to the elemental bromine. In the extraction process, these bromide ions undergo oxidation, losing this extra electron. This loss leads to the formation of elemental bromine ( Br_2 ), a reddish-brown liquid highly used in various industries.

Understanding the properties and behavior of bromide ions helps in efficiently executing their conversion into bromine. This knowledge is crucial for controlling the quality and yield of bromine extracted, influencing products we encounter daily:

• Flame retardants
• Drugs
• Photographic chemicals

Thus, the chemistry of bromide ions forms the groundwork for not just extraction but also innovation in the chemical industry.