Problem 2 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Given that \(\mathrm{E}_{\mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O}}^{\circ}=+1.23 \mathrm{~V} ;\) \(\mathrm{E}_{\mathrm{S}_{2} \mathrm{O}_{8}^{2-} / \mathrm{SO}_{4}^{2-}}=2.05 \mathrm{~V}\) \(\mathrm{E}_{\mathrm{Br}_{2} / \mathrm{Br}^{-}}^{\circ}=+1.09 \mathrm{~V}\) \(\mathrm{E}_{\mathrm{Au}^{3+} / \mathrm{Au}}^{\circ}=+1.4 \mathrm{~V}\) The strongest oxidising agent is : (a) \(\mathrm{Au}^{3+}\) (b) \(\mathrm{O}_{2}\) (c) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}\) (d) \(\mathrm{Br}_{2}\)

Step-by-Step Solution

Answer

The strongest oxidizing agent is S_2O_8^{2-} (option c).

Step 1: Understand Oxidizing Agent

An oxidizing agent is a substance that can accept electrons during a redox reaction. The ability of a substance to act as an oxidizing agent is indicated by its standard electrode potential ( E ) value. A higher positive value means a stronger oxidizing agent.

Step 2: Examine Given Electrode Potentials

List the provided electrode potential values to determine the strength of each oxidizing agent: - E_{O_2/H_2O}^{ rm{O}} = +1.23 V - E_{S_2O_8^{2-}/SO_4^{2-}} = 2.05 V - E_{Br_2/Br^{-}}^{ rm{O}} = +1.09 V - E_{Au^{3+}/Au}^{ rm{O}} = +1.4 V

Step 3: Compare Electrode Potentials

Compare the electrode potentials of the given species. The strongest oxidizing agent will have the highest positive electrode potential, as it indicates a greater tendency to gain electrons.

Step 4: Determine the Strongest Oxidizing Agent

Identify the species with the highest electrode potential: - E_{S_2O_8^{2-}/SO_4^{2-}} = 2.05 V is the highest among the given options.

Key Concepts

Oxidizing Agents

In the realm of electrochemistry, an oxidizing agent plays a crucial role in redox reactions. These substances have the ability to accept electrons from other substances, getting reduced in the process. When we talk about the strength of an oxidizing agent, we're referring to its potential to pull electrons away from another element or molecule.
A handy way to determine the strength of an oxidizing agent is by looking at its standard electrode potential. This value tells you how eagerly the agent wants to gain electrons. The higher the positive value, the stronger the oxidizing agent. Essentially, a high standard electrode potential means that the substance is more effective at stealing electrons during a redox reaction.
In everyday terms: think of oxidizing agents as electron "grabbers." The more they want the electrons, the higher their potential value, and the stronger they are.

Standard Electrode Potential

The standard electrode potential, often denoted as E°, is a measure of the energy involved in a redox reaction. It tells us how likely a substance is to be reduced (gain electrons) in a standard state. Textbooks often head toward this figure first when determining how reactions will play out.

• The standard electrode potential is measured in volts (V).
• A more positive E° value indicates a greater ability to act as an oxidizing agent.
• These values are normally determined under standardized conditions: 25°C, 1 atm pressure, and 1 molar concentration.

Standard electrode potentials help us understand the electrical aspects of chemical reactions. They are vital for calculating electromotive force (emf) in cells and figuring out which substances will preferentially react. So, when you see an E° value, it's a peek into how a chemical will behave when paired with another in a half-reaction.

Redox Reactions

Redox reactions are a fundamental concept in chemistry, involving the transfer of electrons between species. These reactions are characterized by two key processes: reduction and oxidation. In a redox reaction, one substance loses electrons (oxidized), while another gains those electrons (reduced).
Redox reactions are everywhere. They power our batteries, allow plants to photosynthesize, and even play a key role in our metabolism. Breaking it down further:

• **Oxidation** is the process where a substance loses electrons. The substance becomes more oxidized.
• **Reduction** involves the gaining of electrons. The reduced substance gains electrons and decreases in oxidation state.

The mnemonic "OIL RIG" is handy to remember: Oxidation Is Loss, Reduction Is Gain. Recognizing redox reactions and understanding their elements is significant in fields ranging from energy production to biochemistry. By following the electrons, you'll often see the bigger picture of what's happening in a chemical reaction.