Problem 22 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

A gas \(X\) at 1 atm is bubbled through a solution containing a mixture of \(1 \mathrm{M} Y^{-}\)and \(1 \mathrm{M} Z^{-}\)at \(25^{\circ} \mathrm{C}\). If the reduction potential of \(Z>Y>X\) then, [1999 - 2 Marks] (a) \(Y\) will oxidize \(X\) and \(\operatorname{not} Z\) (b) \(Y\) will oxidize \(Z\) and \(\operatorname{not} X\) (c) \(Y\) will oxidize both \(X\) and \(Z\) (d) \(Y\) will reduce both \(X\) and \(Z\)

Step-by-Step Solution

Answer

\(Y\) will oxidize \(X\) but not \(Z\) (Option a).

Step 1: Understand Reduction Potentials

Reduction potential represents a substance's tendency to gain electrons. A higher reduction potential means a stronger oxidizing agent, as it suggests a greater ability to be reduced.

Step 2: Compare Reduction Potentials

Given the reduction potentials: \(Z > Y > X\), \(Z\) has the highest potential, followed by \(Y\), and then \(X\). Therefore, \(Z\) is the strongest oxidizing agent.

Step 3: Identify Possible Reactions

Since reducing agents donate electrons, \(Y\) and \(Z\) are candidates for reducing \(X\). However, the task specifies identifying which elements \(Y\) will oxidize.

Step 4: Deduce Role of \(Y\)

\(Y\), being a weaker oxidizing agent than \(Z\) but stronger than \(X\), cannot oxidize \(Z\) (as \(Z\) has a higher reduction potential) but can oxidize \(X\), since \(X\) has a lower reduction potential.

Key Concepts

Reduction Potential

Reduction potential is a measure of a substance's ability to gain electrons in a chemical reaction. It is often expressed in volts and is measured relative to a standard. When you hear the term reduction potential, think of it as a way to gauge how "hungry" a molecule is for electrons. The more it craves electrons, the higher its reduction potential.

Higher reduction potential indicates a stronger oxidizing agent. Why? Because oxidizing agents are substances that accept electrons. By accepting electrons, they get reduced. So, a molecule with a high reduction potential is very effective at taking electrons from others. This concept is essential when figuring out which substances can drive redox reactions.

In the exercise context, if we list substances by their reduction potentials, with the highest at the top, we can infer which substances are likely to be reduced in reactions. Here, the order is given as \( Z > Y > X \). This means \( Z \) is more capable of accepting electrons than \( Y \), and \( Y \) is more capable than \( X \).

Oxidizing Agent

An oxidizing agent is a substance that gains electrons in a chemical reaction. As it takes in electrons, it undergoes reduction. The agent essentially brings about oxidation in another substance by extracting its electrons.

Consider an oxidizing agent as the electron "collector" in redox reactions. It has a high reduction potential, making it very "interested" in collecting electrons. The stronger the oxidizing agent, the higher its reduction potential will be.

In the specific example from the exercise, since \( Z \) has the highest reduction potential, it acts as the most potent oxidizing agent. However, the question is focused on \( Y \). Even though \( Y \) is not the strongest, it has a higher reduction potential than \( X \), making \( Y \) capable of oxidizing \( X \). This means that \( Y \) can take electrons from \( X \), causing \( X \) to lose electrons and become oxidized.

Redox Reaction

Redox, short for reduction-oxidation, involves the transfer of electrons between two substances. One substance loses electrons and becomes oxidized, while the other gains those electrons and is reduced. Imagine redox reactions as a sort of electron "dance" where electrons move from one partner to another.

A key part of understanding redox reactions is recognizing the roles of the substances involved. The oxidizing agent gets reduced, as it gains electrons, and the reducing agent gets oxidized, as it loses electrons.

In our exercise, the gas \( X \) could potentially be part of a redox reaction with \( Y \) or \( Z \). Despite \( Z \) being the strongest oxidizing agent, the focus is on \( Y \). Because the reduction potential of \( Y \) is greater than \( X \), \( Y \) can accept electrons from \( X \). This implies that \( Y \) induces \( X \) to oxidize, completing the redox reaction. In such reactions, tracking which species are gaining or losing electrons helps you predict the outcome and identify the roles of each reactant.