Problem 111 - A Complete Resource Book in Chemistry for JEE Main

Question

A gas at \(1 \mathrm{~atm}\) is bubbled through a solution containing a mixture of \(1 \mathrm{M} \mathrm{Y}^{-}\)and \(1 \mathrm{M} \mathrm{Z}^{-}\)at \(25^{\circ} \mathrm{C}\). If the reduction potential of \(Z>Y>X\), then (a) \(\mathrm{Y}\) will oxidize \(\mathrm{X}\) and not \(\mathrm{Z}\) (b) \(\mathrm{Y}\) will oxidize \(\mathrm{Z}\) and \(\mathrm{not} \mathrm{X}\)

Step-by-Step Solution

Answer

(a)\(Y\) will oxidize \(X\) and not \(Z\).

Step 1: Understand Reduction Potentials

Reduction potential is a measure of the tendency of a species to gain electrons and be reduced. A species with a higher reduction potential is more likely to gain electrons (be reduced) than one with a lower reduction potential. Thus, the sequence given, \(Z>Y>X\), means \(Z\) is more easily reduced than \(Y\), and \(Y\) is more easily reduced than \(X\).

Step 2: Determine the Oxidizing and Reducing Agents

A species with a higher reduction potential acts as an oxidizing agent because it can gain electrons. Conversely, a species with a lower reduction potential acts as a reducing agent because it can donate electrons. Therefore, \(Z\) is the strongest oxidizing agent and \(X\) is the strongest reducing agent in this context.

Step 3: Analyze the Electron Transfer Possibilities

Since \(Y\) is less easily reduced than \(Z\) (lower reduction potential) and more easily reduced than \(X\) (higher reduction potential), \(Y\) can potentially oxidize \(X\) (because \(X\) can donate electrons to \(Y\)), but \(Y\) cannot oxidize \(Z\) (since \(Z\) would need to donate electrons, which it does not tend to do because it has a higher reduction potential).

Step 4: Conclusion Based on Analysis

Given that \(Y\) cannot oxidize \(Z\) because it has a lower reduction potential than \(Z\), the possible scenario is for \(Y\) to oxidize \(X\) (because \(Y\) has a higher reduction potential than \(X\)). Hence, \(Y\) will oxidize \(X\) and not \(Z\).

Key Concepts

Reduction Potential

Reduction potential is a central concept in electrochemistry, representing the tendency of a chemical species to gain electrons and undergo reduction. This concept allows us to predict which substances in a solution are more likely to accept electrons and which ones are more likely to donate them. The higher the reduction potential, the more readily a species will gain electrons and be reduced. In other words, a high reduction potential indicates a strong affinity for electrons.

In the context of the original exercise provided, if the reduction potentials of three substances are arranged such that \(Z > Y > X\), then \(Z\) would be the species with the highest tendency to be reduced, followed by \(Y\) and then \(X\). This sequence informs us about the relative strengths of the substances in terms of their electron-accepting capabilities. Understanding this hierarchy is crucial as it predicts the direction of electron flow in electrochemical reactions.

Oxidizing Agents

An oxidizing agent is a substance that has the ability to oxidize other substances, meaning it facilitates the loss of electrons from these substances. Oxidizing agents are often found with high reduction potentials, as they are keen to gain electrons themselves.

In our exercise, \(Z\) is identified as the strongest oxidizing agent because it has the highest reduction potential, meaning it is the most inclined to accept electrons. When an oxidizing agent undergoes reduction (gains electrons), it causes another substance to lose electrons, thereby oxidizing it. As a rule of thumb in electrochemistry, remember:

• The stronger the oxidizing agent, the higher its reduction potential.
• Reduction happens to the oxidizing agent, causing oxidation in another.

When approaching electrochemical problems, identifying the strongest oxidizing agent helps determine which reactions are feasible based on electron transfer tendencies.

Reducing Agents

Reducing agents, in contrast to oxidizing agents, are substances that lead to the reduction of others by donating electrons. Because they are donors, reducing agents are characterized by low reduction potentials. Such agents readily lose electrons, which are then gained by other chemical species.

In the exercise scenario, \(X\) is depicted as the strongest reducing agent due to its lowest reduction potential among the three. This means \(X\) is more likely than \(Y\) or \(Z\) to donate electrons. Key points to note about reducing agents:

• The stronger the reducing agent, the lower its reduction potential.
• They are oxidized themselves during the reaction, providing electrons to another substance.

Recognizing the strongest reducing agent in a sequence allows us to foresee which substances might be oxidized due to electron donation. This insight is critical in predicting the outcomes of redox reactions in a given chemical environment.