Problem 45 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The standard reduction potential values of three metallic cations, \(X, Y\) and \(Z\) are \(0.52,-3.03\) and \(-1.18 \mathrm{~V}\) respectively. The order of reducing power of the corresponding metals is [1998 - 2 Marks] (a) \(Y>Z>X\) (b) \(X>Y>Z\) (c) \(Z>Y>X\) (d) \(Z>X>Y\)

Step-by-Step Solution

Answer

The order is (a) \(Y > Z > X\).

Step 1: Understanding Reduction Potentials

Reduction potential indicates the tendency of a substance to gain electrons (get reduced). The higher (more positive) the reduction potential, the greater the tendency to gain electrons (and thus the weaker the reducing power). Conversely, a lower (more negative) reduction potential indicates a stronger reducing agent.

Step 2: Analyze Given Potentials

We are given the standard reduction potentials for cations: \(X = 0.52 \, \text{V}\), \(Y = -3.03 \, \text{V}\), and \(Z = -1.18 \, \text{V}\). We need to determine the reducing power, which is stronger for more negative potentials.

Step 3: Compare Reducing Powers

Compare based on their potentials. A more negative potential means stronger reducing power:- \(Y = -3.03 \, \text{V}\) is most negative.- \(Z = -1.18 \, \text{V}\) is less negative than \(Y\).- \(X = 0.52 \, \text{V}\) is least negative (or positive).Thus, the order of reducing power is \(Y > Z > X\).

Step 4: Match Order with Options

The correct order of reducing power is \(Y > Z > X\). Checking this sequence against the given options reveals that option (a) matches this order.

Key Concepts

Reduction Potential

Reduction potential is a crucial concept in electrochemistry. It shows how easily a substance can accept electrons, meaning it's being reduced. The reduction potential value is generally given in volts (V). If this value is higher and positive, that means the substance has a strong willingness to gain electrons and be reduced.
However, a more negative reduction potential indicates that the substance prefers to lose electrons rather than gain them. This implies a weaker tendency to undergo reduction but a stronger capability as a reducing agent.
In brief:

• High positive values = strong oxidizing agent (easily gains electrons and reduced).
• Low negative values = strong reducing agent (likely to lose electrons).

The relationship between reduction potential and reducing power is an inverse one. Knowing this helps in predicting chemical reactions and identifying stronger reducing agents.

Reducing Power

Reducing power refers to the ability of a substance to donate electrons. Substances with more negative reduction potentials have a high reducing power because they can easily give away electrons. This makes them excellent reducing agents in chemical reactions.
In a sequence:

• Higher negative values = greater reducing power.
• Lower negative values = lesser reducing power.

Considering the given metallic cations, the reduction potentials are seen as follows: Y has -3.03 V, Z has -1.18 V, and X has 0.52 V. Thus, Y, with the most negative potential, is the strongest reducing agent, followed by Z, and then X. Therefore, understanding reducing power is essential for predicting how substances will interact in a chemical reaction.

Metallic Cations

Metallic cations are positively charged ions formed when metals lose electrons. In electrochemistry, their properties are often linked to their reduction potentials, which help predict how these cations might behave in a reaction.
For instance:

• Cations with high reduction potentials are less likely to give up electrons; they prefer to stay reduced.
• Those with low or negative reduction potentials tend to donate electrons, acting as reducing agents.

In practical terms, this explains how metals react and how they might be used in various industrial processes. Metals like those in the original exercise, with different reduction potentials, illustrate this concept by ordering their reducing power based on their potential values. This helps in selecting appropriate metals for specific industrial applications and reactions.