Problem 53 - A Complete Resource Book in Chemistry for JEE Main

Question

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

Step-by-Step Solution

Answer

(a) \( \mathrm{Y} > \mathrm{Z} > \mathrm{X} \)

Step 1: Understand Reducing Power

The reducing power of a metal is inversely related to its standard reduction potential. This means that the lower the standard reduction potential of a metal, the higher its ability to act as a reducing agent.

Step 2: List Given Standard Reduction Potentials

We are given the standard reduction potentials of metals X, Y, and Z as follows: \[ E^0(X) = 0.52 \] \[ E^0(Y) = -3.03 \] \[ E^0(Z) = -1.18 \].

Key Concepts

Standard Reduction Potential

In electrochemistry, the standard reduction potential is crucial in determining a metal's ability to act as a reducing agent. It is the measure of the tendency of a chemical species to gain electrons and be reduced. Every metal has a unique standard reduction potential, which is normally expressed in volts (V).
Understanding how standard reduction potential works can help predict chemical reactions, especially those involving electron transfer. Metals with lower standard reduction potentials are typically stronger reducing agents, as they are more willing to donate electrons to other substances. This can be counterintuitive at first, but it emphasizes the concept that a lower potential means a higher reducing strength.

• High standard reduction potential: Low reducing power (less likely to donate electrons)
• Low standard reduction potential: High reducing power (more likely to donate electrons)

By comparing the given potentials, it's easy to arrange metals according to their reducing ability. For example, in our exercise, Metal Y has the lowest potential of e.g., -3.03, indicating it has the highest reducing power.

Electrochemistry

Electrochemistry deals with the interaction between electrical energy and chemical reactions. It's a branch of chemistry where the primary focus is on how electricity can cause chemical changes or how chemical reactions can produce electrical energy. This field underpins many processes we rely on daily, such as battery function and electroplating.
In the context of standard reduction potentials, electrochemistry helps explain the energy changes during electron transfer reactions. When considering a cell, the metal that has the lower standard reduction potential will oxidize, releasing electrons that can be used to do work in a circuit.

• Oxidation: Loss of electrons, occurs at the anode
• Reduction: Gain of electrons, occurs at the cathode
• The cell potential combines the oxidation and reduction potentials

Electrochemical cells, such as galvanic or voltaic cells, convert chemical energy into electrical energy, which is described by these reduction potentials. Understanding these concepts is vital for predicting and harnessing chemical reactions for energy production.

Metallic Cations

Metallic cations are positively charged ions formed when metals lose electrons. This process is crucial in redox reactions, where one species loses electrons (is oxidized) while another gains electrons (is reduced). The cations' properties and behaviors are dictated by their electronic configuration and standard reduction potential.
When metals transform into cations, they play a significant role in electrochemical reactions. As seen in the exercise, we compare the standard reduction potentials of the cations X, Y, and Z to predict the order of their reducing power.
The metallic cations act as oxidizing agents in these reactions, the higher their potential to attract electrons (lower standard reduction potential), the better they act as reducing agents themselves. Here's a quick refresher on characteristics:

• Cations are involved in the flow of electrons in electrochemical cells
• Lower standard reduction potential indicates higher readiness to be oxidized, providing electrons
• Watch for the balance between their electron loss and gain in reactions

By understanding the characteristics of metallic cations, we can better predict their behavior in different chemical environments, aiding in everything from energy storage technologies to metallurgy processes.