Problem 156 - 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 \(0.50 \mathrm{~V},-3.03 \mathrm{~V}\) and \(-1.2 \mathrm{~V}\) respectively. The order of reducing power of the corresponding metals is (a) \(\mathrm{X}>\mathrm{Y}>\mathrm{Z}\) (b) \(Z>Y>X\) (c) \(\mathrm{Y}>\mathrm{Z}>\mathrm{X}\) (d) \(\mathrm{X}>\mathrm{Z}>\mathrm{Y}\)

Step-by-Step Solution

Answer

The correct order of reducing power is (c) \(\mathrm{Y} > \mathrm{Z} > \mathrm{X}\).

Step 1: Understand Reduction Potential

Reduction potential measures the tendency of a chemical species to acquire electrons and be reduced. A higher reduction potential indicates a greater tendency to be reduced and, conversely, a lower reduction potential means a greater tendency to oxidize.

Step 2: List the Reduction Potentials

The reduction potentials given are: X = 0.50 V, Y = -3.03 V, Z = -1.2 V. X has the highest reduction potential, followed by Z, and Y has the lowest.

Step 3: Determine Reducing Power

The reducing agent is the species that donates electrons, so the metal with the lowest reduction potential will be the strongest reducing agent. This means the order of reducing power is the opposite of their reduction potentials.

Step 4: Arrange Metals by Reducing Power

Since metals with lower reduction potentials have higher reducing power, their order is: Y > Z > X.

Step 5: Match with Given Options

The order Y > Z > X corresponds to option (c) in the given choices.

Key Concepts

Reducing Power

Reducing power refers to the ability of a substance to donate electrons during a chemical reaction. This ability is what defines a reducing agent. The strength of a reducing agent is determined by its tendency to release electrons and become oxidized in the process.
Reducing agents are essential in various chemical processes, including metal extraction and biological reactions. Some points to consider include:

• A strong reducing agent readily donates electrons to another species.
• The strength of reducing power is inversely related to the reduction potential of a substance.
• A species with a lower (more negative) reduction potential tends to have a higher reducing power.

In the context of electrochemistry, understanding reducing power helps us evaluate how different metals will behave in oxidation-reduction reactions.

Oxidation-Reduction Reactions

Oxidation-reduction reactions, often called redox reactions, are chemical processes where electrons are transferred between two species. These reactions are fundamental to understanding how different chemical substances interact.
A redox reaction consists of:

• Oxidation: This involves the loss of electrons by a molecule, atom, or ion.
• Reduction: This involves the gain of electrons by another molecule, atom, or ion.

These reactions are characterized by changes in oxidation states of the participating species. The substance that donates electrons is called the reducing agent, while the one that accepts electrons is the oxidizing agent. To determine which substance will act as a reducing agent in a given reaction, comparing their reduction potentials is key:

• The substance with a lower reduction potential generally serves as the better reducing agent.
• Electrons flow from the reducing agent to the oxidizing agent, driving the redox reaction forward.

Redox reactions play an essential role in processes such as energy production and corrosion.

Electrochemistry

Electrochemistry is the branch of chemistry that explores the relationship between electricity and chemical reactions. It is primarily concerned with the study of reactions where electrons are transferred between species, causing oxidation and reduction.
In electrochemical reactions, the flow of electrons can be harnessed to produce electrical energy or, conversely, to drive chemical changes through an input of electrical energy. Key components of electrochemical systems include:

• Electrodes: These are conductive materials where oxidation and reduction occur.
• Electrolytes: These are solutions that allow the movement of ions to balance the flow of electrons.

Standard reduction potentials are crucial in determining the direction and feasibility of electron flow in electrochemical cells. They help us predict which reactions will occur and under what conditions. Electrochemical applications are widespread: they power batteries, enable electroplating, and facilitate industrial processes such as electrolysis. Understanding electrochemistry fundamentally aids in grasping both natural biological processes and advanced technological applications.