Question

The standard reduction clectrode potential values of the clements \(\Lambda, B\) and \(C\) are \(+0.68,-2.5\) and \(-0.5 \mathrm{~V}\), respectively. The order of their reducing power is (1) \(\mathrm{A}>\mathrm{B}>\mathrm{C}(2) \mathrm{A}>\mathrm{C}>\mathrm{B}\) (3) \(C>B>A(4) B>C>A\)

Short answer

Option (4) B > C > A.

Step-by-step solution

- Understand Electrode Potential

The electrode potential measures the tendency of a substance to gain electrons and undergo reduction. A higher (more positive) reduction potential indicates a greater tendency to be reduced.

- Analyze Given Values

The given standard reduction electrode potentials for elements are:- \(A: +0.68 V\)- \(B: -2.5 V\)- \(C: -0.5 V\)Values closer to positive indicate elements more likely to gain electrons (reduction), while more negative values indicate better reducing agents.

- Determine Reducing Power

An element that is a good reducing agent (stronger reducing power) has a lower (more negative) standard electrode potential, as it more readily loses electrons (is oxidized).

- Rank Elements by Reducing Power

Rank from the most negative potential to the least negative:- \(B: -2.5 V\) is the most negative (strongest reducing agent)- \(C: -0.5 V\) is less negative- \(A: +0.68 V\) is the least negative (weakest reducing agent)Thus, the order of reducing power is \(B > C > A\).

- Select Correct Option

From the provided options, the correct order is (4) \(B > C > A\).

Key concepts

Reducing Power

Reducing power refers to the ability of a substance to donate electrons in a chemical reaction. Substances with higher reducing power are better at losing electrons and are therefore stronger reducing agents. Elements with more negative standard reduction electrode potentials have greater reducing power.
This is because they readily undergo oxidation, losing electrons easily.
In the given exercise, element B with a standard reduction potential of -2.5 V has the highest reducing power, followed by element C at -0.5 V, and lastly, element A at +0.68 V which has the lowest reducing power.
To summarize:

• Reducing power is the ability of an element to lose electrons.
• More negative standard electrode potentials indicate stronger reducing agents.
• In this case, B has the highest reducing power followed by C and then A.

Oxidation-Reduction Potential

Oxidation-Reduction potential (also known as redox potential) is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. It is expressed in volts (V) and can be either positive or negative.
A positive redox potential means that a species is more likely to accept electrons (undergo reduction), while a negative redox potential indicates that a species is more likely to lose electrons (undergo oxidation).
For example:

• Element A with a redox potential of +0.68 V is likely to be reduced.
• Element B with a redox potential of -2.5 V is likely to be oxidized (and thus is a good reducing agent).
• Element C with a redox potential of -0.5 V falls in between.

Understanding redox potential is crucial in predicting how different substances will react, particularly in redox reactions where one species is oxidized and another is reduced.

Electrochemical Series

The Electrochemical Series is a list of elements and their standard reduction electrode potentials arranged in order of decreasing oxidizing power (increasing reducing power). This series helps in determining which elements are better at undergoing reduction (gaining electrons) or oxidation (losing electrons).
Elements higher in the series have more positive electrode potentials and are stronger oxidizing agents.
Conversely, elements lower in the series have more negative electrode potentials and are stronger reducing agents.
For instance:

• Element A (+0.68 V) will be higher in the electrochemical series, meaning it is a better oxidizing agent.
• Element B (-2.5 V) will be lower, meaning it is a stronger reducing agent.
• Element C (-0.5 V) will fall somewhere in between.

Knowing the electrochemical series allows us to predict and understand the outcomes of various electrochemical reactions, making it a fundamental tool in chemistry.