Problem 56 - A Complete Resource Book in Chemistry for JEE Main

Question

A standard hydrogen electrode has zero electrode potential because (a) hydrogen is easiest to oxidize (b) its electrode potential is assumed to be zero (c) hydrogen atom has only one electron (d) hydrogen is the lightest element

Step-by-Step Solution

Answer

(b) its electrode potential is assumed to be zero.

Step 1: Understanding Standard Hydrogen Electrode

The standard hydrogen electrode (SHE) is used as a reference electrode with an assigned electrode potential set to zero. It helps in measuring the electrode potential of other electrodes.

Step 2: Reason for Zero Electrode Potential

The electrode potential of the standard hydrogen electrode is not determined by physical properties but rather as a convention. It is arbitrarily assumed to be zero to provide a reference for comparing other electrode potentials.

Step 3: Analyze Options

Evaluate each provided option: (a) is incorrect because ease of oxidation doesn't justify the zero potential setting. (b) is correct as the zero potential is an assumption. (c) and (d) do not relate to the assignment of the SHE potential.

Step 4: Conclusion

The correct reason that the standard hydrogen electrode has zero electrode potential is because its electrode potential is assumed to be zero by convention.

Key Concepts

Electrode Potential

Electrode potential is a measure of the tendency of a chemical species to acquire electrons and be reduced.
When we talk about electrode potential, we're essentially discussing how readily an electrode will gain or lose electrons in a redox reaction.
This property is crucial for understanding the behavior of electrochemical cells.

• Electrode potential can either be a reduction potential or an oxidation potential.
• A positive electrode potential indicates a good oxidizing agent, while a negative indicates a good reducing agent.

The electrode potential is determined under standard conditions, typically using the standard hydrogen electrode as a baseline.
It is the difference in potential between the electrode of interest and the hydrogen electrode, allowing scientists to compare how different electrodes behave in various chemical reactions.

Reference Electrode

The concept of a reference electrode is integral to electrochemistry and helps in measuring the electrode potentials accurately.
A reference electrode provides a stable and known potential against which the potential of another half-cell can be measured.

• The standard hydrogen electrode (SHE) is the most common reference electrode.
• It is assigned an arbitrary zero potential under standard conditions to serve as a baseline.
• Using a reference electrode helps in calculating the cell potential, which is essential in determining the spontaneity and direction of redox reactions.

Reference electrodes are vital in maintaining the consistency and comparability of electrochemical measurements.
Without such a baseline, it would be challenging to accurately determine the behavior of different chemical reactions.

Oxidation-Reduction Reactions

Oxidation-reduction, or redox reactions, are processes where electrons are transferred between chemical species.
These reactions play a pivotal role in energy production and various industrial processes.

• Oxidation refers to the loss of electrons, while reduction involves the gain of electrons.
• Redox reactions always occur in pairs, with one substance being oxidized and another being reduced.
• The concept of oxidation numbers helps track electron transfer throughout the reaction.

Understanding redox reactions is critical for grasping electrochemical principles.
They are the foundational mechanisms inside batteries, electroplating, and in biological processes such as cellular respiration.
The controlled transfer of electrons in these reactions is what provides the capability to achieve chemical conversions and energy transformations.