Question

The calomel electrode is a (1) Standard hydrogen electrode (2) Reference electrode (3) Platinum electrode (4) Mercury electrode

Short answer

(2) Reference electrode

Step-by-step solution

Understand the Calomel Electrode

A calomel electrode is an electrode based on the reaction between mercury and mercury chloride (calomel) in a saturated potassium chloride solution.

Recognize the Types of Electrodes

Identify the different types of electrodes given in the question. They are: Standard hydrogen electrode, Reference electrode, Platinum electrode, and Mercury electrode.

Identify the Function

A calomel electrode functions as a reference electrode because it maintains a stable electrode potential, which is essential for measuring the potential of other electrodes.

Choose the Correct Option

Based on the understanding that a calomel electrode is a type of reference electrode, identify the correct option from the given choices.

Key concepts

reference electrode

A reference electrode is a crucial component in electrochemical cells. It provides a stable and known potential against which other electrode potentials can be measured. This stability is vital for obtaining accurate and reproducible results in electrochemical experiments.
Reference electrodes act as a benchmark for comparing the behavior of working electrodes. They do not participate in the chemical reactions occurring at the working electrode but provide a consistent point of reference.
This consistency comes from their ability to maintain a stable electrode potential over time, which is achieved through their unique construction and the materials used. Common types of reference electrodes include the standard hydrogen electrode (SHE), the calomel electrode, and the silver/silver chloride (Ag/AgCl) electrode. Each has its own specific applications and advantages, depending on the experimental conditions.

mercury chloride reaction

The calomel electrode operates based on the reaction between mercury (Hg) and mercury(I) chloride (Hg2Cl2), commonly known as calomel. This reaction occurs within a saturated solution of potassium chloride (KCl).
The half-cell reaction can be written as: {Hg2Cl2 (s) + 2e^- ↔ 2Hg (l) + 2Cl^- (aq) }. This reaction is fundamental to the electrode's function because it determines the potential of the calomel electrode.
In this setup, mercury acts as the electrode surface, and the mercury chloride in KCl solution provides a stable environment for the reaction. The chloride ions from KCl solution help maintain a constant activity of Cl^- ions, ensuring the electrode potential remains stable.
Understanding this reaction is key to recognizing how the calomel electrode achieves its stability and reliability as a reference electrode.

stable electrode potential

A stable electrode potential is critical for reference electrodes, like the calomel electrode, because it ensures accurate measurements of other electrode potentials.
Stability in this context means that the potential does not change significantly over time or with small changes in environmental conditions such as temperature or pressure.
The calomel electrode achieves this stability through its specific chemical composition and the use of a saturated KCl solution.
The stable potential is a result of the well-defined mercury/mercury(I) chloride reaction. The saturated KCl solution helps maintain a constant chloride ion concentration, which is crucial for the stability of the electrochemical reaction occurring at the electrode.

• For precise electrochemical measurements, having a stable reference point is essential.
• The calomel electrode's design ensures that it can be used as a reliable reference in various electrochemical setups.