Calomel Electrode | Construction and Working

Summary

In this informative video, Mr. Abhijeet explains the construction, working, and applications of the calomel electrode, a widely used reference electrode in electrochemistry. He covers its key components, such as the glass tube, mercury pool, and potassium chloride solution, and how these elements work together to maintain a stable reference potential. The electrode's reversible reactions and use in potentiometric measurements, pH testing, and corrosion studies are also discussed. Viewers will learn how the calomel electrode provides reliable and reproducible measurements, making it essential in various electrochemical applications.

Takeaways

• 😀 The Calomel Electrode is a secondary reference electrode used in electrochemistry for providing stable and reproducible reference potentials.
• 😀 It consists of a glass tube filled with a saturated potassium chloride (KCl) solution and a mercury pool at the bottom.
• 😀 The mercury pool is in contact with a paste of mercury chloride (Hg₂Cl₂), known as calomel, which helps maintain the stability of the electrode.
• 😀 A platinum wire is inserted into the KCl solution to establish an electrical contact with the electrode.
• 😀 The electrode can function as both an anode and a cathode depending on the electrochemical reaction being carried out.
• 😀 The Calomel Electrode maintains a constant potential by establishing an equilibrium between mercury ions and chloride ions.
• 😀 It is used in various applications such as pH measurement, potentiometric titrations, corrosion studies, and as a secondary reference electrode in many electrochemical cells.
• 😀 Under standard conditions (25°C and 1 atm), the standard potential of the Calomel Electrode is +0.242 V.
• 😀 The electrode’s potential is influenced by the concentration of chloride ions, temperature, and pressure conditions.
• 😀 The reversibility of the reactions at the Calomel Electrode ensures it can repeatedly produce the same reference potential, making it reliable for precise electrochemical measurements.

Q & A

What is a calomel electrode?

A calomel electrode is a secondary reference electrode used in electrochemical measurements. It provides a stable and reproducible potential against which the potential of other electrodes can be measured.

What is the main purpose of the calomel electrode in electrochemistry?

The calomel electrode is mainly used to establish a stable reference potential in electrochemical cells. It is used in potentiometric measurements and other applications where a consistent reference potential is required.

What is the construction of a calomel electrode?

The calomel electrode consists of a glass tube filled with a potassium chloride (KCl) solution, a mercury pool at the bottom, and a paste of mercury(II) chloride (HgCl₂) and mercury, known as calomel paste. A platinum wire is inserted for electrical contact.

What is the role of the mercury pool and calomel paste in the calomel electrode?

The mercury pool and calomel paste form the interface between mercury, mercury chloride, and potassium chloride solution. They help establish an equilibrium, which is essential for determining the electrode potential.

Why is the calomel electrode often used as a reference electrode?

The calomel electrode is used as a reference electrode because it provides a stable and reproducible potential that can be reliably used to measure the potential of other electrodes in an electrochemical cell.

How does the calomel electrode work?

The calomel electrode works by maintaining an equilibrium between the mercury pool, mercury(II) chloride, and the potassium chloride solution. The electrode potential is determined by this equilibrium, and the reactions at the electrode can either be oxidation or reduction, depending on the setup.

What is the standard electrode potential of the calomel electrode?

Under standard conditions (25°C and 1 atm pressure), the standard electrode potential of the calomel electrode is +0.242 V.

What are the oxidation and reduction reactions that occur at the calomel electrode?

At the calomel electrode, the oxidation reaction (when acting as the anode) is: Hg → Hg²⁺ + 2e⁻, and the reduction reaction (when acting as the cathode) is: Hg²⁺ + 2e⁻ → Hg.

What factors affect the potential of the calomel electrode?

The potential of the calomel electrode depends on factors such as the concentration of chloride ions in the potassium chloride solution, temperature, and pressure. The potential also varies when it is used in non-standard conditions.

What are the primary applications of the calomel electrode?

The calomel electrode is used in pH measurement, potentiometric titrations, corrosion studies, and electrochemical research. It serves as a secondary reference electrode in many electrochemical cells.