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In this chapter, the topic of Electrodes is explained through the concept of hydrogen electrodes. This electrode is built by bubbling H2 gas in acid (such as HCl, H2SO4, or another mineral acid).

The equilibrium in this case is represented as-

H+(aq)   +  e– ↔ 1 / 2 H2(g)

In this case, the electrode is reversible with respect to the H+ ion. H2 gas is non-conducting in nature hence noble metal like Pt is used for making electrical contact in the circuit and therefore the electrode is represented as-

Pt ; H2(g) | H+

and the electrode reaction is written as

2H+ (aq)   +  2e–—————–> H2(g)

If the acid in Pt foil dipped contains 1-mole concentration of (H+) ion at 25°C then the electrode is called hydrogen electrode.

Normal hydrogen electrode (NHE) or standard hydrogen electrode(SHE) is used as the reference electrode. However, it is not convenient to use normal hydrogen electrodes as reference electrode because of the following difficulties:

(i) Gases are difficult to handle

(ii) It is difficult to maintain the H+ ion concentration as 1M and the pressure of the gas at 1 atm.

(iii) The electrode is poisoned even by the presence of traces of impurities.

(2) Calomel electrode Hg- Hg2 Cl2 electrode:

Calomel electrode is simple and reliable. It is also used as reference electrode for determining electrode potentials and pH of the supplied solutions. This electrode consists of Hg, solid mercurous chloride; Hg2Cl2, and a saturated solution of KCl. This electrode is represented as-

Hg(I), Hg2Cl2(s); KCl (solution)

This electrode is reversible with respect to Cl– ions, i.e. when it acts as anode, the electrode reaction is written as

2Hg (1)  +  2 Cl (aq)——————————  Hg2Cl2(s)  +  2 e–

and when it acts as the cathode, the reverse reaction takes place. If the electrode reaction involves reduction, the Hg2(ous) ion derived by Hg2Cl2 would be discharged at the electrode, hence more and more of calomel would pass into the solution.

The Heisenberg uncertainty principle is a fundamental concept in quantum mechanics that describes the limits of our ability to measure certain pairs of physical quantities with arbitrary precision. It was first proposed by German physicist Werner Heisenberg in 1927 and represents a key development in our understanding of the quantum world.

The principle states that there is a fundamental limit to the precision with which we can simultaneously measure certain pairs of physical quantities, such as position and momentum, or energy and time. This is because the act of measuring one quantity necessarily disturbs the other, leading to an inherent uncertainty in our knowledge of both quantities.

The Heisenberg uncertainty principle has far-reaching implications in the fields of physics, chemistry, and beyond, providing a foundation for understanding the behavior of atoms, molecules, and subatomic particles. It has been used to explain a variety of phenomena, from the stability of atomic nuclei to the behavior of electrons in semiconductors

The de Broglie equation, also known as the matter-wave equation, is a fundamental equation in quantum mechanics that relates the wave-like properties of matter to its particle-like properties. It was first proposed by French physicist Louis de Broglie in 1924 and represents a key development in our understanding of the dual nature of matter.