1. Electrochemical Cells and Nernst Equation

Electrochemical cells convert chemical energy into electrical energy (galvanic cells) or vice versa (electrolytic cells). A galvanic cell consists of two half-cells, each with an electrode and an electrolyte, connected by a salt bridge and an external circuit. The potential difference generated is the cell potential ($E_{\text{cell}}$). The Nernst Equation relates the cell potential to the concentrations of reactants and products and the temperature: $E_{\text{cell}} = E^\circ_{\text{cell}} - \frac{RT}{nF} \ln Q$, allowing calculation of potential under non-standard conditions.

2. Conductance Of Electrolytic Solutions

Electrolytic solutions conduct electricity due to the presence of mobile ions. Conductance is the reciprocal of resistance and measures how easily current flows. Molar conductivity ($\Lambda_m$) is the conductance of a solution containing one mole of electrolyte. For weak electrolytes, molar conductivity increases significantly with dilution, as more ions become free. Kohlrausch's Law states that the molar conductivity of an electrolyte at infinite dilution is the sum of the contributions of its individual ions, enabling calculation of molar conductivities for weak electrolytes.

3. Electrolytic Cells and Electrolysis

Electrolytic cells use electrical energy to drive non-spontaneous chemical reactions, a process called electrolysis. In electrolysis, oxidation occurs at the anode (positive electrode) and reduction at the cathode (negative electrode). Faraday's Laws of Electrolysis quantify the amount of substance deposited or liberated at the electrodes: the mass deposited is directly proportional to the quantity of electricity passed ($m = ZIt$, where $Z$ is the electrochemical equivalent). This principle is used in electroplating and the production of metals like aluminum.

4. Batteries and Fuel Cells

Batteries are galvanic cells designed for practical energy storage and supply. Common types include primary batteries (non-rechargeable) like dry cells and secondary batteries (rechargeable) like lead-acid and lithium-ion batteries. Fuel cells are electrochemical devices that convert chemical energy from a fuel (often hydrogen) directly into electrical energy through a chemical reaction with an oxidizing agent (like oxygen), without combustion. They are highly efficient and produce minimal environmental pollution, representing a promising clean energy technology for India's future.

5. Corrosion (Electrochemical Theory)

Corrosion, particularly the rusting of iron, is an electrochemical process. It involves the oxidation of a metal and the reduction of an oxidizing agent (like oxygen). For iron, the process begins with the formation of a small electrochemical cell on the metal surface, where iron acts as the anode and gets oxidized. Oxygen acts as the cathode and gets reduced. The presence of electrolytes (like moisture and dissolved salts) accelerates corrosion. Understanding this electrochemical theory helps in developing methods for corrosion prevention, such as galvanization or using protective coatings.