Electrochemistry

Electrochemistry is the bridge between chemical reactions and electrical energy — and a chapter that reliably delivers 6-8 Board marks and 2-3 JEE/NEET questions every year. We build the whole subject from the Daniell cell upward: how a spontaneous redox reaction in a galvanic cell pushes electrons through a wire to do electrical work, how we measure electrode potentials against the standard hydrogen electrode and arrange them into the electrochemical series, and how the Nernst equation $E = E^\circ - \frac{0.059}{n}\log Q$ links cell potential to concentration. From there we connect potential to thermodynamics ($\Delta_r G^\circ = -nFE^\circ_{cell}$ and $E^\circ_{cell} = \frac{0.059}{n}\log K_c$), study how solutions conduct electricity (conductivity, molar conductivity, cell constant, and Kohlrausch's law of independent migration of ions), reverse the process in electrolytic cells using Faraday's two laws of electrolysis, and finish with the real-world payoff: primary and secondary batteries (dry cell, mercury cell, lead storage, nickel-cadmium), hydrogen-oxygen fuel cells, and the electrochemistry of corrosion and rusting. Every formula, every electrode-potential sign convention, and every numerical technique an exam can ask is covered here.