NEET Chemistry - 02 Energy, Solutions and Equilibrium

Why do some reactions “want” to happen while others refuse—yet both can be painfully slow? If thermodynamics has ever felt like a maze of signs, symbols, and exceptions, this guide helps you draw the map and follow it. You’ll start by learning how to define a system, surroundings, and boundary in real chemical situations—and how that choice controls sign conventions for heat and work. From there, you’ll sort quantities into extensive vs. intensive properties and state vs. path functions, using clear comparisons (like altitude vs. the path you walk). Common process types—isothermal, adiabatic, isobaric, isochoric, cyclic, reversible, and irreversible—are explained with the key “what becomes zero?” shortcuts students often mix up. Next, the First Law becomes usable: pressure–volume work, thermochemical equations, standard states, and the difference between ΔU and ΔH (including why bomb calorimeters give constant-volume heat). You’ll also learn the pattern behind standard enthalpy changes, apply Hess’s law, and connect spontaneity to entropy, Gibbs energy, and equilibrium constants. The second half strengthens your equilibrium toolkit: concentration units, Raoult’s law and deviations, colligative properties and the van’t Hoff factor, dynamic equilibrium, Kc/Kp, reaction quotient, and Le Chatelier’s principle. Finally, you’ll build confidence with acids and bases—pH, Ka/Kb, buffers (Henderson–Hasselbalch), salt hydrolysis, and Ksp-based precipitation decisions.