$word_{count}$: 200

Equilibrium accounts for approximately 6.5% of JEE Main chemistry — among the highest-weighted topics. Question types: (1) pH calculations of mixtures, buffers, or salt solutions (1-2 questions per exam). (2) Ksp-based precipitation or solubility problems (1 question). (3) Le Chatelier's principle application or K manipulation (1 question). Time: 2-3 minutes per question. Strategy: memorise all pH formulas (strong acid, weak acid, buffer, salt hydrolysis, amphoteric). For mixture problems, first determine what reacts completely $\frac{strong acid}{base neutralisation}$, then identify the resulting solution type (buffer, salt, excess acid/base). For Ksp: convert to molar solubility using correct stoichiometric formula. Never compare Ksp directly for different salt types. Common traps: pH of very dilute acids (10^-8 M HCl is not pH 8), K changes only with temperature, adding inert gas at constant volume has no effect, and the diprotic trap where second dissociation matters only at very low concentrations. Master Henderson-Hasselbalch — it covers buffer, half-equivalence point, and many mixing problems.