Equilibrium

A high-weight Physical Chemistry unit for JEE Main 2027 (typically 5-6% of the paper). It covers physical and chemical equilibria, the law of mass action ($K_c$, $K_p$), Le Chatelier's principle and ionic equilibrium — acids and bases, Ostwald's dilution law, pH, buffers, the common-ion effect, salt hydrolysis and solubility product.