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Thermodynamics typically contributes 1-2 questions in JEE Main (approximately 4.7% weightage). Common question types: (1) Hess's law calculation using formation or bond enthalpies — straightforward application, 2-3 minutes. (2) Spontaneity prediction — given delta_H and delta_S, find the temperature range for spontaneity. T = delta_H/delta_S. Watch unit conversion (kJ vs J). (3) Born-Haber cycle — calculate lattice energy. Set up the cycle carefully, include all steps. (4) delta_H vs delta_U — count only gaseous species for delta_ngas. (5) Work calculations — know when to use -P_ext*delta_V vs -nRT ln(V2/V1). Common traps: mixing up kJ and J in T = delta_H/delta_S; forgetting that H2O(l) is not counted in delta_ngas; using products-reactants for bond energies (it's broken-formed); confusing delta_G = 0 (equilibrium) with delta_G_standard = 0 (K = 1). Quick checks: exothermic + entropy increase = always spontaneous; endothermic + entropy decrease = never spontaneous. At the boiling/melting point, delta_G = 0 (equilibrium between phases). Memorise: neutralisation enthalpy = -57.1 kJ/mol for strong acid-strong base.