Lattice Enthalpy — Prelims Strategy

Prelims Strategy

To excel in NEET questions on lattice enthalpy, a multi-pronged strategy is crucial. For numerical problems involving the Born-Haber cycle, first, write down the complete cycle equation, ensuring all steps (sublimation, ionization, dissociation, electron gain, lattice formation) are included with correct stoichiometry (e.

g., $rac{1}{2}Delta H_{diss}$ for diatomic elements, multiple IE/EA for polyvalent ions). Pay meticulous attention to the sign convention for each enthalpy change (endothermic +ve, exothermic -ve). Double-check arithmetic, as calculation errors are common.

For conceptual questions comparing lattice enthalpies, immediately identify the charges of the ions. The product of charges ($q_1 q_2$) is the most dominant factor; higher product means higher lattice enthalpy.

If charges are identical, then consider ionic radii; smaller ions lead to higher lattice enthalpy. For questions on definitions and properties, remember that lattice enthalpy is an indirect measurement, typically exothermic for formation, and directly related to melting point and hardness.

Be wary of trap options that confuse lattice enthalpy with enthalpy of formation or bond dissociation enthalpy. Practice with a variety of problems to build speed and accuracy.