Lattice Enthalpy — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Lattice Enthalpy.

Born-Haber Cycle for Complex Ionic Compounds

medium

While simple MX type compounds are common, NEET might introduce slightly more complex compounds like $M_2X$ or $MX_2$ (e.g., $Na_2O$, $CaF_2$). This would require students to correctly account for multiple ionization enthalpies, multiple electron gain enthalpies, and appropriate stoichiometric coefficients for dissociation enthalpies. The challenge lies in setting up the cycle correctly and performing accurate calculations with more terms.

Interplay with Hydration Enthalpy and Solubility

high

Lattice enthalpy and hydration enthalpy are two sides of the same coin when discussing solubility. Questions are highly likely to involve comparing these two energy terms to predict or explain the solubility trends of ionic compounds in water. For instance, why certain compounds are soluble despite high lattice enthalpy (due to even higher hydration enthalpy) or vice-versa. This tests a deeper conceptual understanding beyond just calculation.

Qualitative Comparison of Lattice Enthalpy with Multiple Factors

high

Questions asking to rank or compare lattice enthalpies of compounds where both charge and size vary are common. For example, comparing LiF, NaCl, MgO, and $Al_2O_3$. Students need to correctly identify that charge is the dominant factor, followed by size. Misinterpreting this hierarchy is a common trap. Such questions test the application of the $q_1 q_2/r$ principle effectively.