Standard Enthalpy of Formation — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Standard Enthalpy of Formation.

Calculation of $\Delta H_{rxn}^\circ$ for a biological reaction

medium

NEET often integrates chemistry concepts with biological relevance. A question might involve calculating the enthalpy change for a metabolic reaction (e.g., glucose oxidation, ATP hydrolysis) where $\Delta H_f^\circ$ values for the relevant biomolecules are provided. This tests the core calculation skill but in a slightly different context, requiring students to recognize the balanced biochemical equation.

Identifying the correct formation reaction for a compound with multiple allotropes or common non-standard states

high

This is a classic conceptual trap. Questions often present options where elements are in non-standard states (e.g., $\text{C}(\text{diamond})$ instead of $\text{C}(\text{graphite})$, $\text{O}(\text{g})$ instead of $\text{O}_2(\text{g})$) or where more than one mole of product is formed. A question specifically asking to identify the *incorrect* statement regarding $\Delta H_f^\circ$ for such cases is highly probable, testing the precise definition.

Combined problem involving $\Delta H_f^\circ$ and bond energies

low

While less common, a challenging question could combine the calculation of $\Delta H_{rxn}^\circ$ using $\Delta H_f^\circ$ values with a separate calculation using average bond energies. Students might be asked to compare the results or use one method to find a missing value for the other. This tests a broader understanding of thermochemistry and the different ways to estimate enthalpy changes.