Enthalpy Changes and Bond Energies
Learn to calculate enthalpy changes for reactions using bond enthalpies, enthalpy of formation, and Hess's law.
Why this shows up in the exam
You will be tested on your ability to use enthalpy data to solve for unknowns in reaction energetics.
How NEET tests this
Practise it
These are real questions from past NEET papers that test this exact idea.
Given that bond energies of H – H and Cl – Cl are 430 kJ mol⁻¹ and 240 kJ mol⁻¹ respectively and ΔHₓ for HCl is -90 kJ mol⁻¹, bond enthalpy of HCl is
Push further
More challenging14 harder questions built from the past papers above — a step up in difficulty, with distractors designed so you can't get there by elimination. Written and checked by our reviewers, not from a real paper.
Given the bond dissociation enthalpies: H-H = 436 kJ/mol, F-F = 158 kJ/mol, and H-F = 568 kJ/mol. Calculate the standard enthalpy of formation of HF(g).
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