Heat of Reaction Calculator
Calculate the standard enthalpy of reaction (ΔH) from formation enthalpies of reactants and products using Hess's Law.
Inputs
kJ/mol
mol
kJ/mol
mol
kJ/mol
mol
kJ/mol
mol
Results
Heat of Reaction (ΔH)
-457.2 kJ
Total Heat Released/Absorbed
457.2 kJ
Exothermic?1 (1 = yes, 0 = no)
Heat per Mole of Product-152.4 kJ/mol
How to Use This Calculator
- Look up the Standard Enthalpy of Formation (ΔHf) in kJ/mol for each reactant and product from NIST WebBook or CRC Handbook. Elements in their standard state have ΔHf = 0.
- Enter Reactant 1 ΔHf and its stoichiometric coefficient (moles in the balanced reaction equation).
- Enter Reactant 2 ΔHf and moles — set to 0 if there is only one reactant.
- Enter Product 1 ΔHf and moles, then Product 2 ΔHf and moles (set to 0 if only one product).
- Read the Heat of Reaction (ΔH) in kJ — negative values indicate an exothermic reaction (releases heat); positive values indicate endothermic (requires heat input).
- Use Total Heat Released/Absorbed to size reactor cooling or heating systems and evaluate thermal runaway risks.
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