Hess Law Enthalpy Calculator
Calculate reaction enthalpy from product and reactant enthalpies.
Hess Law Enthalpy measurements
Enter your values, then calculate.
Result
How to calculate hess law enthalpy
Hess's Law states that the total enthalpy change for a reaction is the same regardless of the path taken — this calculator finds reaction enthalpy from the sum of product and reactant enthalpies.
How the calculation works
ΔH(reaction) = Sum of product enthalpies − Sum of reactant enthalpies.
Example
Products totaling −850 kJ, reactants totaling −700 kJ: −850−(−700) = −150 kJ.
Frequently asked questions
How is Result calculated?
Result = [Sum of product enthalpies] − [Sum of reactant enthalpies].
Is the Hess Law Enthalpy Calculator free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Hess Law Enthalpy Calculator
ΔH(reaction) = Sum of product enthalpies − Sum of reactant enthalpies.
Let's understand your hess law enthalpy result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Hess Law Enthalpy
- Make sure enthalpy values are for the correctly balanced equation, with each compound's enthalpy multiplied by its stoichiometric coefficient.
- A negative result indicates an exothermic reaction (releases heat); positive indicates endothermic (absorbs heat).
Common Hess Law Enthalpy Mistakes to Avoid
- Forgetting to multiply each compound's standard enthalpy by its stoichiometric coefficient in the balanced equation before summing.
When to Use This Calculator
Hess's Law states that the total enthalpy change for a reaction is the same regardless of the path taken — this calculator finds reaction enthalpy from the sum of product and reactant enthalpies.