Enthalpy Change Calculator
Calculate enthalpy change for chemical reactions
Table of Contents
How to Use
- Enter the total enthalpy of products in kJ/mol
- Enter the total enthalpy of reactants in kJ/mol
- Click Calculate to find the enthalpy change
- See if the reaction is exothermic (releases heat) or endothermic (absorbs heat)
What is Enthalpy?
Enthalpy (H) is a thermodynamic property that represents the total heat content of a system. In chemistry, we're usually interested in enthalpy changes (ΔH) during chemical reactions.
The formula for enthalpy change is: ΔH = H(products) - H(reactants)
Exothermic vs Endothermic
Exothermic reactions (ΔH < 0) release energy to surroundings, making them feel hot. Examples include combustion and neutralization reactions.
Endothermic reactions (ΔH > 0) absorb energy from surroundings, making them feel cold. Examples include photosynthesis and melting ice.
Frequently Asked Questions
- What does a negative enthalpy change mean?
- A negative ΔH means the reaction is exothermic and releases heat to the surroundings. The products have less stored energy than the reactants.
- What does a positive enthalpy change mean?
- A positive ΔH means the reaction is endothermic and absorbs heat from the surroundings. The products have more stored energy than the reactants.
- What are the units for enthalpy?
- Enthalpy is typically measured in kilojoules per mole (kJ/mol) or joules per mole (J/mol).