Reaction Enthalpy Calculator
🔥 Thermochemistry & Bonding. Use the Reaction enthalpy (Hess) formula to find δh°rxn, σ δhf products, σ δhf reactants: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| ΔH°rxn | kJ/mol |
| Σ ΔHf products | kJ/mol |
| Σ ΔHf reactants | kJ/mol |
Worked example
Find the δh°rxn when Σ ΔHf products = -965 kJ/mol, Σ ΔHf reactants = -75 kJ/mol.
Using Δ H°rxn = Σ Δ H°f(prod) - Σ Δ H°f(react): ΔH°rxn = -890 kJ/mol.
Frequently asked questions
What is the formula for Reaction enthalpy (Hess)?
Δ H°rxn = Σ Δ H°f(prod) - Σ Δ H°f(react).
What do the letters stand for, and what units are used?
ΔH°rxn in kJ/mol, Σ ΔHf products in kJ/mol, Σ ΔHf reactants in kJ/mol.
How do you calculate δh°rxn?
Put the values into Δ H°rxn = Σ Δ H°f(prod) - Σ Δ H°f(react). For example, with Σ ΔHf products = -965 kJ/mol, Σ ΔHf reactants = -75 kJ/mol, δh°rxn = -890 kJ/mol.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (δh°rxn, σ δhf products, σ δhf reactants) and fill in the others: it rearranges the formula for you.
