How to use the hess's law enthalpy calculator
Sum step enthalpies to find the overall reaction enthalpy. Enter step 1 enthalpy, step 1 multiplier, step 2 enthalpy, step 2 multiplier in the fields above; the overall enthalpy is computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- h1 — Step 1 enthalpy (kJ)
- f1 — Step 1 multiplier
- h2 — Step 2 enthalpy (kJ)
- f2 — Step 2 multiplier
Worked example
With step 1 enthalpy = -393.5 kJ, step 1 multiplier = 1, step 2 enthalpy = 285.8 kJ, step 2 multiplier = 2, the calculator gives overall enthalpy ≈ 178.1 kJ.
Frequently asked questions
What is the formula for the hess's law enthalpy calculation?
Overall enthalpy (kJ) = h1 × f1+h2 × f2. Here h1 is step 1 enthalpy (kJ), f1 is step 1 multiplier, h2 is step 2 enthalpy (kJ), f2 is step 2 multiplier.
What inputs do I need for the hess's law enthalpy calculator?
You need step 1 enthalpy in kJ, step 1 multiplier, step 2 enthalpy in kJ, step 2 multiplier. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.