Heat of Reaction Calculator Formula

Understand the math behind the heat of reaction calculator. Each variable explained with a worked example.

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Formulas Used

Heat of Reaction per Mole

heat_per_mole = heat_kj / moles

Variables

VariableDescriptionDefault
heat_kjTotal Heat Measured (q)(kJ)-50
molesMoles of Limiting Reagent(mol)0.1

How It Works

Heat of Reaction per Mole

Formula

ΔH_rxn = q / n

Where:

  • ΔH_rxn = heat of reaction per mole (kJ/mol)
  • q = total heat measured (kJ), negative for exothermic
  • n = moles of limiting reagent

    • This converts calorimetry data into a molar enthalpy value for the reaction.

    Worked Example

    A reaction releases 50 kJ of heat using 0.1 mol of limiting reagent.

    heat_kj = -50moles = 0.1
    1. 01ΔH_rxn = q / n
    2. 02ΔH_rxn = -50 / 0.1
    3. 03ΔH_rxn = -500 kJ/mol

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