Enthalpy Change (Calorimetry) Calculator
Calculate the heat absorbed or released with q = m·c·ΔT, and the molar enthalpy change of a reaction.
How it works
q = m·c·ΔT · ΔH (per mole) = −q ÷ moles · q in joules, ΔH shown in kJ/mol
Calorimetry measures reaction heat from the temperature change of the surrounding solution. The heat q equals the solution's mass times its specific heat times the temperature change. If the solution warms up (positive ΔT) the reaction released heat, so the reaction's enthalpy ΔH is negative (exothermic); dividing −q by the moles of reactant gives the molar enthalpy change.
Worked example
A reaction warms 100 g of solution (specific heat 4.18 J/g·°C) by 5 °C, absorbing q = 100 × 4.18 × 5 = 2090 J = 2.09 kJ. For 0.1 mol of reactant, ΔH = −2.09 ÷ 0.1 = −20.9 kJ/mol (exothermic).
Sources: Calorimetry — Wikipedia
Frequently asked questions
Why is ΔH negative when the temperature rises?
A rising temperature means the reaction released heat into the solution. By convention an exothermic reaction has a negative enthalpy change, so ΔH carries a minus sign relative to the heat the solution gained.
What specific heat should I use?
For dilute aqueous reactions, water's value of about 4.18 J/g·°C is standard. Use the actual solution's specific heat if it differs significantly, and its total mass for m.
What if I do not know the moles?
Leave the moles field at 0 and the calculator reports only the total heat q in joules and kilojoules, skipping the per-mole enthalpy.
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