Use the formula: ΔH = Hproducts − Hreactants
For a reaction at constant pressure, use q = ΔH
Measure the heat absorbed or released by the reaction
Calculate using calorimetry: q = mcΔT
Determine the mass of the solution or substance, m
Use the specific heat capacity, c
Measure the temperature change, ΔT
Apply the sign convention:
Positive ΔH for endothermic reactions
Negative ΔH for exothermic reactions
Use bond enthalpies: ΔH = Σ(bonds broken) − Σ(bonds formed)
Use standard enthalpies of formation: ΔH°rxn = ΣΔH°f(products) − ΣΔH°f(reactants)
Use Hess’s law if the reaction can be split into steps
Add the enthalpy changes of the steps to get the total ΔH
Convert units to kJ/mol if needed
Divide total heat by moles of limiting reactant to get enthalpy change per mole