5.1.7—Enthalpy changes from appropriate experimental

In a calorimetry experiment, measure the temperature change of a known mass and use q=mcΔT to estimate heat transferred. Divide by moles reacting to obtain an enthalpy change per mole.

Record the sign correctly: if the surroundings warm, the reaction is exothermic and ΔH is negative. Account for the solution’s mass, specific heat capacity and the limiting amount reacted.

If 100 g of solution warms by 5.0 °C and c=4.18 J g⁻¹ K⁻¹, q=2090 J absorbed by the solution; the reaction released −2090 J before dividing by reacting moles.

The measured temperature change is not itself ΔH. Heat capacity, mass, units and the amount of substance all enter the calculation.