Enthalpy of Reaction

Thermodynamics is the study of heat and its relation to energy and work. One of the most important thermodynamic properties is enthalpy, which indicates the heat energy transferred by a process at constant pressure. Enthalpy is used to describe chemical reactions, where the enthalpy change, ΔH, tells us how much heat is absorbed or released during a chemical reaction.

Enthalpy is a state function, meaning that the change is independent of the path and only takes into account the initial and final state. Thus, the ΔH of a reaction is calculated by subtracting the sum of the enthalpies of the reactants from the sum of the enthalpies of the products.

If ΔH is positive, the reaction is endothermic and absorbs heat from the surroundings. If ΔH is negative, the reaction is exothermic and releases heat to the surroundings.

We can measure the enthalpy change of a reaction using an isolated system like a calorimeter. A simplified calorimeter, like the one we have here, consists of an insulated sample cell with a stirrer and a thermometer. As the reaction proceeds inside of the insulated cell, the temperature changes and we are able to measure ΔT.

We can assume that no energy is transferred