We can define enthalpy as a concept used in science and engineering when heat and work need to be calculated or simply the sum of the system’s internal energy and the product of its pressure and volume.
Measuring the change in enthalpy allows us to determine whether a reaction was endothermic or exothermic.
Formula to calculate enthalpy.
When burning benzoic acid the heat evolved was -768 joules, if it was 1 atm and the volume of the acid was 122 cubic meters, calculate the enthalpy.
Therefore, the enthalpy is -646 J.