 |
Enthalpy is the term used in Chemistry for the chemical potential energy of a substance (there is a slight difference between the two measures, but for Higher this difference can be ignored). It is given the symbol H. It is not possible to directly measure the enthalpy of a chemical, however during a chemical reaction, the enthalpy change can be measured in kilojoules (kJ). The enthalpy change is given the symbol ΔH.
The enthalpy change is calculated from the difference in enthalpy between the enthalpy of the products (Hp) and the reactants (Hr).
ΔH = Hp – Hr
The calculation is product minus reaction, which means that enthalpy changes can be positive or negative. If the enthalpy change for one mole of substance is calculated, then the enthalpy change is expressed in kJ.mol-1. Enthalpy change can be calculated from the potential energy diagram. |
