The enthalpy change (\( \Delta H \)) of a chemical reaction can be determined from an energy profile graph by calculating the difference in energy between the reactants and products. The formula can be expressed as:
\[ \Delta H = H_{\text{products}} - H_{\text{reactants}} \]
Where:
- \( H_{\text{products}} \) is the total enthalpy of the products,
- \( H_{\text{reactants}} \) is the total enthalpy of the reactants.
In an energy profile graph:
- The reactants are typically represented on the left side,
- The products are on the right side,
- The vertical axis represents the enthalpy (or potential energy),
- The activation energy can also be noted as the energy difference between the reactants and the peak of the energy barrier (transition state).
If the resulting value of \( \Delta H \) is positive, it indicates an endothermic reaction (absorbing heat), while a negative value indicates an exothermic reaction (releasing heat).