Enthalpy Profiles:An enthalpy profile is when a plot is drawn of a reactions progress against the enthalpy. They show the energy changes that take place during a reaction. The highest peak on the graph shows the point in the reaction where the old bonds are stretched and broken and new bonds have started to form. The curve on the graph below applies to a simple one step reaction however many reactions take place in a series of steps and drawing a single curve would be meaningless. I will draw a enthalpy profile for the Harcourt Essen reaction however the enthalpy profile will be different due to a greater number of steps.

The difference in endothermic and exothermic reactions can be seen in their respective enthalpy profiles as the energy of the products is higher than the reactants towards the end of a reaction in a endothermic reaction due to heat being absorbed from the surrounding whereas the opposite is true for the exothermic reactions. When a catalyst is added to a reaction, the change in energy can also be seen in a enthalpy profile as the catalyst provides a different pathway for the reaction so that less energy is needed during the collision for products to be made. The enthalpy profile of an endothermic reaction with a catalyst can be seen below. After adding a catalyst to my reaction I will also draw an enthalpy profile to compare to my previous one.