5.1.3 Reaction Profiles

Understanding Reaction Profiles

• Y-Axis (Energy Level): Represents the energy of the system.
• X-Axis (Reaction Progress): Represents the progress of the reaction from reactants to products.

Exothermic Reaction Profiles

In exothermic reactions, the energy stored in the reactants is higher than the energy stored in the products. This means:

• The reactants are drawn at a higher level along the y-axis compared to the products.
• The difference in height between the reactants and products represents the energy released to the surroundings during the reaction.

The reaction profile includes a "hump," which represents the activation energy. This is the minimum energy required to start the reaction:

• The height of the hump above the reactants indicates the energy needed for the reactants to collide with sufficient force to react.
• Once the reactants overcome this activation energy, the reaction proceeds, releasing energy.

Endothermic Reaction Profiles

In endothermic reactions, the energy stored in the products is higher than the energy stored in the reactants. This means:

• The reactants are drawn at a lower level along the y-axis compared to the products.
• The difference in height between the reactants and products represents the energy absorbed from the surroundings during the reaction.

Like in exothermic reactions, the reaction profile features a hump representing the activation energy:

• The height of the hump above the reactants indicates the energy required for the reactants to collide and react.
• For the reaction to occur, the system must absorb enough energy to overcome this activation energy barrier.