Reaction Profiles

Reaction profiles, also known as energy level diagrams, provide a visual representation of the energy changes that take place during chemical reactions.

On a reaction profile:

  • The X-axis represents the progress of the reaction
  • The Y-axis represents the energy of the reactants and products

When reactant particles collide with enough energy, a chemical reaction occurs. The minimum amount of energy required for a reaction to take place is the activation energy.

This is represented by the initial increase in energy on the reaction profile. This activation energy is necessary to overcome the energy barrier that prevents the reactants from transforming into products.

Exothermic and Endothermic Reaction Profiles

On a reaction profile, you can determine if a reaction is exothermic or endothermic by looking at the energy of the reactants and products.

Exothermic reactions are those that release energy to the surroundings, resulting in a decrease in energy from the reactants to the products. In other words, the energy of the products is lower than that of the reactants.

In contrast, endothermic reactions absorb energy from the surroundings, resulting in an increase in energy from the reactants to the products. Therefore, the energy of the products is greater than that of the reactants.

Exothermic Reaction

The diagram below shows a reaction profile for an exothermic reaction.

An exothermic reaction graph shows the energy of the products first plateauing, then rising, and finally dipping to a point lower than the starting energy before plateauing again.

The energy of the products is lower than that of the reactants. This is because the reaction releases energy, resulting in a negative energy change.

Endothermic Reaction

The diagram below shows a reaction profile for an endothermic reaction.

An endothermic reaction graph depicts the energy of the products initially plateauing, subsequently rising, slightly dipping, and finally plateauing at a level higher than the starting point.

The energy of the products is higher than that of the reactants. This is because the reaction absorbs energy, resulting in a positive energy change.

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