CHAPTER 23 – ENERGY IN CHEMICAL REACTIONS Energy profile diagram for an endothermic reaction
The energy profile diagram in Fig. 23.7 shows an endothermic reaction. Notice that the products of the reaction have more energy than the reactants. This is because energy has been taken in during the reaction.
Activation energy
Products
Energy taken in
) Fig. 23.7 Energy profile diagram of an endothermic reaction
Reactants
Reaction progress The effect of a catalyst
We know that a catalyst speeds up the rate of a chemical reaction by lowering the amount of activation energy needed for particles to react.
The effect of a catalyst on a chemical reaction can be seen in the energy profile diagram in Fig. 23.8.
Activation energy without catalyst
Activation energy with catalyst
Reactants
) Fig. 23.8 Energy profile diagram to show the effect of a catalyst on a chemical reaction
Reaction progress ? TEST TUBE 3. Is the reaction shown in Fig. 23.8 exothermic or endothermic? Explain your answer. Elements of Science 227