The given graphs are Reaction Coordinate Diagrams which depict the conversion of reactants into products.
Diagram 1: Represents an exothermic reaction. These reactions proceed with the release of heat energy as a result the energy of the products is lower than the reactants.
Diagram 2: Represents an endothermic reaction. In contrast, these reactions proceed with the absorption of heat energy as a result the energy of the products is higher than the reactants.
In both diagrams, there is a peak or a hump which corresponds to the activation energy for the reaction. This is the minimum amount of energy required by the reactants as they collide to form the products.
The peaks on the graphs in the given figure represent the [tex]\boxed{{\text{activation energy}}}[/tex].
Further explanation:
Endothermic reaction
It is the type of chemical reaction that requires the absorption of heat from the surroundings in order to proceed itself. Due to heat absorption, these reactions lead to a decrease in the temperature of the system. Such reactions cannot occur spontaneously. These are characterized by positive heat flow and therefore the enthalpy change during these reactions comes out to be positive.
Exothermic reaction
It is the chemical reaction that involves the release of energy in the form of heat or light. It is just the reverse of endothermic reactions. Due to the release of energy, these reactions lead to an increase in the temperature of the system. Such reactions can occur spontaneously. These are characterized by negative heat flow and therefore the enthalpy change during these reactions comes out to be negative.
Activation energy is the minimum amount of energy that is needed by the reactant molecules so as to undergo a chemical reaction. The energy absorbed in the case of endothermic reactions or the energy released in exothermic reactions provides the activation energy to progress the chemical reaction.
Figure 1 represents the reaction coordinate diagram for an exothermic reaction. Here, reactants have higher energy than that of products. So energy is released by the reactants so as to convert them into the products and complete the chemical reaction. The peak in this diagram refers to the activation energy required for the completion of the reaction.
Figure 2 represents the reaction coordinate diagram for an endothermic reaction. Here, reactants have lower energy than that of products. So energy is supplied to the reactant molecules in order to get converted into the products. The peak in this diagram also refers to the activation energy required for the completion of the reaction.
Therefore the peak in both the diagram indicates the activation energy required for the completion of the respective reactions.
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Answer details:
Grade: Senior School
Chapter: Thermodynamics
Subject: Chemistry
Keywords: endothermic, exothermic, peaks, activation energy, enthalpy change, reactants, products.
