The correct answer indicated by 'A' for the endothermic and exothermic reaction is C. +Ea
What is the diagram about?
The letter 'A' points to a segment of the curve that represents the difference in energy between the reactants and the top of the curve, which is the energy barrier that must be overcome for the reaction to proceed. This is known as the activation energy.
In the context of the options:
"Ea" typically stands for activation energy.
The "+" or "–" signs indicate whether energy is being absorbed or released.
Since 'A' is pointing upwards from the reactants to the peak of the curve, this suggests an input of energy is required to reach the transition state, which is characteristic of the activation energy of the reaction.
Therefore, the correct answer would be:
C. +Ea
This signifies that 'A' is indicating a positive activation energy, which is the energy required to initiate the reaction.