Question

The graph shows the reaction pathway for the reaction Q + R N + M. Interpret the graph by describing what each of the letters (A through G) represents and by explaining whether the reaction is endothermic or exothermic and how you know.

Answer 1

Answer: The reaction is exothermic reaction as the energy of products is less than the energy of reactants.

Explanation: Exothermic reactions are defined as the reactions in which energy of the product is less than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

Labeling of the parts in the diagram:

A represents the activation energy which is the energy required by reactants to cross the energy barrier to get converted to products.

E represents the potential energy of the reactants.

B represents the activated complex.

D represents the potential energy of the products.

C represents the total enthalpy change of the reaction, which comes out to be negative for exothermic reactions.

$\Delta H=E_P-E_R$

Answer 2

The letter A represents the amount of energy that must be added to the reactants which are at energy level F, so that they may be have their energy raised to level B, from where the reaction can occur.
The letter G shows the products, and it is visible that they are at a lower energy level than the reactants were. This means that in order to get from the higher energy to the lower energy, the reactants must release energy. Therefore, this reaction is exothermic.