Question

consider a hypothetical chemical reaction: a + b → c + d (in this equation a, b, c and d stand for some unknown chemical formulas.) here is an energy diagram for the reaction: energy - reaction coordinate diagram description use the energy diagram to answer these questions. what is the heat of reaction? kj/mol is the reaction exothermic or endothermic? exothermic endothermic neither can you determine the activation energy? yes, its kj/mol no. can you determine the activation energy of the reverse reaction? c + d → a + b yes, its kj/mol no.

Explanation:

Step1: Calculate heat of reaction

Heat of reaction ($\Delta H$) is energy of products - energy of reactants. From the graph, energy of reactants ($A + B$) is 300 kJ/mol and energy of products ($C + D$) is 100 kJ/mol. So, $\Delta H=100 - 300=- 200$ kJ/mol.

Step2: Determine reaction type

Since $\Delta H<0$, heat is released. So the reaction is exothermic.

Step3: Find activation energy

Activation energy ($E_a$) is the energy difference between the transition - state and the reactants. The highest point on the energy curve is around 400 kJ/mol and energy of reactants is 300 kJ/mol. So $E_a = 400 - 300=100$ kJ/mol.

Step4: Find reverse activation energy

For the reverse reaction $C + D
ightarrow A + B$, the activation energy is the energy difference between the transition - state and the products. The highest point on the energy curve is 400 kJ/mol and energy of products ($C + D$) for the reverse reaction is 100 kJ/mol. So $E_{a - reverse}=400 - 100 = 300$ kJ/mol.

Answer:

What is the heat of reaction? -200 kJ/mol
Is the reaction exothermic or endothermic? Exothermic
Can you determine the activation energy? Yes, it's 100 kJ/mol
Can you determine the activation energy of the reverse reaction $C + D
ightarrow A + B$? Yes, it's 300 kJ/mol