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:

use the energy diagram to answer these questions.

what is the heat of reaction? -50 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 = energy of products - energy of reactants. From the graph, energy of \(A + B\) (reactants) is 200 kJ/mol and energy of \(C + D\) (products) is 150 kJ/mol. So, \(\Delta H=150 - 200=- 50\) kJ/mol.

Step2: Determine reaction type

Since \(\Delta H=-50\) kJ/mol (negative), heat is released. So, the reaction is exothermic.

Step3: Calculate activation energy

Activation energy is the energy difference between reactants and the transition - state. The energy of reactants (\(A + B\)) is 200 kJ/mol and the maximum energy (transition - state) is 300 kJ/mol. So, \(E_{a}=300 - 200 = 100\) kJ/mol.

Step4: Calculate reverse reaction activation energy

For the reverse reaction \(C + D
ightarrow A + B\), activation energy is the energy difference between products (\(C + D\), energy = 150 kJ/mol) and the transition - state (energy = 300 kJ/mol). So, \(E_{a(\text{reverse})}=300 - 150=150\) kJ/mol.

Answer:

-50 kJ/mol, Exothermic, Yes, it's 100 kJ/mol, Yes, it's 150 kJ/mol