Question

3. Energy Diagrams: Using the axes below, draw an energy diagram for an endothermic reaction. Label the following in your diagram: The reactants "The products "The activation energy "The total energy gained or lost by the reaction (AH) reaction progress

Answer 1

In an endothermic reaction, energy is absorbed by the reactants as they convert to products.

First, the reactants gain sufficient energy to go to a transition state by acquiring energy called 'activation energy'.

Hence, the difference in energy between the reactants and transition state is the activation energy E_a.

If a reactant molecule has energy equal to or greater than activation energy, it can cross the activation barrier and convert to product. The difference in energy between the product and the reactant is termed as $\Delta H.$ If the product is higher in energy than the reactant, then net energy is absorbed by the reaction from the surrounding meaning, the value of $\Delta H$ is positive for the endothermic reaction.

Hence, we can draw the reaction profile diagram with energy in y axis and reaction progress in x axis as follows:

(Transition state) Ea Products Energy Delta H Reactants Reaction Progress