15.65 b [ENDORSED]

[Grace Ramey 2K]

15.65
For the reversible, one-step reaction 2A---><--- B + C, the forward rate constant for the formation of B is 265 L/mol x min and the rate constant for the reverse reaction is 392 L/mol x min. The activation energy for the forward reaction is 39.7 kJ/mol and that of the reverse reaction is 25.4 kJ/mol.

b. Is the reaction exothermic or endothermic?

I was confused about part b. I thought that if the forward reaction is endothermic, then the reverse reaction will be exothermic and vice versa? How can the entire reversible reaction be classified as one or the other? Also, the solutions manual says that the reaction is endothermic, but I couldn't quite understand how they came to that conclusion. Can someone explain?

Thank you for your help!

[Gianna Apoderado 1B]

I believe that when it asks about the reaction, it generally means the forward direction, unless otherwise stated. In this case, the reaction is endothermic because the activation energy of the forward direction is greater than the activation energy of the reverse reaction, which means that the forward reaction has to overcome a greater energy barrier to occur, which means it needs heat/is an endothermic reaction.