Can you describe at least 4 ways a catalyst can lower the activation energy of a reaction?
To see how a catalyst accelerates the reaction, we need to look at the potential energy diagram shown below which compares the non-catalytic and the catalytic reaction. For the non-catalytic reaction, the figure is simply the familiar way to visualize the Arrhenius equation: the reaction proceeds when A and B collide with succificient energy to overcome the activation barrier. The change in Gibbs free energy between reactants, A + B, and the product P is delta G. The catalytic reaction starts by bonding of the reactants A and B to the catalyst, in a spontaneous reaction. Hence, the formation of this complex is exothermic and the free energy is lowered. There then follows the reaction between A and B while they are bound to the catalyst. This step is associated with an activation energy; however, it is significantly lower than that for the uncatalyzed reaction. Finally, the product P seperates from the catalyst in an endothermic step. The energy diagram illustrates 4 ways the catalyst works : The catalyst offers an alternative path for the reaction that is energetically more favorable The activation energy of the catalytic reaction is significantly smaller than that of the uncatalyzed reaction; hence the rate of the catalytic reaction is much larger The overall change in free energy for the catalytic reaction equals that of the uncatalyzed reaction. Hence, the catalyst does not affect the equilibrium constant for the overall reaction. A catalyst cannot change the thermodynamics of a reaction but it can change the kinetics. The catalyst accelerates both the forward and the reverse reaction to the same extent. In other words, if a catalyst accelerates the formation of product P from A and B, it will do the same for the decomposition of P into A and B.
