Question

Use the PhET Reactions & Rates interactive simulation to simulate a system. On the “Single collision” tab of the simulation applet, enable the “Energy view” by clicking the “+” icon. Select the first A + BC⟶AB + C reaction (A is yellow, B is purple, and C is navy blue). Using the “straight shot” default option, try launching the A atom with varying amounts of energy. What changes when the Total Energy line at launch is below the transition state of the Potential Energy line? Why? What happens when it is above the transition state? Why?

Short answer

When the total energy line is below the transition state of the potential line, the reaction does not occur. Above the transition potential energy line, the reaction proceeds in the forward direction.

Step-by-step solution

Energy of Activation

For any single step chemical reaction, the peak of the transition state energy represents the Energy of Activation, E_afor the given reaction. For the forward reaction to occur, the reactants must have total energy \({\bf{E}}\left( {\bf{T}} \right) \ge {{\bf{E}}_{\bf{a}}}\).

Total energy less than transition state energy

Initially, when the total energy line is below the transition state potential energy the reactants have total energy less than the activation energy, and the reaction \({\bf{A + BC}} \to {\bf{AB + C}}\) does not occur.

Total energy greater than transition state energy

Above the transition potential energy line, the reactants have energy greater than the activation energy, so the reaction proceeds in the forward direction.