Potential Energy and Kinetics Truman Chemistry Department

How is potential energy related to kinetics? The difference in PE can determine the amount of energy needed to start a reaction, or amount of energy transferred in a reaction.

What can a potential energy diagram tell us about a reaction?

What is the reaction coordinate? Describes progress or time of reaction Only as quick as the slowest step Ex. Step 1 ABC=> A + B + C (Slow Step) Ea High Step 2 C + D=> CD (Fast Step) Ea Low

What is DH? ΔH = energy used in bond breaking reactions - energy released in bond making products Bonds Broken= Energy Released Bonds Formed= Energy Consumed

DH examples CH4 + 2O2 => CO2 + 2H2O C--H = 413 O=O = 498 C=O = 500 O--H = 398 On which side is energy released? On which side is it absorbed What is the difference in energy? Is DH positive or negative?

What is the activated complex? Structure formed when particles collide. Old bonds breaking and new bonds forming Often required the addition of energy

Different types of PE diagrams:

What’s the difference? Exothermic Endothermic PE decrease KE increases DH is negative Products more stable Reactants less stable Endothermic PE increases KE decreases DH is positive Products less stable Reactants more stable

Now you try (Label this):

Questions Assessment http://www.chemcool.com/regents/kineticsequilibrium/aim4.htm