Energy Diagrams: Drawing it Out

Why are we learning this? Energy diagrams show how a reaction works. Energy diagrams display The energy of reactants and products The energy needed for a reaction to occur The energy absorbed or released due to reaction

Energy Diagram Parts Potential Energy of the reactants Potential Energy of the products Activation Energy E – the amount of energy required to reach the transition state or activated complex from the reactant Transition State, T s (Activated Complex) – when bonds break and form and reactants become products Enthalpy,  H – science word for heat, Energy of products – energy of reactants

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts Potential Energy

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts Potential Energy

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts max Potential Energy high low

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts max Potential Energy high low Kinetic Energy

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts max Potential Energy high low Kinetic Energy high minlow

Potential and Kinetic Energy Changes during a Collision Endothermic ReactantsActivated ComplexProducts max Potential Energy high low Uphill- endothermic! Kinetic Energy high minlow

Putting Pieces Together Transition State, T s Energy Reaction Reactants Products Activation Energy of forward reaction, E F E F = T s - Reactants Enthalpy of forward reaction,  H F  H F = Products - Reactants

Putting Pieces Together Transition State, T s Energy Reaction Reactants Products Activation Energy of reverse reaction, E R E R = T s - Products Enthalpy of forward reaction,  H R  H R = Reactants - Products

Types of Energy Diagrams Endothermic – the reaction absorbs heat so  H is positive The reactants have less potential energy than the products A + B AB  H > 0 A B

Types of Energy Diagrams Exothermic – the reaction releases heat so  H is negative The reactants have more potential energy than the products A + B AB  H < 0 A B

Types of Energy Diagrams Catalysts lower the activation energy of a reaction by finding an alternate route. However, the change in heat, or enthalpy is the same. A + B AB  H < 0 Blue without Catalyst Green with Catalyst A B

Try it together Use the numbers to find: What is E F ? What is  H F ? What is  H R ? What is E R ?

Pick the slow and fast reaction Ea Slow Fast- low Ea