Chemical Kinetics Diagrams of Energy Changes in Reactions

What happens to Energy During a Reaction? Exothermic vs Endothermic Does it increase or decrease uniformly? Potential Energy Diagram:

Potential Energy Diagram: Forward Reaction Potential Energy (KJ)  Reaction Coordinate  H 2 + I 2 2HI Refer to the next slide for the key.

Parts of a Potential Energy Diagram A.Potential Energy of the Reactants B.Potential Energy of the Products C.Activated Complex = D. Potential Energy of the Activated Complex E. Activation Energy (E A ) = F. Heat of Reaction (∆H) = Is this reaction exothermic or endothermic?

Potential Energy Diagram: Reverse Reaction Potential Energy (KJ)  Reaction Coordinate  H 2 + I 2 2HI Refer to the previous slide for the key.

Potential Energy Diagram: FWD: _______________ REV: _______________ Potential Energy (KJ)  Reaction Coordinate  Complete the PE diagram by drawing arrows to indicate the appropriate factors.

Effect of a Catalyst: Potential Energy (KJ)  Reaction Coordinate 

Things to Consider Is the forward reaction exothermic or endothermic? Reverse reaction? Is ∆H positive or negative for the forward reaction? Reverse reaction? What factors are the same in the forward and reverse reactions and what factors are different? How does a catalyst affect the forward and reverse reactions? On what factors does the catalyst have an effect and on what factors does it not have an effect?

A + B  C + 30 KJ E A = 20 KJ Potential Energy (KJ)  Reaction Coordinate 

Enthalpy = Energy There is a tendency in nature to change to a state of lower energy (enthalpy). _________________ reactions result in a lower state of energy for the products than the reactants. _________________ reactions require less activation energy and therefore occur more easily than _______________ reactions. For the reasons above, _________________ reactions are said to be ___________________. Table I: Heats of Reaction at Standard Pressure and Room Temp. + Δ H = _________________________________ - Δ H = _________________________________

Entropy = Disorder There is a tendency in nature to change to a state of greater disorder (higher entropy). It is expected that systems will go from a state of _____________ entropy to a state of _____________ entropy and not the other way around. Think of your bedroom, or book bag, or the desk in front of this class. In going from solid  liquid  gas, is entropy increasing or decreasing? In going from solid  aqueous, is entropy increasing or decreasing? In a chemical reaction, the side with the greatest number of particles has the ____________entropy.

Homework Potential Energy Diagrams: Orange Book: Pg , Q *Pg , Q 3, 6-12, *Pg. 123, Q 24, 38, 39 Enthalpy and Entropy: Orange Book: Pg , Q *Pg. 122, Q 14, 29, 30, 34 Equilibrium: Orange Book: Pg , Q 13, 17, 20, 25-28, 31-33, 35, 36, 40 *Must do. Other HW questions are optional.