Equilibrium, Kinetics, HomeostasisEquilibrium, Kinetics, Homeostasis

Dr. Ron RusayDr. Ron Rusay

Spring 2004Spring 2004

© Copyright 2004 R.J. Rusay© Copyright 2004 R.J. Rusay

Dynamic EquilibriumDynamic Equilibrium““The Pennies”The Pennies”

• Organize into groups of 3-4.Organize into groups of 3-4.• Dr. R will assign your group a number.Dr. R will assign your group a number.• In your group, select one person as:In your group, select one person as:

1) Money Keeper1) Money Keeper2) Recorder2) Recorder3) Transfer Agent (Calculating agent)3) Transfer Agent (Calculating agent)4) Auditor (Can be combined with #3)4) Auditor (Can be combined with #3)

• Send the Recorder to see Dr. R. for your accounting form.Send the Recorder to see Dr. R. for your accounting form. Be sure to record other group member names on the form.Be sure to record other group member names on the form.• After recording all of the names send the Money Keeper After recording all of the names send the Money Keeper to see Dr. R. for your capital stake.to see Dr. R. for your capital stake.• Await instructions for phase I.Await instructions for phase I.

Dynamic EquilibriumDynamic Equilibrium““The Pennies”The Pennies”

Phase I:Phase I:

Phase II:Phase II:

There will be 8 phases. You can begin and go through them at your own pace. There will be 8 phases. You can begin and go through them at your own pace.

Give Dr. R. the accounting form when completed.Give Dr. R. the accounting form when completed.

Dynamic EquilibriumDynamic Equilibrium““The Pennies”The Pennies”

Class Resultshttp://ep.llnl.gov/msds/chem120/equil-graph.html

Simulator:http://mc2.CChem.Berkeley.EDU/Java/equilibrium/

Dynamic EquilibriumDynamic Equilibrium““The Pennies”The Pennies”

http://ep.llnl.gov/msds/chem120/equil-graph.html

Chemical EquilibriumChemical Equilibrium

Reaction Diagram of OReaction Diagram of O33 decomposing decomposing

O3 (g) + O(g) 2 O2 (g) [breakdown (decomposing)]

O2 (g) + O(g) O3 (g) [formation]

Chemical EquilibriumChemical Equilibrium

Most of the reactions considered until now Most of the reactions considered until now have had reactants react completely to form have had reactants react completely to form products. These reactions “went” only in one products. These reactions “went” only in one direction. [direction. []] Some reactions can react in either direction. Some reactions can react in either direction. They are “They are “reversible”reversible”. [ ]When this occurs . [ ]When this occurs some amount of reactant(s) will always some amount of reactant(s) will always remain at the end of change. Ozone and remain at the end of change. Ozone and oxygen in the atmosphere follow this type.oxygen in the atmosphere follow this type.

Chemical EquilibriumChemical Equilibrium(Definitions)(Definitions)

A chemical system where the A chemical system where the concentrations of reactants and concentrations of reactants and products remain products remain constantconstant over time. over time. On the On the molecular levelmolecular level, the system is , the system is dynamic: dynamic: The rate of change is the The rate of change is the same in both the forward and reverse same in both the forward and reverse directions.directions.

Equilibrium ExpressionEquilibrium Expression

For any equilibriumFor any equilibrium Reactants Reactants ProductsProducts

The Equilibrium Expression relates the concentrations of The Equilibrium Expression relates the concentrations of products and reactants. products and reactants.

The Equilibrium constant, The Equilibrium constant, KK,, indicates which is favored. indicates which is favored. If If KK is large the products are favored, and if is large the products are favored, and if KK is small is small

reactants are favored.reactants are favored.

K =K =Reactants

Products ______________________

For a reaction:For a reaction:

• j j A + A + k k B B l l C + C + m m DD The law of mass action is represented The law of mass action is represented

by the Equilibrium Expression: where K by the Equilibrium Expression: where K is the Equilibrium Constant. (Units for K is the Equilibrium Constant. (Units for K will vary.)will vary.)Klmjk=CDABLaw of Mass ActionLaw of Mass Action

((TheThe Equilibrium Expression)Equilibrium Expression)

Equilibrium ExpressionsEquilibrium Expressions

If a reaction is reversed where reactants If a reaction is reversed where reactants become products and the old products become products and the old products become reactants, the new Equilibrium become reactants, the new Equilibrium Expression becomes the reciprocal of Expression becomes the reciprocal of the old. the old.

KKnewnew = 1/K = 1/Koldold

Le Châtelier’s PrincipleLe Châtelier’s Principle

. . . If change is imposed on a system . . . If change is imposed on a system at equilibrium, the system will shift in a at equilibrium, the system will shift in a direction that tends to reduce that direction that tends to reduce that change and re-establish the original change and re-establish the original equilibrium’s relationship of reactants equilibrium’s relationship of reactants products.products.

Changes on the SystemChanges on the System

ConcentrationConcentration: The system will shift : The system will shift concentrations concentrations awayaway from the added from the added component. component. KK remains the same remains the same..

Changes on the System Changes on the System (continued)(continued)

The Effect of CatalystsThe Effect of Catalysts A catalyst lowers the activation energy A catalyst lowers the activation energy

barrier for any reaction….effects both barrier for any reaction….effects both forward and reverse directions!forward and reverse directions!

A catalyst will decrease the time it takes A catalyst will decrease the time it takes to reach equilibrium.to reach equilibrium.

A catalyst A catalyst does notdoes not effect the effect the composition of the equilibrium mixture.composition of the equilibrium mixture.

Catalysts Lower the Energy of ActivationCatalysts Lower the Energy of Activation

OO33

OO22

with Freonwith Freon

HomeostasisHomeostasis Physiological EquilibriumPhysiological Equilibrium

http://physioweb.med.uvm.edu/homeostasis/

““Pools, Balance, Equilibrium, Bio-feedback”Pools, Balance, Equilibrium, Bio-feedback” Let Pool be a person’s body weight.Let Pool be a person’s body weight. Let Input and Output be energy. Let Input and Output be energy. (What are possible sources of energy input (What are possible sources of energy input

and forms of energy output?)and forms of energy output?) Let’s consider a 70 kg individual with Input = Let’s consider a 70 kg individual with Input =

Output = 2000 Cal / dayOutput = 2000 Cal / day