53 Days Until the Harvard Westlake FinalCatalyst:1. Define what equilibrium is using the rate of the

forward reaction and the rate of the reverse reaction.

2. What is activation energy? Label it on a reactioncoordinate.

3. How is a catalyst related toactivation energy?

End

The Briggs-Rauscher Reaction

IO3− + 2H2O2 + CH2(COOH)2 + H+ ICH(COOH)⇌ 2 + 2O2 + 3H2O

Amber Color Navy Blue Color

Justify – TPS

• Why did the reaction keep changing colors?

LECTURE 8.4 – LE CHATELIER’S PRINCIPLE

Today’s Learning Target

• LT 8.7 – I can define Le Chatelier’s principle and use this principle to predict how concentration, temperature, and pressure will impact a given equilibrium.

What is Le Chatelier’s Principle?

Le Chatelier’s Principle • “If a system at equilibrium

is disturbed by a change in temperature, pressure, or concentration, the system will shift its equilibrium position so as to counteract the effect of the stress.”

• If equilibriums are disturbed, it will shift to restore that equilibrium.

How do concentration, pressure, and temperature impact equilibrium?

Le Chatelier’s Principle and Concentration

• If we add more of a product/reactant, then our reaction will shift to the other side in order to compensate for this new amount.

Class Example

• I have the following equilibrium:H2O H⇌ 3O+ + OH-

• If I add H3O+, then will my reaction shift to the right or to the left?

Table Talk• I have the following equilibrium:

CaCO3 CaO + CO⇌ 2

• If I add CaCO3, then will my reaction shift to the right or to the left?

Le Chatelier’s Principle and Volume/Pressure

• If we increase pressure, the reaction shifts to the side with less molecules

• If we decrease pressure, the reaction shifts to the side with more molecules

Class Example

• I have the following equilibrium:N2 (g) + 3H2 (g) 2NH⇌ 3 (g)

• If I increase the pressure, then will my reaction shift to the right or to the left?

Table Talk• I have the following equilibrium:

CaCO3 CaO + CO⇌ 2

• If I decrease pressure, then will my reaction shift to the right or to the left?

Le Chatelier’s Principle and Temperature• When a reaction is endothermic, heat is listed as a

reactant.Heat + Reactants Products

• When a reaction is exothermic, heat is listed as a product.

Reactants Products + Heat• Therefore, treat heat like a reactant or a product

Class Example

• I have the following equilibrium:N2 (g) + 3H2 (g) 2NH⇌ 3 (g) + 92 kJ

• If I increase the temperature, then will my reaction shift to the right or to the left?

Table Talk• I have the following equilibrium:

556 kJ + CaCO3 (s) CaO (s) + CO⇌ 2 (g)

• If I decrease the temperature, then will my reaction shift to the right or to the left?

Summarize

Use the following words:• Le Chatelier• Concentration• Pressure• Temperature • Stress

White Board Questions• State whether it will shift to the left, right, or stay the

same based on the given conditionsNaOH (aq) + HCl (aq) NaCl (s) + H2O (l)

(1)Add HCl(2)Remove NaOH(3)Add NaCl(4)React NaOH with HNO3

White Board Questions• State whether it will shift to the left, right, or stay the

same based on the given conditions4HCl (g) + O2 (g) 2H2O (g) + 2Cl2 (g) + 113 kJ • Increase pressure • Decrease temperature• Add H2O

• Remove O2

• Add HCl

White Board Questions• State whether it will shift to the left, right, or stay the

same based on the given conditionsNaCl (aq) Na+ (aq) + Cl- (aq) + 426 kJ

(1)Decrease the temperature (2)Add Na+

(3)Remove Cl-

(4)Add HCl (think about what the compound contains)

Screencast-o-matic• Today, students get to the be the teacher!• You will have an opportunity to teach the world

how Le Chatelier’s Principle works by using screencast-o-matic to solve problems involving Le Chatelier’s Principle and record them.

• Wikispaces!• Screencast-o-matic!• ACS Chemistry Olympiad!• Unit 8 Exam!

Closing Time