AP Chemistry Unit 7: Equilibrium

Introduction

• Presenter: Jeremy Krug
• Focus: A review of Equilibrium in AP Chemistry.
• Resources: Full-length videos, study guides, and practice questions are available at UltimateReviewPacket.com.

Equilibrium Basics

• Definition: Refers to reversible processes where the rate of the forward reaction equals the rate of the reverse reaction.
• Indicators: Concentrations remain constant but not necessarily equal.
• Direction of Equilibrium:
  • Forward reaction is faster: More products.
  • Reverse reaction is faster: More reactants.

Equilibrium Constant

• Expression:
  • For concentration: ( K_c = \frac{[products]}{[reactants]} )
  • For pressure: ( K_p = \frac{P_{products}}{P_{reactants}} )
  • Solids and pure liquids are excluded.
• Reaction Quotient (Q): Similar to K but not at equilibrium.
• Temperature Dependence: Only temperature changes can alter the equilibrium constant.

Magnitude of Equilibrium Constant

• Large K: Favors products, equilibrium lies to the right.
• Small K: Favors reactants, equilibrium lies to the left.

Manipulating Equilibrium Constants

• Reaction Flip: The K value becomes reciprocal.
• Doubling Coefficients: K becomes squared.
• Adding Reactions: Multiply individual K values.

Calculating Equilibrium Concentrations

• ICE Chart: Initial, Change, Equilibrium
• Example: Use algebra to solve for unknowns and plug values into K expression.

Particle Diagrams

• Usage: Visual representation of reactants and products.
• Estimating Partial Pressure: Use mole fraction and total pressure.

Le Chatelier’s Principle

• System Disturbance: System readjusts to reach equilibrium.
  • Adding substances shifts equilibrium to the opposite side.
  • Removing substances causes the same side to increase.
  • Volume changes affect the side with more or fewer moles of gas.

Temperature Effects

• Exothermic: Adding heat shifts to reactants, reducing temperature shifts to products.
• Endothermic: Opposite effects.

Reaction Quotient (Q)

• Direction of Reaction:
  • ( Q > K ): Shifts left, making more reactants.
  • ( Q < K ): Shifts right, making more products.

Solubility and Ksp

• Example: Lead(II) bromide
  • Dissolution Calculation: Use ICE box.
  • Common Ion Effect: Presence of common ions reduces solubility.

Conclusion

• Further Resources: Check out more reviews and practice materials from Jeremy Krug.
• Next Review: Unit 8, focusing on Acids and Bases.