AP Chemistry Unit 7: Equilibrium Review

Introduction

• Presenter: Jeremy Krug
• Review of AP Chemistry Unit 7 focusing on Equilibrium
• Resources available: full-length videos, free-response walkthroughs, practice materials on UltimateReviewPacket.com

Equilibrium Concepts

• Definition: Equilibrium refers to reversible processes (e.g., boiling/condensing water, formation/dissolution of a precipitate).
• Chemical Equilibrium:
  • Occurs when the rate of the forward reaction equals the rate of the reverse reaction.
  • At equilibrium, concentrations of reactants and products remain constant.
  • Double-headed arrow used to indicate reversibility.

Reaction Rates and Equilibrium

• The direction of equilibrium depends on the relative rates of forward and reverse reactions.
  • Faster forward reaction: more products than reactants.
  • Faster reverse reaction: more reactants.

Equilibrium Constant (K)

• Kc: Ratio of product concentrations to reactant concentrations raised to the power of their coefficients.
• Kp: Similar to Kc but uses partial pressures.
• Solids and pure liquids are excluded from calculations.
• Reaction Quotient (Q): Calculated like K but with non-equilibrium concentrations.

Calculating Equilibrium Constants

• Use equilibrium concentrations in the expression to find K.
• Given K and some concentrations, solve for unknown concentrations.
• Temperature changes affect K; it is temperature dependent.

Magnitude of Equilibrium Constant

• Large K: Reaction favors products, equilibrium lies to the right.
• Small K: Reaction favors reactants, equilibrium lies to the left.
• Manipulating reactions affects K:
  • Flipping a reaction: K becomes reciprocal.
  • Doubling coefficients: K is squared.
  • Adding reactions: Multiply individual Ks.

ICE Box Method

• Organizes data: Initial, Change, Equilibrium concentrations.
• Useful for solving equilibrium problems.

Particle Diagrams

• Represent relative amounts of reactants and products.
• Large product presence indicates a large equilibrium constant.
• Partial pressure can be calculated using mole fraction and total pressure.

Le Châtelier's Principle

• Systems adjust to restore equilibrium when disturbed.
  • Adding/removing substances affects the reaction direction.
  • Volume changes affect gas moles direction.
  • Temperature changes affect reaction sides (exothermic vs. endothermic).

Reaction Quotient and Direction of Reaction

• Q compared to K determines the reaction direction:
  • Q > K: Reaction proceeds left (more reactants).
  • Q < K: Reaction proceeds right (more products).

Solubility and Ksp

• Ksp: Solubility product constant for ionic compounds.
• Calculate molar solubility with balanced equations.
• Common ion effect reduces compound solubility.
• Example: Lead(II) bromide in sodium bromide solution.

Conclusion

• Equilibrium summary provides a brief overview of key concepts.
• Encouragement to like the video and check out additional resources for AP exam preparation.
• Look forward to Unit 8 covering Acids and Bases.