AP Chemistry · Chapter 7 of 9

Equilibrium

Use equilibrium constants and reaction quotients to predict direction of change and final composition in reversible systems.

Why this chapter matters

Most real chemical systems are dynamic, and equilibrium tools let you predict how they respond to disturbances.

What you will learn

  • Write K expressions from balanced equations and interpret magnitude of K.
  • Use Q versus K to determine reaction shift direction.
  • Apply Le Chatelier reasoning to concentration, pressure, and temperature changes.

Lessons in this chapter

  1. Dynamic equilibrium modelDistinguish static appearance from equal forward and reverse rates.
  2. Equilibrium expressionsConstruct Kc or Kp correctly from stoichiometric coefficients.
  3. Q versus K reasoningPredict spontaneous shift direction before equilibrium is reached.
  4. Le Chatelier applicationsPredict and justify shifts due to external changes.

Study task

Build an ICE-table workflow for two reversible reactions and include a short written justification for each predicted shift after a disturbance.

Chapter checkpoint

For N2(g) + 3H2(g) <-> 2NH3(g), what is Kc?

Kc = [NH3]^2 / ([N2][H2]^3).