Equilibrium Constant (Kc)
Ratio of product to reactant concentrations at equilibrium, each raised to stoichiometric powers.
Example: For N2+3H2<=>2NH3: Kc=[NH3]^2/([N2][H2]^3).
Adaptive
Learn Chemical Equilibrium
Read the notes, then try the practice. It adapts as you go.When you're ready.
Session Length
~17 min
Adaptive Checks
15 questions
Transfer Probes
8
Lesson Notes
Chemical equilibrium occurs when forward and reverse reaction rates are equal, yielding constant concentrations. The equilibrium constant K quantifies the ratio of product to reactant concentrations at equilibrium.
Le Chatelier principle predicts how systems respond to disturbances. ICE tables systematically calculate equilibrium concentrations. Q compared to K determines reaction direction. Ksp governs solubility equilibria and the common ion effect.
Covers Kc, Kp, ICE tables, Le Chatelier principle, Q vs K, Ksp, and common ion effect for AP Chemistry Unit 7.
You'll be able to:
- Write equilibrium expressions (Kc, Kp) and calculate equilibrium constants
- Use ICE tables to determine equilibrium concentrations
- Apply Le Chatelier principle to predict shifts in equilibrium
- Compare Q and K to predict reaction direction
- Calculate solubility from Ksp and apply the common ion effect
One step at a time.
Interactive Exploration
Adjust the controls and watch the concepts respond in real time.
Key Concepts
Kp
Equilibrium constant in partial pressures: Kp=Kc(RT)^(delta-n).
Example: For 2SO2+O2<=>2SO3, delta-n=-1.
Le Chatelier Principle
A system at equilibrium shifts to counteract a disturbance.
Example: Adding N2 shifts toward NH3.
ICE Table
Initial-Change-Equilibrium table for calculating equilibrium concentrations.
Example: Start 1.0M, change -x, equilibrium 1.0-x.
Reaction Quotient (Q)
Same form as K using current concentrations. Q<K: forward; Q>K: reverse.
Example: Q=0.5, K=10: goes forward.
Ksp
Equilibrium constant for sparingly soluble salt dissolving.
Example: AgCl: Ksp=[Ag+][Cl-]=1.8e-10.
Common Ion Effect
Adding an ion already present decreases solubility.
Example: NaCl added to saturated AgCl decreases solubility.
Heterogeneous Equilibrium
Pure solids and liquids are omitted from K expressions.
Example: CaCO3(s)<=>CaO(s)+CO2(g): K=P(CO2).
Explore your way
Choose a different way to engage with this topic — no grading, just richer thinking.
Explore your way — choose one:
Concept Map
See how the key ideas connect. Nodes color in as you practice.
Worked Example
Walk through a solved problem step-by-step. Try predicting each step before revealing it.
Adaptive Practice
This is guided practice, not just a quiz. Hints and pacing adjust in real time.
Small steps add up.
What you get while practicing:
- Math Lens cues for what to look for and what to ignore.
- Progressive hints (direction, rule, then apply).
- Targeted feedback when a common misconception appears.
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