AP Chemistry Flashcards: Introduction to Equilibrium
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 11 cards to help you master important concepts.
Are the concentrations of reactants and products necessarily equal at equilibrium?
No, the concentrations are rarely equal. Equilibrium only requires that the concentrations are constant because the forward and reverse reaction rates are equal.
Card 1 of 11
All Flashcards (11)
Are the concentrations of reactants and products necessarily equal at equilibrium?
No, the concentrations are rarely equal. Equilibrium only requires that the concentrations are constant because the forward and reverse reaction rates are equal.
If a reaction is at equilibrium, have the forward and reverse reactions stopped?
No, the reactions have not stopped. The forward and reverse processes continue to occur at equal rates, which is why there is no net change.
Provide two examples of reversible processes that can establish equilibrium.
Two examples are phase changes (e.g., evaporation and condensation in a sealed container) and the dissolution of a salt in a saturated solution.
What does it mean for equilibrium to be "dynamic"?
Equilibrium is dynamic because the forward and reverse processes continue to occur, but at equal rates, resulting in no net observable change in the system.
What happens to the concentrations of reactants and products once a system reaches equilibrium?
Once equilibrium is established, the concentrations or partial pressures of both the reactants and the products remain constant over time.
A sealed container holds a saturated salt solution with excess solid salt at the bottom. Why is this system considered to be at equilibrium?
This system is at equilibrium because the rate at which the solid salt dissolves into the solution is equal to the rate at which the dissolved salt crystallizes back into a solid.
How do experimental observations indicate that a reversible process has reached equilibrium?
Equilibrium is indicated by the cessation of all observable changes, such as color, pressure, or concentration, within a closed system.
What is the relationship between the rates of the forward and reverse reactions at equilibrium?
At equilibrium, the rate of the forward process is exactly equal to the rate of the reverse process.
How can a graph of concentration versus time illustrate the establishment of equilibrium?
Such a graph shows equilibrium has been established when the curves representing the concentrations of all reactants and products become horizontal, indicating they are no longer changing.
What is a reversible process?
A reversible process is a chemical or physical change, such as a phase change or salt dissolution, that can proceed in both the forward and reverse directions.
What is the state of chemical equilibrium?
Equilibrium is the state in a reversible process where no observable changes occur because reactants and products are present at constant concentrations or partial pressures.