Equilibrium Flashcards
(28 cards)
What is chemical equilibrium?
A dynamic and reversible process where the forward and reverse reaction rates are equal.
What conditions are required for equilibrium?
A closed system with constant temperature and pressure.
What happens to concentrations at equilibrium?
They remain constant but are not necessarily equal.
Why can a system at equilibrium not perform work?
Because ΔG = 0, meaning no net energy change occurs.
What does it mean for a reaction to be reversible?
Both forward and reverse reactions occur.
Give an example of an effectively irreversible reaction.
Combustion or precipitation (e.g., BaSO₄ ↓).
Why are some reactions incomplete?
They reach equilibrium with significant amounts of both reactants and products.
Does equilibrium mean the reaction stops?
No, it means the rates are equal; the system is dynamic.
How do you write the rate expressions at equilibrium?
Forward: kₓ[reactants], Reverse: kₛ[products].
Define the equilibrium constant Kc.
Kc = [products]ⁿ / [reactants]ⁿ using equilibrium concentrations.
How is Kp defined?
Kp = (p(products))ⁿ / (p(reactants))ⁿ using partial pressures.
What does K ≫ 1 mean?
Products are favoured at equilibrium.
What does K ≪ 1 mean?
Reactants are favoured at equilibrium.
What does K ≈ 1 mean?
Significant amounts of both products and reactants are present.
What is the reaction quotient Q?
A value calculated like K, but not necessarily at equilibrium.
What does Q < K mean?
The forward reaction is favoured.
What does Q > K mean?
The reverse reaction is favoured.
What does Q = K mean?
The system is at equilibrium.
What is the relationship between ΔG and spontaneity?
ΔG < 0 = spontaneous, ΔG = 0 = equilibrium, ΔG > 0 = non-spontaneous.
What is the equation linking ΔG and Q?
ΔG = ΔG⁰ + RT lnQ.
How does pressure affect ΔG in gases?
ΔG = nRT ln(P₂/P₁).
What is the general formula for G vs pressure?
G = G⁰ + nRT ln(P).
How does entropy (S) influence ΔG?
Higher entropy favours lower ΔG (more spontaneous).
Why is K affected by stoichiometry?
K is derived from the balanced chemical equation.
