Chemical Equilibrium

Irreversible reactions proceed in one direction

Irreversible reactions proceed in one direction only (A + B → C + D), while reversible reactions can proceed in both directions (A + B ⇌ C + D). Examp

At equilibrium

At equilibrium, forward and reverse reaction rates are equal, resulting in constant concentrations of all species. The system appears static but react

For reaction aA + bB ⇌

For reaction aA + bB ⇌ cC + dD, the equilibrium constant Kc = [C]ᶜ[D]ᵈ/[A]ᵃ[B]ᵇ. This ratio remains constant at a given temperature. For gases, Kp use

Homogeneous equilibrium involves all species

Homogeneous equilibrium involves all species in same phase (H₂(g) + I₂(g) ⇌ 2HI(g)). Heterogeneous equilibrium involves multiple phases (CaCO₃(s) ⇌ Ca

Reaction quotient Q has same form

Reaction quotient Q has same form as K but uses any concentrations, not just equilibrium ones. If Q < K: forward reaction favored; Q = K: at equilibri