quantifying equilibria

equilibrium constant K

when are reactants and products favoured

reactants when K < 1, products when K > 1

K_p

equilibrium constant expressed as partial pressures. only used for reactions taking place completely in the gas phase

reaction quotient Q

relation to K

the relative amounts of products and reactants at any point during a reaction

Q = K at equilibrium

Q > K, reaction proceeds to left

Q < K reaction proceeds to right

non-equilibrium gibbs energy

gibbs energy at equilibrium

Q = K and ΔG = 0 so ΔG^⦵ = -RTlnK

as ΔG = ΔH - TΔS, ΔH - TΔS = -RTlnK

what is solubility

the amount of substance (mol) that can be dissolved in a given amount of substance (dm³)

chemical equation for dissolving

MX (s) ⇌ M⁺ (aq) + X^- (aq)

solubility product

Ksp = [M⁺ (aq)][X^- (aq)]

large Ksp = high solubility

concentration and activity of solids

both 1