Solutions and Equilibrium

Heterogeneous Equilibrium Reaction occurs in more than one phase K EQ = Products Reactants Solids and liquids are not included in the equilibrium constant expression for heterogeneous equilibrium FeO(s) + CO(g) ⇌ Fe(s) + CO 2 (g) K EQ = [CO 2 ] [CO]

The concentration of pure solid or liquid is not included in the equilibrium constant expression for heterogeneous equilibrium.

Solubility Product Constant The equilibrium constant for the solubility equilibrium of a slightly soluble ionic compound BaSO 4 (s)  Ba 2+ (aq) + SO 4 2- (aq) Ksp = [Ba 2+ ] [SO 4 2- ] PbI 2  Pb 2+ (aq) + 2I - (aq) Ksp = [Pb 2+ ] [I - ] 2

Solubility Product Constant ** If Ksp is small = low solubility BaSO 4 Ksp = 1.1 X CaSO 4 Ksp = 2.4 X Fe(OH) 2 Ksp = 7.9 X Which is most soluble? CaSO 4 Which is least soluble? Fe(OH) 2

Common Ion Effect When a common ion reduces the solubility of a salt

What is the common ion? Cl - Which direction is equilibrium driven? Left – forming more undissolved NaCl

Learning Check If KBr is added to a solution containing PbBr 2(aq), will more PbBr 2 solidify? Yes If KBr is added to a solution containing NaCl, will more NaCl precipitate? No, no common ion

Reactions that go to Completion K EQ is large A gas leaves the system 2KClO 3 (s)  2KCl(s) + 3O 2 (g) Water is formed HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 O(l) A precipitate is made (Table F) AgNO 3 (aq) + NaCl(aq)  NaNO 3 (aq) + AgCl(s)