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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)
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Heterogeneous Equilibrium • Reaction occurs in more than one phase • KEQ = Products Reactants • Solids and liquids are not included in the equilibrium constant expression for heterogeneous equilibrium FeO(s) + CO(g) ⇌Fe(s) + CO2(g) KEQ = [CO2] [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 BaSO4(s) Ba2+(aq) + SO42-(aq) Ksp = [Ba2+] [SO42- ] PbI2 Pb2+(aq) + 2I-(aq) Ksp = [Pb2+] [I-]2
Solubility Product Constant ** If Ksp is small = low solubility BaSO4Ksp = 1.1 X 10-10 CaSO4Ksp = 2.4 X 10-5 Fe(OH)2Ksp = 7.9 X 10-16 Which is most soluble? CaSO4 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 undissolvedNaCl
Learning Check • If KBr is added to a solution containing PbBr2(aq), will more PbBr2 solidify? • Yes • If KBr is added to a solution containing NaCl, will more NaCl precipitate? • No, no common ion
Reactions that go to Completion • KEQ is large • A gas leaves the system 2KClO3(s) 2KCl(s) + 3O2(g) • Water is formed HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) • A precipitate is made (Table F) AgNO3(aq) + NaCl(aq) NaNO3(aq) + AgCl(s)