Solutions and Equilibrium

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Solutions and Equilibrium
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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

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

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Solubility Product Constant

If Ksp is small low solubility BaSO4 Ksp
1.1 X 10-10 CaSO4 Ksp 2.4 X 10-5 Fe(OH)2 Ksp
7.9 X 10-16 Which is most soluble? CaSO4 Which
is least soluble? Fe(OH)2
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Common Ion Effect

• When a common ion reduces the solubility of a salt

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

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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)