Double Replacement Reactions

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Double Replacement Reactions

• How do we know if these happen?

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Double Replacement Reaction

• 2 KI(aq) Pb(NO3)2(aq) ? 2 KNO3(aq) PbI2(s)

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Double Replacement Reactions

• Two types of Double Replacement Reactions
• Formation of an insoluble precipitate
• NaCl(aq) AgNO3(aq) ? NaNO3(aq) AgCl(s)
• Formation of a gas
• Acid salt ? gas another salt
• H2SO4(aq) Na2S(aq) ? H2S(g) Na2SO4(aq)

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Solubility Rules

• All sodium, potassium, and ammonium salts are
  soluble
• All acetate, nitrate, and chlorate salts are
  soluble
• All halide salts (F, Cl, Br, I) are soluble
• Except lead (II), silver, and mercury (I)
• All sulfates are soluble
• Except calcium, barium, lead (II), and silver
• All carbonates, phosphates, and sulfides are
  INSOLUBLE
• Except sodium, potassium, ammonium

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Ionic Equations

• Since ionic compounds (salts) exist as ions in
  solution, a precipitation reaction can be shown
  as ions
• NaCl(aq) AgNO3(aq) ? NaNO3(aq) AgCl(s)
• Na(aq) Cl-(aq) Ag(aq) NO3-(aq) ? Na(aq)
  NO3-(aq) AgCl(s)
• This is the ionic equation for the reaction
• Be careful with coefficients and subscripts from
  balanced formula equations

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Net Ionic Equations

• Na(aq) Cl-(aq) Ag(aq) NO3-(aq) ? Na(aq)
  NO3-(aq) AgCl(s)
• Na and NO3- ions are on both side, so they can
  be cancelled
• Cl-(aq) Ag(aq) ? AgCl(s)
• Na and NO3- are spectator ions
• They are soluble on both sides of the ionic
  equation
• The net ionic equation shows the reaction without
  the spectator ions
• The net ionic equation shows which ions react and
  how the reaction occurs

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For the following sets of reactants

• Predict if a reaction will occur, based on
  solubility rules
• Write a balanced formula equation, if the
  reaction occurs
• Write a balanced ionic equation, if the reaction
  occurs
• Write a balanced net ionic equation, if the
  reaction occurs

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Double Replacement Reactions

1. Potassium chromate silver nitrate
2. Sodium hydroxide iron (III) chloride
3. Sodium nitrate calcium chloride
4. Lead (II) acetate potassium sulfate
5. Silver nitrate magnesium sulfate
6. Potassium hydroxide nitric acid
7. Sodium acetate potassium carbonate