Non-redox Reactions/ Double Replacement Reactions

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Non-redox Reactions/Double Replacement Reactions

• OBJECTIVES
• Distinguish between a non-redox and a redox
  reaction.
• Recognize a double replacement (D.R.) reaction.
• Predict the products of a D.R. reaction.
• Predict whether a D.R. reaction will occur using
  solubility rules or formation of gas or H2O(l)
  (neutralization reaction).
• Complete and balance any D.R. that will occur.
• Write complete ionic and net ionic reactions.

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Non-redox Reaction

• The oxidation number (charge) of the ions
  involved does not change from the reactant to the
  product side.
• Na2SO4(aq) CaCl2(aq) CaSO4(s) 2NaCl(aq)
• Redox (the oxidation s are changing)
• 2 Fe 3 Cl2 ? 2 FeCl3
• 2 K(s) FeCl2(aq) ? Fe(s) 2 KCl(aq)

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Double Replacement

• Two things replace each other.
• Reactants must be two ionic compounds or acids.
• Usually in aqueous solution
• Na2SO4(aq) CaCl2(aq)
• The positive ions change place.
• Na2SO4(aq) CaCl2(aq)Ca2 SO42- Na1Cl-1
• Na2SO4(aq) CaCl2(aq) CaSO4(s) 2NaCl(aq)

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To Double Replaceor Not to Double Replace?That
is the Question?

• Will only happen if one of the products
• doesnt dissolve in water and forms an insoluble
  solid (s), precipitate (ppt).
• or is a gas that bubbles out.
• or water forms, H2O(neutralization reaction)
  feel for heat.

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Predicting the Precipitate

• Insoluble salt a precipitate/solid (s)
• Solubility rules (see handout for explanation)
• CASH N GiAm

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Solubility Rules PracticePredict whether each of
the following will be soluble (aq) or an
insoluble ppt (s)

• KCl
• Na2SO4
• CaSO4
• AgSO4
• Na2CO3
• MgS

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Solubility Rules Practice

• KCl(aq)
• Na2SO4(aq)
• CaSO4(s)
• AgSO4(s)
• Na2CO3(aq)
• MgS(s)

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Double Replacement

• Two elements in reactants take the place of
  each other
• AB CD ? AD CB
• AgNO3(aq) NaCl(aq)? AgCl(s) NaNO3(aq)
• Zn(OH)2(aq) 2HCl(aq) ? ZnCl2(aq) 2H2O(l)

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Double Replacement

• Will only happen if one of the products
• doesnt dissolve in water and forms an insoluble
  solid (s), precipitate (ppt).
• or is a gas that bubbles out.
• or water forms, H2O (neutralization reaction)
  feel for heat.

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Learning Check

• Which of the following reactions is double
  replacement?
• A. 2Al(s) 3H2SO4(aq) ? Al2(SO4)3(aq)
  3H2(g)
• B. Na2SO4(aq) 2AgNO3(aq)?Ag2SO4(s) 2NaNO3(aq)
• C. 3C(s) Fe2O3(s) ? 2Fe(g) 3CO(g)

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Complete Net Ionic Equations

• Many reactions occur in water- that is, in
  aqueous solution
• Many ionic compounds dissociate, or separate,
  into cations and anions when dissolved in water
• Now we can write a complete ionic equation Net
  ionic equation.

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Complete Ionic Equation

• Example
• AgNO3(aq) NaCl (aq) ? AgCl (s) NaNO3(aq)
• this is the full equation (molecular equation)
• 2. now write it as an complete ionic equation
• Anything (aq) will dissociate (separate into
  ions)
• Ag NO3- Na Cl- ? AgCl(s) Na NO3-

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Net Ionic Equation

• Complete ionic equation
• Ag NO3- Na Cl- ? AgCl(s) Na NO3-
• 3. can be simplified by eliminating ions not
  directly involved in making the reaction happen
  (spectator ions) net ionic equation
• Ag Cl- ? AgCl(s)
• Na and NO3- are spectator ions and are removed
  in the net ionic equation.