Transcript Net Ionic Equations

Net Ionic Equations
Net Ionic Equations…

…describe a chemical reaction in
solution recognizing the role of
dissociation.
3 steps
Non Ionic equation (aka balanced
chemical equation)
 Total ionic equation
 Net ionic equation
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Example
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Solutions of lead (II) nitrate and
potassium iodide are mixed.
Non ionic equation
Pb(NO3)2 (aq) + 2KI (aq) ---> PbI2(s) + 2KNO3 (aq)
Total ionic equation
Dissociate or ionize everything that is:
 Aqueous and ionic
 Aqueous and acid
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Total ionic
Pb(NO3)2 (aq) + 2KI (aq)---> PbI2(s) + 2KNO3 (aq)
Dissociate
Pb2+(aq) + 2NO3¯(aq) + 2K+(aq) + 2I¯(aq) --->
PbI2(s) + 2K+(aq) + 2NO3¯(aq)
NOT aqueous so not dissociated
Spectator species (entities)
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A spectator species is a species (entity)
that does not change in the reaction,
is not involved in the reaction.
Cancel spectator species
Total ionic equation:
Pb2+(aq) + 2NO3¯(aq) + 2K+(aq) + 2I¯(aq) --->
PbI2(s) + 2K+(aq) + 2NO3¯(aq)
What remains is the net ionic equation.
Net ionic equation
Pb2+(aq) + 2I¯(aq) ---> PbI2(s)
Example
Chlorine gas is bubbled through a solution of
sodium fluoride.
Non ionic equation:
Cl2(g) + 2NaF(aq) ---> F2(g) + 2NaCl(aq)
Total ionic equation
Dissociate everything that is:
Aqueous and ionic or aqueous and acid
Cl2(g) + 2NaF(aq) ---> F2(g) + 2NaCl(aq)
Cl2(g) + 2Na+(aq) + 2F¯(aq) --->
F2(g) + 2Na+(aq) + 2Cl¯(aq)
Net Ionic Equation
Cancel all spectator species:
Cl2(g) + 2Na+(aq) + 2F¯(aq) --->
F2(g) + 2Na+(aq) + 2Cl¯(aq)
What remains is the net ionic equation:
Cl2(g) + 2F¯(aq) ---> F2(g) + 2Cl¯(aq)
Watch for:
Occasionally there are no spectator
species. Then the total and the net are
the same.
 Occasionally all species in the total ionic
equation are spectators, everything
cancels. What does this mean??
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