Unit 8: Chemical
Reactions
Net Ionic Equations
Recall, aqueous (aq)
means a substance that is
dissolved in water.
When ionic solids dissolve, their ions that
make up the formula dissociate, or
separate. Each ion is then surrounded by
water molecules.
• Ionic compounds that dissociate will
conduct electricity (called an
electrolyte).
• Non-electrolytes: are solutions that do
not conduct electricity (do not ionize –
example: sucrose).
Precipitation Reactions
• Produce a water-insoluble product
(precipitate)
• Their reactants are usually watersoluble
• If a cation and anion can come together
to form an insoluble substance, a
precipitate forms.
To determine if a precipitate forms, a
solubility chart is used.
Predict the solubilities of the
following compounds:
1.
2.
3.
4.
KCl
Mg(CO3)
Fe2O3
Cu(NO3)2
Soluble
Insoluble
Insoluble
Soluble
Steps for Writing Net Ionic Equations
1. Write the balanced formula equation.
2. Use the solubility chart to determine soluble and
insoluble substances.
3. For any aqueous substances (soluble), split the
compound into its ions and separate each with a
plus sign. The subscripts of the ions become
coefficients, and multiply the subscript and
balanced equation coefficient if need be.
4. Cancel any spectator ions (ions that appear on
either side of the equation – do not participate in
the reaction).
5. Rewrite the equation including the proper state of
matter symbols and omitting the spectator ions.
Let’s try some
examples! 
Write the balanced net ionic equation for the
reaction of aqueous BaCl2 and Na2(SO4) to give
Ba(SO4) and NaCl.
Balanced Molecular Equation:
BaCl2 (aq) + Na2(SO4) (aq)  Ba(SO4)(s) + 2NaCl(aq)
Overall Ionic Equation: CROSS-OUT SPECTATOR IONS!
Ba+2 + 2Cl-1 + 2Na+1 + (SO4)-2  Ba(SO4)(s)+ 2Na+1 + 2Cl-1
Net Ionic Equation:
Ba+2(aq) + (SO4)-2(aq)  Ba(SO4)(s)
Write the balanced net ionic equation for
the reaction of solid lead (II) hydroxide and
hydrochloric acid.
Balanced Molecular Equation:
Pb(OH)2 (s) + 2HCl(aq)  PbCl2(s) + 2H2O(l)
CROSS-OUT SPECTATOR IONS!
Overall Ionic Equation: Wait…there aren’t any!
Pb(OH)2(s) + 2Cl-1 + 2H+1  PbCl2(s)+ 2H2O(l)
Net Ionic Equation:
Pb(OH)2(s) + 2H+1(aq) + 2Cl-1(aq) PbCl2(s)+2H2O(l)
Summary of Important Points:
• Ionic compounds are the only substances that
have the potential to dissociate in solution,
they should be labeled with the symbol (aq).
• Any substance other than a water-soluble
substance WILL NOT break up into ions and
will therefore be labeled with the symbols:
(s), (l), or (g).
• For our purposes acids are always considered
to be aqueous.