Reactions in Aqueous Solutions
Prentice-Hall Chapter 11.3
Dr. Yager
Objectives

Describe the information found in complete
and net ionic equations.

Predict the formation of a precipitate in a
double-replacement reaction.
Structures in limestone caverns are formed when
carbon dioxide converts calcium hydrogen carbonate
into calcium carbonate. The calcium carbonate
precipitates and forms dramatic stalactites and
stalagmites. You will learn to predict the formation of
precipitates and write equations to describe the
reactions that produce them.
Net Ionic Equations

Salts dissociate into cations and anions in water.

Chemical reactions taking place in water are
aqueous reactions.

Standard Equation

Complete Ionic Equation

Net Ionic Equation
Standard Equation
AgNO3(aq) + NaCl(aq)
AgCl(s) + NaNO3(aq)
Complete Ionic Equation
Ag+(aq)+NO3-(aq)+Na+(aq)+Cl-(aq)
AgCl(s)+Na+(aq)+NO3-(aq)
The ions crossed out in red
don’t participate
Spectator Ions
Ag+(aq)+NO3-(aq)+Na+(aq)+Cl-(aq)
AgCl(s)+Na+(aq)+NO3-(aq)
The ions crossed out are called spectator ions.
Ag+(aq) + Cl-(aq)
AgCl(s)
This is the net ionic equation and only shows
particles directly involved in the chemical change.

An ion that appears on both sides of an
equation and is not directly involved in the
reaction is called a spectator ion.

The net ionic equation is an equation for
a reaction in solution that shows only
those particles that are directly involved in
the chemical change. It is balanced with
respect to both mass and charge.
A Precipitate is Formed
Sodium ions and nitrate
ions are not changed
during the chemical
reaction of silver nitrate
and sodium chloride, so
the net ionic equation is:
3Ca2+(aq) + 6OH-(aq) + 6H+ (aq) + 2PO43-(aq)
Ca3(PO4)2(s) + 6H2O(l)
This is both the complete
and net ionic equation!
(no spectator ions!)
Predicting the Formation of a Precipitate

Precipitation can be predicted by the rules of
solubility of ionic compounds.

Solubility: How much solid will dissolve in a
solution.

When two ionic compounds are mixed, the
cations can change partners.

If the partners are insoluble, then they
precipitate out of solution.
Remember these
ions
CO32-
Carbonate
PO43-
Phosphate
CrO42- Chromate
S2-
Sulfide
OH-
Hydroxide
Will a Precipitate Form?
Sodium nitrate is soluble but carbonate is
insoluble. The net ionic equation is
Will a Precipitate Form?
Al2(SO4)3 + NH4OH
?
CaCl2 + K2SO4
?
Will a Precipitate Form?
Al2(SO4)3 + NH4OH
Al(OH)3(s) Yes
Remember these
ions
CO32-
Carbonate
PO43-
Phosphate
CrO42- Chromate
S2-
Sulfide
OH-
Hydroxide
Will a Precipitate Form?
Al2(SO4)3 + NH4OH
Al(OH)3(s) Yes
CaCl2 + K2SO4
CaSO4(s)
Yes
What Happens?
1. Ag(NO3) and Na2SO4
2. NH4Cl and Ba(NO3)2
3. Pb(NO3)2 and HCl
What Happens?
1. Ag(NO3) and Na2SO4
2. NH4Cl and Ba(NO3)2
3. Pb(NO3)2 and HCl
Ag2(SO4)(s) ppt
Remember these
ions
CO32-
Carbonate
PO43-
Phosphate
CrO42- Chromate
S2-
Sulfide
OH-
Hydroxide
What Happens?
1. Ag(NO3) and Na2SO4
Ag2(SO4)(s) ppt
2. NH4Cl and Ba(NO3)2
Nothing
3. Pb(NO3)2 and HCl
What Happens?
1. Ag(NO3) and Na2SO4
Ag2(SO4)(s) ppt
2. NH4Cl and Ba(NO3)2
Nothing
3. Pb(NO3)2 and HCl
PbCl2(s) ppt
1. Identify the correct net ionic equation for the
following reaction and the spectator ions, if
they exist.
FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq)
a) Fe2+(aq) + O2-(aq) + 2H+(aq) + 2ClO4-(aq) 
H2O(l) + Fe2+(aq) + 2ClO4-(aq); no spectator ion
b) O2-(aq) + 2H+(aq)  H2O(l); Fe2+ and ClO4- are
spectator ions
c) FeO(aq) + 2H+(aq)  H2O(l) + Fe2+(aq); ClO4is the spectator ion
d) FeO(aq) + 2HClO4(aq)  H2O(l) +
Fe(ClO4)2(aq); no spectator ion
1. Identify the correct net ionic equation for the
following reaction and the spectator ions, if
they exist.
FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq)
a) Fe2+(aq) + O2-(aq) + 2H+(aq) + 2ClO4-(aq) 
H2O(l) + Fe2+(aq) + 2ClO4-(aq); no spectator ion
b) O2-(aq) + 2H+(aq)  H2O(l); Fe2+ and ClO4- are
spectator ions
c) FeO(aq) + 2H+(aq)  H2O(l) + Fe2+(aq); ClO4is the spectator ion
d) FeO(aq) + 2HClO4(aq)  H2O(l) +
Fe(ClO4)2(aq); no spectator ion
2. Which one of the following products of
double-replacement reactions would
NOT form a precipitate?
a) AgCl
b) PbSO4
c) Mg(OH)2
d) Mo(NO3)2
2. Which one of the following products of
double-replacement reactions would
NOT form a precipitate?
a) AgCl
b) PbSO4
c) Mg(OH)2
d) Mo(NO3)2
3. Which reaction will NOT produce a
precipitate from aqueous solution?
a) Hg2(NO3)2 + KCl
b) FeSO4 + Ba(OH)2
c) Pb(NO3)2 + Na2CO3
d) NaBr + Al2(SO4)2
3. Which reaction will NOT produce a
precipitate from aqueous solution?
a) Hg2(NO3)2 + KCl
b) FeSO4 + Ba(OH)2
c) Pb(NO3)2 + Na2CO3
d) NaBr + Al2(SO4)2
Colors of Some Common Water-Insoluble Materials
Carbonates, CO32Ag2CO3 = yellow
BaCO3 = white
Chlorides, ClAgCl
= white
PbCl2 = white
Hydroxides, OHAgOH = grey-brown
Fe(OH)3= rust red
Pb(OH)2= white
Iodides, IAgI
= yellow
PbI2
= yellow
Sulfides, S2Ag2S
= black
Fe2S3 = black
NiS
= black
Sulfates, SO42BaSO4 = white
CuCO3 = pale blue
CaCO3 = white
Hg2Cl2
CuCl
= white
= white
Cu(OH)2 = pale blue
Ni(OH)2 = pale green
Zn(OH)2 = white
Hg2I2
CuI
= yellow-orange
= brown
CuS
HgS
PbS
= black
= black
= black
PbSO4 = white