UMass
Amherst
Department
of
Chemistry
Lecture
Demonstrations
4.3
Various
Precipitation
Reactions
Subject:
Chemical
reactions,
precipitation
reactions,
Net
ionic
equations
Description:
Various
clear
solutions
are
mixed
to
form
precipitates.
Materials:
Reaction
A:
‡
Reaction
B:
‡
Reaction
C:
‡
0.1M
CuSO4
0.1M
Fe(NO3)3
or
FeCl3
0.1M
CuSO4
0.1M
Na2CO3
0.1M
NaOH
0.1M
CaCl2
Reaction
D:
‡
Reaction
E:
‡
Reaction
F:
‡
0.1M
KI
or
NI
0.1M
Na2CO3
0.1M
AgNO3
0.1M
Pb(NO3)2
0.1M
FeCl3
0.1M
KCl
or
KI
For
each
reaction
A‐F
the
following
supplies
are
located
in
the
bin:
2
100
mL
beakers
1
300
mL
beaker
Reaction
G:
Solid
KI
or
NaI‡
Solid
NaNO3
or
KNO3‡
0.1M
Pb(NO3)2‡
Supplies
in
bin:
2
300
mL
beakers
2
watch
glasses
2
spatulas
‡Solutions
for
all
reactions
are
stored
in
the
solutions
cabinets.
Sodium
hydroxide
is
stored
in
the
cabinet
under
the
hood.
Preparation:
1.
Rinse
all
beakers
thoroughly
with
dI
water.
Be
sure
to
pre‐label
all
beakers
to
avoid
confusion
Procedure:
1.
For
reactions
A‐F:
Pour
each
individual
solution
into
a
pre‐labeled
100
mL
beaker.
2.
Pour
the
contents
of
both
beakers
simultaneously
into
the
300
mL
beaker
to
form
the
precipitate.
See
reactions
below.
For
Reaction
G:
1.
Place
a
few
scoops
of
NaI
and
NaNO3
on
labeled
watch
glasses.
1
UMass
Amherst
Department
of
Chemistry
Lecture
Demonstrations
2.
Pour
Pb(NO3)2
into
each
300
mL
beaker.
Add
NaNO3
to
first
beaker.
No
reaction.
3.
Add
NaI
or
KI
to
second
beaker.
A
yellow
precipitate
of
lead
iodide
will
precipitate.
Discussion:
A
precipitation
reaction
produces
a
water‐insoluble
solid
product
called
a
precipitate.
The
reactants
are
generally
water‐soluble
ionic
compounds
that
dissolve
to
produce
an
aqueous
solution
of
anions
and
cations.
When
the
cation
from
one
reactant
can
form
a
precipitate
with
the
anion
of
another
reactant,
a
precipitation
reaction
occurs.
Detailed
below
are
the
reactions
for
demos
A‐G.
A:
CuSO4(aq)
+
Na2CO3(aq)

CuCO3(s)
+
Na2SO4(aq)
Net
ionic
equation:
Cu+2(aq)
+
CO3‐2(aq)

CuCO3(s)
B:
Fe(NO3)3(aq)
+
3NaOH(aq)

Fe(OH)3(s)
+
3Na(NO3)(aq)
Net
ionic
equation:
Fe3+(aq)+
3
OH‐(aq)

Fe(OH)3(s)
Alt:
FeCl3(aq)
+
3NaOH(aq)

Fe(OH)3(s)
+
3NaCl(aq)
Net
ionic
equation:
Fe3+(aq)
+
3OH‐(aq)

Fe(OH)3(s)
C:
CuSO4(aq)
+
CaCl2(aq)

CuCl2(aq)
+
CaSO4(s)
Net
ionic
equation:
Ca+2(aq)
+
SO42‐(aq)

CaSO4(s)
D:
NaI(or
KI)(aq)
+
Pb(NO3)3(aq)

PbI3(s)
+
3KNO3
(or
NaNO3)(aq)
Net
ionic
equation:
Pb3+(aq)
+
3I‐(aq)

PbI3(s)
E:
3Na2CO3(aq)
+
2FeCl3
(aq)

Fe2(CO3)3(s)
+
6NaCl(aq)
Net
ionic
equation:
2Fe+3(aq)
+
3(CO3)2‐

Fe2(CO3)3(s)
F:
AgNO3(aq)
+
KCl(or
KI)(aq)

AgCl
(or
AgI)(s)
+
KNO3(aq)
Net
ionic
equation:
Ag+1(aq)
+
Cl(or
I)‐1(aq)

AgCl(s)
or
AgI(s)
G:
Pb(NO3)3(aq)
+
NaNO3

no
reaction.
Both
reactants
are
nitrate
salts,
which
are
water‐soluble.
No
precipitation
occurs.
NaI(s)

Na+(aq)
+
I‐(aq)
Pb(NO3)3(aq)
+
3NaI(aq)

PbI3(aq)
+
3Na(NO3)
2
UMass
Amherst
Department
of
Chemistry
Lecture
Demonstrations
Net
Ionic
equation:
Pb3+(aq)
+
3I‐(aq)

PbI3(s)
Safety:
Lead
is
toxic.
Silver
nitrate
can
cause
skin
irritations.
Sodium
hydroxide
is
caustic
and
can
cause
skin
irritations
or
burns.
Use
appropriate
protective
equipment,
including
gloves
and
safety
glasses.
Disposal:
Dispose
of
solutions
in
proper
aqueous
waste
containers.
The
solution
containing
iron
hydroxide
from
reaction
B
can
be
saved
and
reused
for
Demo
4.10
–
Hydroxide
Clean‐up.
The
solution
containing
iron
carbonate
from
reaction
E
can
be
saved
and
reused
for
Demo
4.4
–
Carbonates
in
acid.
References:
1.
Prof.
Botch
3