Exp. 30, p. 1
REACTIONS BETWEEN IONS
IN AQUEOUS SOLUTIONS
In this experiment you will combine solutions of different ionic substances which dissolve in
water to see if an insoluble substance will form. The insoluble substance will precipitate from the
solution. From the combinations of ions that you start with, you will try to deduce the formula of the
insoluble precipitate. Once you know its formula, you will be able to write a net ionic equation for the
Many ionic compounds, like NaCl or Pb(NO3)2, dissolve readily in water. When these
compounds dissolve the positive and negative ions separate from each other. Each ion becomes
surrounded by water molecules and moves independently through the solution. However, there are
also many other ionic compounds, like PbCl2, which hardly dissolve at all. If a solution of NaCl is
mixed with a solution of Pb(NO3)2, the Pb2+ ions will combine with the Cl ions to form the insoluble
precipitate, PbCl2. The Na+ ions and the NO3 ions will remain in solution.
We can write an equation to show reactions such as this. A "molecular" equation would be:
2 NaCl(aq) + Pb(NO3)2(aq) PbCl2(s) + 2 NaNO3(aq)
Here the symbol "aq" means aqueous, and "s" means the formation of a solid.
Since the solutions really contain independent ions, a more proper equation would be an ionic
2 Na+(aq) + 2 Cl(aq) + Pb2+(aq) + 2 NO3(aq) PbCl2(s) + 2 Na+(aq) + 2 NO3(aq)
In this equation you can see that the Na+ ions and the NO3 ions do not really react. They are
called "spectator" ions. An equation that shows only the substances that take part in the reaction is
called a "net ionic equation". In a net ionic equation, spectator ions are not included:
Pb2+(aq) + 2 Cl(aq) PbCl2(s)
Notice that in a net ionic equation both atoms and charges must balance.
Glass plates or plastic sheets
Sets of chemical solutions:
Exp. 30, p. 2
Set 1: Set 2: Set 3: Set 4: Set 5:
Ba(NO3)2 Na2SO4 FeCl3 Co(NO3)2 BaCl2
BaCl2 Al2(SO4)3 Co(NO3)2 MgCl2 Sr(NO3)2
K2CO3 Sr(NO3)2 CoCl2 Na2SO4 Na2CO3
Na2CO3 BaCl2 NaOH NaOH Al2(SO4)3
NaNO3 Ba(NO3)2 KOH Ba(OH)2 K2CO3
SrCl2 AlCl3 NaNO3 MgSO4 AgNO3
Compounds that contain the OH ion are bases and are hazardous to skin and eyes. Use
them carefully. Many of the compounds are poisons. If you spill a compound on yourself, wash it
off with lots of water. Wash your hands before you leave the lab.
Wear your safety goggles and apron.
On a glass plate place two drops of one of the chemical solutions from a set. Place two drops
of a second solution from the set on top of the first one. Be careful not to touch the droppers to the
solutions on the plate. Observe if a reaction occurs, and note the color of any precipitates. Repeat with
all possible combinations of the solutions in a set. Carry out experiments with as many sets as your
For each combination where a precipitate appears, figure out which combination of ions is
responsible for the precipitate. The table of solubility rules will help you with this, and you can also
compare data from different combinations in a set to find similar precipitates.
Write a molecular equation, an ionic equation, and a net ionic equation for each reaction that
1. Salts of the alkali metals (Li+, Na+, K+, etc.) are soluble.
2. Ammonium (NH4+) salts are soluble.
3. Salts containing nitrate (NO3), perchlorate (ClO4), and acetate (C2H3O2) are soluble.
4. All chlorides (Cl), bromides (Br), and iodides (I) are soluble EXCEPT for those of Pb2+, Hg22+,
and Ag+ which are insoluble.
5. All sulfates (SO42) are soluble EXCEPT for those of Sr2+, Ba2+, Hg22+, Hg2+, and Pb2+ which are
insoluble. The sulfate salts of Ca2+ and Ag+ are moderately soluble.
6. All hydroxides (OH) are insoluble EXCEPT for those of the alkali metals, which are soluble, and
the hydroxides of Ca2+, Ba2+ and Sr2+ which are moderately soluble.
7. All sulfites (SO32), carbonates (CO32), chromates (CrO42), and phosphates (PO43), are insoluble
EXCEPT for those of NH4+ and the alkali metals, which are soluble.
8. All sulfides (S2) are insoluble except for those of NH4+, the alkali metals, and the alkaline earths,
which are soluble.
Exp. 30, p. 3
REACTIONS BETWEEN IONS
IN AQUEOUS SOLUTIONS
Name _________________________________ Date _________________ Class _______________
Record your observations in the tables which follow. Use the solubility rules and evidence from the
table to determine the formulas of the precipitates. Write a molecular equation, ionic equation, and
net ionic equation for each reaction that takes place.
Note that it is not necessary to fill in the shaded blocks. Why?
Ba(NO3)2 BaCl2 K2CO3 Na2CO3 NaNO3 SrCl2
Na2SO4 Al2(SO4)3 Sr(NO3)2 BaCl2 Ba(NO3)2 AlCl3
FeCl3 Co(NO3)2 CoCl2 NaOH KOH NaNO3
Exp. 30, p. 4
Co(NO3)2 MgCl2 Na2SO4 NaOH Ba(OH)2 MgSO4
BaCl2 Sr(NO3)2 Na2CO3 Al2(SO4)3 K2CO3 AgNO3