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REACTIONS BETWEEN IONS - DOC - DOC by 9uJXRvyL

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									                                                                                          Exp. 30, p. 1

                               REACTIONS BETWEEN IONS
                                IN AQUEOUS SOLUTIONS

Purpose:

        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
reaction.

Theory:

        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
equation:

        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.

Equipment:

       Glass plates or plastic sheets

Chemicals:

       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

Procedure:


 SAFETY PROCEDURE
       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
teacher directs.

       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
took place.

SOLUBILITY RULES

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?



SET 1:
                     Ba(NO3)2    BaCl2      K2CO3       Na2CO3      NaNO3       SrCl2
         Ba(NO3)2
         BaCl2
         K2CO3
         Na2CO3
         NaNO3
         SrCl2


SET 2:

                     Na2SO4      Al2(SO4)3 Sr(NO3)2     BaCl2       Ba(NO3)2    AlCl3
         Na2SO4
         Al2(SO4)3
         Sr(NO3)2
         BaCl2
         Ba(NO3)2
         AlCl3


SET 3:

                     FeCl3       Co(NO3)2 CoCl2         NaOH        KOH         NaNO3
         FeCl3
         Co(NO3)2
         CoCl2
         NaOH
         KOH
         NaNO3
                                                                         Exp. 30, p. 4

SET 4:

                     Co(NO3)2 MgCl2      Na2SO4   NaOH     Ba(OH)2   MgSO4
         Co(NO3)2
         MgCl2
         Na2SO4
         NaOH
         Ba(OH)2
         MgSO4


SET 5:

                     BaCl2    Sr(NO3)2   Na2CO3   Al2(SO4)3 K2CO3    AgNO3
         BaCl2
         Sr(NO3)2
         Na2CO3
         Al2(SO4)3
         K2CO3
         AgNO3

								
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