Observing Precipitation Reactions
Purpose: To observe the results of mixing solutions of soluble
ionic compounds and to write net ionic equations for the reactions
that form precipitates.
Procedure:
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Copy the sample grid onto five separate pages in your lab notebook or onto five separate
pieces of notebook paper. Make the squares large enough that you can record observations
in the squares. Number each square with a small numeral in a lower corner of the square.
In the lab you will find five sets of solutions containing 6 bottles in each set. Select one set
and write the names (or formulas) of the solutions along each side of the grid on your paper.
You may work with the sets in any order. Use the sets as they become available from other
lab groups.
After labeling the grid on your paper, lay out the grid on the transparency sheet at your lab
station so it matches the grid on your paper.
In each square place ONE DROP of EACH of two solutions according to the grid labels on
your paper. Be careful to keep the dropper tips from touching the drops of solution on
your transparency sheet - hold the dropper bottles slightly above the transparency
sheet and allow the drop to fall into the square. Record what happens – watch carefully
for the formation of a precipitate.
When you have completed your observations with one set, wipe off the transparency sheet
with a paper towel and place the paper towel into the trash. Rinse the transparency sheet
with distilled water and dry it with a paper towel. Then test the combinations in each of the
other sets, recording your observations on a new grid for each new set until you have worked
with all five sets of solutions.
Clean up your lab station, leaving the transparency sheet clean and rinsed for the next class.
Wash your hands!!
Data Analysis:
 For each square where you observed a precipitate forming, write
the net ionic equation for the reaction that formed the precipitate.
Remember that you will need to write the full ionic equation first,
then identify the spectator ions and eliminate them. You may need
to use the Solubility Guidelines Table to identify the precipitate that
formed. Use the left hand page of your notebook (or the back of
your notebook paper sheets) to write the full ionic equation and
identify the spectator ions. Then write the net ionic equation below
the grid where you wrote your observations, using the numbers in
the squares as a key to identify the equation that describes the
reaction in each square. Many squares will have no reaction, and
therefore no equation!