Precipitation Reaction Lab
In this lab we will be mixing two different ionic solutions and watching for a
precipitation to take place. You will obtain two reactants, be careful to make sure the
reactants have different cations and anions. For example you don’t want to mix AgNO3
with KNO3 because there are two nitrates, NO3-. You predict what will occur when you
mix the reactants. When you mix the reactants they will undergo a double replacement
reaction.
If you choose sodium phosphate and calcium chloride your product would be
sodium chloride and calcium phosphate. All you have to do is switch the anions.
The full molecular equation for this would be:
Na3PO4 + CaCl2 → NaCl + Ca3(PO4)2
or balanced as
2 Na3PO4 + 3 CaCl2 → 6 NaCl + Ca3(PO4)2
Using your solubility rules sheet, you should be able to determine everything is
aqueous except for Ca3(PO4)2. Therefore, when mixing them you should see a
precipitate. There will also be Na+ Cl- spectator ions in solution. You can determine this
by writing the net ionic equation.
6 Na+ + 2 PO43- + 3 Ca2+ + 6 Cl- → 6 Na+ + 6 Cl- + Ca3(PO4)2
3 Ca2+ + 2 PO43- → Ca3(PO4)2
Procedure:
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Obtain a spot plate.
Obtain two reactants. Make sure the cations and anions are both different.
Predict the products of the double replacement reactions.
Write the full molecular equation.
Determine if there will be a precipitate or not.
Write and balance the net ionic equation.
Label any spectator ions in the solution.
Mix the reactants in the spot plate to see your reaction. There is a possibility that
the reaction won’t follow the rules as it is supposed to.
9. Write down any observations you make about your product.
10. Complete this another 2 more times (a total of three reactions).
11. Type a report with all required data (everything in bold above) to hand in.