Reactions of Ions
Introduction:
Ionic compounds are made up of positively and negatively charged particles. In a water
solution, these compounds dissociate, or break up into the ions of which they are made.
For example, in water, solid sodium nitrate, NaNO3 , breaks up into separate Na+ and
NO3- ions; sodium carbonate, Na2 CO3 , breaks up into Na + and CO3 2- ions; and calcium
nitrate, Ca(NO3 )2 , breaks up into Ca 2+ and NO3 - ions. When two ionic compounds are
present in dissociated form in the same solution, different compounds may form. For a
different compound to form, a chemical reaction must occur. A change in the appearance
of the solution indicates that a chemical reaction has taken place.
Problem:
How can you determine which ionic compound has formed in a solution containing
known ions?
Materials:
graduated cylinder
sodium nitrate solution
sodium carbonate solution
4 droppers
test tube rack
grease pencil
white vinegar
4 test tubes
stoppers for test tube
calcium nitrate solution
Procedure:
1. On your table you will find the following chemicals:
Sodium nitrate
Calcium nitrate
Sodium carbonate
Vinegar (acetic acid)
2. Observe the appearance of each solution and record your observations in Data Table I
3. Write the formula for each of the compounds listed.
4. Write the ions that may be present in solution for each of the compounds listed.
Procedure:
5
Add a dropper-full of sodium carbonate solution to one of the test
tubes.
6. To the same test tube, add a dropper full of calcium nitrate solution.
Observe what happens and record in a data table. Do not throw away
the contents of this test tube because it will be used again in the
experiment.
7. To a clean test tube, add a dropper full of sodium nitrate solution.
8. Add a dropper full of vinegar to the sodium nitrate solution. Stopper
the test tube and shake gently. Observe what happens and record in
your data table.
9. Add a dropper full of vinegar to the first test tube that contained the
calcium nitrate and sodium carbonate solutions. Tap the test tube
gently to mix the contents. Observe what happens and record the
information in Data table II.
Observations – Data Table I
SOLUTION
Sodium carbonate
Calcium nitrate
Sodium nitrate
Vinegar (acetic acid)
HC2H3O2 OR
CH3COOH
Observation of appearance
IONS
Data Table II
Reactants
Observations
Sodium carbonate +
calcium nitrate
Sodium nitrate +
acetic acid
Acetic acid + contents
of tube with sodium
carbonate and calcium
nitrate.
Analysis:
1.
a. What was the evidence that a chemical change occurred when the calcium
nitrate and sodium carbonate were mixed?
b. What are the products that formed during this reaction?
c. Based on your observation on what sodium nitrate looks like, what do you
think was the white product of this reaction?
d. What ions remained in solution?
2. What do you think was formed when acetic acid was added to the test tube that
contained the products of the calcium nitrate and sodium carbonate mixture?
3. What do you think would happen if you mixed acetic acid and sodium carbonate?
4. If a gas was formed during the final reaction, what do you think it was?
Conclusion:
1. Write an equation to explain what happened when calcium nitrate was added to
sodium carbonate.
2a. What are spectator ions?
b. During which of the reactions in this lab were spectator ions present?
Identify them.
3. Using the information from the lab, make a general statement about what can
happen when solutions containing different ions are mixed.