Mackenzie Malone
Nicholas Vatteroni
10/20/11
Water Testing with Ions
The objective of this lab was to use different testing techniques to determine if ions are
present in particular water samples. The four different types of tests used were a calcium ion
(Ca2+) test, an iron (III) Ion (Fe3+) test, a chloride ion (Cl-) test and a sulfate ion (SO42-) test. In
each test, a change in solution color of the appearance of an insoluble material, known as a
precipitate, will determine that an ion is present. If there is no color change or a precipitate
present, there still may be ions present but not in sufficient enough quantities. The purposes of
the first two techniques are to test for the presence of iron and calcium cations. The purposes of
the last two techniques are to test for the presence of chloride and sulfate anions. Each test was
done on several water samples. The first was the reference solution, which contains the ion being
tested. The second is the control, which was distilled water and the other solutions are tap water
and natural water samples. To determine whether the solutions contain the ion, the reference and
control samples are used for comparison. The independent variable of this lab is if the ion is
present, and the dependent variable is specified ion. If the specified ion test produces a
precipitate, than the ion is present in the sample.
Experimental Design
The lab procedure can be located on pages 37-39 in “Chemistry: In the Community.” It is called
B.7 Water Testing.
Data Table: Calcium Ion (Ca2+ Test)
SOLUTION
OBSERVATIONS (color,
precipitate, etc.)
RESULT (is ion present?)
Reference
Precipitate, blue and grey
Yes
Control
Precipitate
Yes
Tap Water
No precipitate, clear
Not enough ions to be shown
Natural Water -#1
No precipitate, clear
Not enough ions to be shown
Natural Water -#2
No precipitate, clear
Not enough ions to be shown
Natural Water -#3
No Precipitate, clear
Not enough ions to be shown
Natural Water -#4
No precipitate, clear
Not enough ions to be shown
Data Table: Iron (III) Ion (Fe3+ Test)
SOLUTION
OBSERVATIONS (color,
precipitate, etc.)
RESULT (is ion present?)
Reference
Change in color, dark red
Yes
Control
No precipitate clear
Not enough ions to be shown
Tap Water
No Precipitate, clear
Not enough ions to be shown
Natural Water -#1
No precipitate, clear
Not enough ions to be shown
Natural Water -#2
No precipitate, clear
Not enough ions to be shown
Natural Water -#3
No precipitate, clear
Not enough ions to be shown
Natural Water -#4
No precipitate, clear
Not enough ions to be shown
Data Table: Ion (Cl- Test)
SOLUTION
OBSERVATIONS (color,
precipitate, etc.)
RESULT (is ion present?)
Reference
Completely white precipitate
Yes
Control
White, precipitate
Yes
Tap Water
Cloudy, precipitate
Yes
Natural Water -#1
Foggy, precipitate
Yes
Natural Water -#2
No precipitate
Not enough ions to be shown
Natural Water -#3
Barely cloudy, slight precipitate
Yes
Natural Water -#4
Fairly cloudy, precipitate
Yes
Data Table: Sulfate Ion (SO4 2- Test)
SOLUTION
OBSERVATIONS (color,
precipitate, etc.)
RESULT (is ion present?)
Reference
Precipitate, cloudy white
Yes
Control
Barely cloudy
Yes
Tap Water
No precipitate
Not enough ions to be shown
Natural Water -#1
No precipitate
Not enough ions to be shown
Natural Water -#2
No precipitate
Not enough ions to be shown
Natural Water -#3
No precipitate
Not enough ions to be shown
Natural Water -#4
No precipitate
Not enough ions to be shown
Conclusion:
The hypothesis of this experiment did prove to be true because certain solutions did result in the
ion being present. Any changes in color and the presence of a precipitate represents that an ion
is present. As seen in the data tables of each specified ion test, the reference solution underwent
a change in color and formed a precipitate. The control solution, which was distilled water,
formed a precipitate from the calcium ion test, the chloride ion test, and the sulfate ion test. The
control solution in the iron ion test did not result in significant enough amount of an ion presence
to produce a precipitate. The calcium ion test, iron ion test and the sulfate ion test all did not
produce enough presence of an ion to result in a precipitate. But the chloride ion test produced a
somewhat cloudy and foggy precipitate for all of the solutions, except for the second natural
water sample.
Questions
1. a. A control was used in each test because it allows you to compare the test solutions with
the reference, tap water and the natural water samples.
b. Distilled water was chosen as the control because it is known that the sample
wouldn’t contain the ion.
1. The difficulties associated with the use of qualitative tests are that the water samples
can’t accurately be tested for containing ions because they will always contain ions but
not in significant enough amounts.
2. These tests can not absolutely confirm the absence of an ion because like previously
stated, the samples will always contain ions but not in large enough amounts to be
registered. The only sample that wouldn’t contain any ions would be distilled.
3. Your observations could have changed if you had not thoroughly cleaned the wells or
stirring rods between each test because there could be the chance of cross-contaminating
the specified ions with the water samples.