Sage Dieterle
Chemistry – D
October 23, 2012
Water Softening
I.
Statement of Problem and Hypothesis
What is the most effective way to soften water? If we attempt to soften water with sand,
calgon, and ion exchange, then the ion exchange will produce the best results because
instead of filtering the calcium, it exchanges hard water ions with sodium. Calgon
“removes” hard water cations by causing them to be part of larger soluble anions while
also softening water by removing hard water cations as precipitates such as calcium
carbonate. When hard water is passed through an ion exchange resin such as those found
in home water softening units the resin contains millions of tiny insoluble porous beads
capable of attracting cations. Cations causing water hardness are contained on the ion
exchange resin and those that do not cause hardness (often sodium) are released from the
resin into the water taking the place of the ions that harden water. The independent
variable is the type of filtration and the dependent variable is the effectiveness of the
water softening.
II.
Experimental Design
Reference procedure from Water Softening, D.5, page 77-79 of Chemistry in the
Community. Instead of setting up four funnels, one for each filtration method, set up two
funnels for each substance at one given time, each with a test tube below and filter 5 mL
of hard water through each adding sodium carbonate to one and ivory soap to the other.
The control in this experiment is the funnel with only filter paper in it because hard water
ions in a solution cannot be removed by filter paper alone. The variables that should be
held constant are the amount of hard water, amount of ivory soap, and amount of sodium
carbonate. For safety, be sure to wear closed toed shoes, tie up your hair, wear safety
goggles, and be sure to wash your hands after the lab.
III.
Data and Observation
Test
Filter Paper
Reaction with
sodium
carbonate
(Na2CO3)
Degree of
cloudiness
(turbidity) with
ivory soap
Heights of suds
IV.
Filter paper &
sand
Filter paper &
calgon
Filter paper &
ion exchange
resin
No apparent
precipitate
Precipitate still
present
Slight
precipitate
No apparent
precipitate
Much Turbidity
No apparent
turbidity
Slight turbidity
No apparent
turbidity
10.5 cm
9cm
4cm
11cm
Data Analysis
2 Ca2+ (aq) + (P6O18)6- (aq)  [Ca2P6O18)]2- (aq)
Calcium ion from
hard water
Hexametaphosphate
Calcium Hexametaphosphate
ion
ion
Ca2+ (aq) + CO32- (aq)  CaCO3(s)
Calcium ion
from hard water
V.
Carbonate ion from
sodium carbonate
Calcium Carbonate
precipitate
Conclusions
The data supported the hypothesis because the ion exchange was the most effective in
producing no turbidity or reaction with the sodium carbonate as well as producing the
highest height of suds at 11cm when shaken meaning that the water was the cleanest and
the softest. The filter paper and calgon did not react with the filter paper and calgon and
contained slight turbidity. The height of the suds was 4 cm. This means that the calgon
removed some of the calcium, but not very much because the height of the bubbles was
still small suggesting the water remained hard. The filter paper and sand had a slight
reaction with the sodium carbonate, no turbidity, and a height of 9 cm indicating that
there was calcium still in the solution; however the water was still soft since the height of
the suds was still high compared to the other substances. The control, filter paper alone,
showed the presence of calcium, much turbidity, and a height of 10.5 cm of suds. These
suds should not have been so high because the calcium was still present making the water
hard and should have prevented the formation of suds. As a result, this data is not reliable
because the height of the suds did not correspond with the hardness of the water that
should have occurred with each test. There may have been human error in measuring the
soap and suds as well as over shaking the test tubes. The conclusions are not valid
VI.
because they results did not complete match the expected results. This experiment could
be improved if the correct amount soap was more easily obtained.
Questions
1) Filter paper and the ion exchange was the best water softening method because
the ion exchange resin caused the cations that are responsible for water hardness
to be exchanged for another cation such as sodium that will not result in hard
water.
2) The amount of ion remaining resulted in more turbidity in the filtrate when the
ivory soap was added.
3) The effect of this relationship is that the more turbidity in the filtrate, the more
suds will occur.
4) According to our results, the advertising claim that Calgon prevents bathtub ring
is false because there was slight turbidity and very little suds suggesting the water
was still very hard. Since bathtub ring is caused by hard water ions reacting with
soap, Calgon would not prevent this; however, our results may have been skewed
due to human error and if tested again this may be proven different.