Almarzooqi 1
An Analysis of Water Hardness for Different Commercial Brands Using
EDTA and AA
Samar Almarzooqi
11/14/12
Chem 111
Section 105
Group Members: Laura Bleiel, Mariam Ahmad, Taylor Blackford
TA: Jamie Bingaman
Almarzooqi 2
Introduction
Water hardness defines the sum of the concentrations of Mg2+ and Ca2+ ions in a
sample of water, measured by the amount of calcium carbonate (CaCO3). Water is often
defined in terms of water hardness in order to measure the overall quality of the water.
Water with a large concentration of Mg2+ and Ca2+ ions is said to be ‘hard’ while water
with a small concentration of Mg2+ and Ca2+ ions is defined as ‘soft’.1 Water levels
containing concentrations of Mg2+ and Ca2+ ions above 100 milligrams per liter (mg/l) are
classified as hard while those below are classified as soft.2 Hard water is not a health
hazard, and the minerals present in hard water are a part of the daily nutrients people
need.3 Hard water causes complications in industries when hard water is heated, leaving
behind the crystalline CaCO3, causing complications in heat transfer and further
malfunctions and damage.4 The formation of scale, the CaCO3 crystalline deposit, is
expensive to remove, which is why industries are concerned about measuring the
hardness of the water used. Hard water also results in scum when Ca2+ ions bind with the
soap, creating an insoluble compound. To eliminate the hardness of the water by
removing the Mg2+ and Ca2+ ions, water softeners are often used in the form of the
addition of lime and washing soda. These compounds bind with either the Mg2+ or Ca2+
ions and precipitate them out of solution, making them insoluble salts that can be
Thompson, Stephen. PSU CHEMTREK: Small-Scale Experiments for General
Chemistry. New Jersey: Hayden McNeil, 2012. Print
2 FAQ. SCBWA: State College Borough Water Authority. Web. 11 Nov. 2012.
<http://www.scbwa.org/pages/faq>
3 Robillard, Sharpe, and Swistock. Water Softening. State College: The Pennsylvania
State University, 2012. Print
4 D. Spurlock. Determination of Water Hardness by Complexometric Titration. Indiana
University Southeast, 2012. Web. 12 Nov. 2012.
<http://homepages.ius.edu/DSPURLOC/c121/week13.htm >
1
Almarzooqi 3
removed by filtration. Another softening technique is the ion exchange method. This
method exchanges monovalent cations like Na+ and H+ with the Mg2+ and Ca2+ ions.1
Water hardness can be measured by using two different techniques, EDTA and
AA (Atomic Absorption Spectroscopy). Both methods of calculating water hardness were
used in the lab to verify the hardness of the water sample. Getting two different sources
of evidence provides stronger evidence for the hardness of the water calculated and
eliminates sources of error that can influence the results. AA is used to detect the
presence of metals in a solution by projecting monochromatic light through the water.
The atoms in the water absorb the energy from the light, and the change in Energy (ΔE)
is measured by the Atomic Absorption Spectrophotometer at the known specific
wavelengths.1 For the Mg2+ ions, the absorbance was measured at the wavelength 422.7
nm and Ca2+ ions were measured at the wavelength 202.5 nm. The amount of absorbance
is directly proportional to the concentration of Mg2+ and Ca2+ ions, and using the BeerLambert law, the concentration can be calculated. The Beer-Lambert Law addresses the
linear relationship between absorbance and the concentration of metal ions in the
solution, described the by the equation ℷ = 𝑎𝑏𝑐 where ‘a’ is the constant molar
absorbance, ‘b’ is the path length of light taken, and ‘c’ is the absorbance, which is
proportional to the concentration.5 A graph of Absorbance vs. Concentration can be
graphed to provide a line-of-best-fit equation for each metal ion.
The other technique in determining the hardness of water is EDTA titration.
Ethylenediaminetetraacetic acid (EDTA) is used with eriochrome black (EBT) to detect
Mg2+ and Ca2+ ions.
5
Beer-Lambert Law. The University of Adelaide: Department of Chemistry. Web. 11
Nov. 2012. <http://www.chemistry.adelaide.edu.au/external/soc->
Almarzooqi 4
The chemical reaction is:
HD2= + Mg2+ + Ca2+
Blue
-
Red
+ H+ + Ca2+
CaEDTA + MgEDTA + HD2Immediately Eventually Blue
The indicator is added and if no Mg2+ is in the sample of water, then the color of the
solution will be blue both at the start and end of the reaction. If there is Mg2+ in the
sample, then it will react to turn the sample a purple color. The CaEDTA is formed
immediately once the EDTA is added, and once all of the Ca2+ has reacted, the EDTA
bonds with the Mg2+ ions. As the MgEDTA chelate is formed, the solution begins to turn
blue as the Mg2+ is taken out of solution. The number of drops it takes in the titration for
the solution to turn blue again is used in the equation MEDTAVEDTA= MCa2+VCa2+, where
the volume is the number of drops and molarity is the concentration of the Ca2+ ions.
From the molarity, the hardness in parts per million (ppm) is calculated to give the
hardness of the sample of water.1
Both EDTA and AA provide the hardness of water, but they each do so using
different chemistry tools and techniques. AA measures the change in energy of the water
sample once a light is shined through it, and the absorbance value measured is
proportional to the concentration of metal ions. The EDTA titration involves the reaction
of the water sample with the EDTA and by using the number of drops of EDTA used for
the solution to turn blue again, the concentration of the Mg2+ and Ca2+ ions can be
calculated. Using the two differing techniques gives two separate numerical values for
the hardness of water, which should be close in value. The difference can be attributed to
the error involved in each technique influencing the values.
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The water samples for the lab include Dasani, Aquafina, Evian, and tap water
from Stephen Hall. The Dasani, Aquafina, and Evian were bought from McLanahan’s,
which is located on College Ave. These samples were used because the lab was focused
on the differences in the hardness of waters amongst various commercial brands of water.
The tap water from Stephen Hall comes from the Pennsylvania water supply, which does
not soften the water to modify the water quality. The hardness of water in State College is
120-190 mg/l, which is classified as hard.2 The Dasani water, as indicated by the
ingredients on the bottle, contains magnesium sulfate and calcium carbonate, so the water
is expected to be hard.6 The rankings of hardness from hardest to the softest water were
expected to be Tap water, Dasani, Aquafina, and Evian. Due to the higher cost and
reputation of Evian water, it was hypothesized that it would be the softest water,
containing the least amount of Mg2+ and Ca2+ ions. Aquafina water was expected to fall
between Evian and Dasani.
Procedure
The procedure for the “Chemistry of Natural Waters” experiment was taken from
the PSU Chemtrek, written by Stephen Thompson, on pages 10-15 to 10-22.1 The four
water samples were obtained from McLanahan’s store and Stephen Hall on the
University Park campus in State College. Each group member conducted the experiment
using similar tests for each individual water sample in order to determine the hardness of
each water sample. The hardness of the water was first calculated using the AA
technique. Since the Dasani water contained no suspended particles, it did not need to be
filtered through in order to remove any possible particles. The Atomic Absorption
6
Purified Water. Dasani. Web. 8 Nov. 2012. <http://www.dasani.com>
Almarzooqi 6
Spectrometer calculated the absorbance for the Mg2+ and Ca2+ ions by placing a tube into
the water sample. The graphs of light absorbance vs. metal ion concentration were then
made and the values were converted to their “equivalent concentration of CaCO3”1 using
the calculations provided in Section G.1 The sum of the hardness of Mg2+ and Ca2+ ions is
the total hardness value and was compared to the EDTA titration value calculated.
The EDTA titration was used on each water sample in order to determine the
hardness of each sample. Using a 1x12 well strip, one drop of EBT indicator,
NH3/NH4CI/MgEDTA buffer, and the water sample were added to each well strip. A
titration was then done by adding 1 drop of the 2 x 10-4 M EDTA to the first well, 2 drops
to the second, 3 to the third, and so on. The first blue well represents the point where
excess EDTA exists, and is defined at the end point where all of the Mg2+ ions have
bonded with EDTA to form a chelate. Using the equation MEDTAVEDTA= MCa2+VCa2+, the
concentration of both Mg2+ and Ca2+ ions can be calculated. The Dasani water sample had
an EBT buffer mixture colored blue, which means that the water sample was extremely
soft and contained little to no Mg2+ ions. Deviating from the directions given in the PSU
Chemtrek, the Dasani water needed to be concentrated in the experiment so that the
presence of Mg2+ ions could be detected. Therefore, a titration was done in which 10
drops of the water sample was added instead of 1 drop. The Evian water sample tested by
lab member Taylor Blackford needed to be diluted in a 1:1 ratio due to the hardness of
the water sample indicated by the red color when the Ca2+ was added.7
Total Dissolved Solutes (TDS) was examined for the water samples by placing a
drop of the water sample onto Aluminum foil and onto a hot plate. A drop of distilled
7
Blackford, Taylor, Chem 111 Laboratory Notebook, pp. 31-36.
Almarzooqi 7
water and 1.0 x 10 -3 M Ca2+. The remaining residue after the water evaporated was
examined.
The hardness of the water was also determined by EDTA titration after a
softening agent was added to the water sample. Since the Dasani water was determined to
be extremely soft, instead of adding the softening agent to the Dasani water sample, a 1 x
10-3 M Ca2= sample was used. A 1 cm height was measured with the 1 x 10-3 M Ca2+
solution and 20 mg of the commercial softening agent was added; an EDTA titration
similar to the titration conducted previously was done. The final step in determining
water hardness included examining the ion exchange of the divalent cation described in
the Introduction. The pH of the water sample was taken to indicate whether the water is
soft or hard; soft water is classified as acidic and hard water is basic.8
Results
Table 1: AA Standard Obtained by Brown for Ca2+ ions9
Ca2+ concentration (ppm)
Absorbance value (at 422.7
Check Standard (ppm)
nm)
0.00
-
-
1.000
0.01082
1.27
5.00
0.0531
5.09
10.00
0.10000
9.81
25.0
0.23103
24.08
50.0
0.43298
50.45
Water pH Water Hardness. Serenity Water Gardens. Web. 8 Nov. 2012.
<http://serenitywatergardens.com>
9 Brown. AA Standards. 14 Oct. 2012. 11:30 pm.
8
Almarzooqi 8
Table 2: AA Standards Obtained by Brown for Mg2+ ions
Mg2+ concentration (ppm)
Absorbance Value (at 202.5
Check Standard (ppm)
nm)
0.00
-
-
1.000
0.01517
1.48
5.00
0.08718
5.62
10.00
0.18376
10.53
25.0
0.39579
24.72
30.0
0.48868
29.02
Figure 1: Light Absorbance vs. Mg2+ Ion Concentration at 202.5 nm
Light Absorbance vs. Metal Ions [Mg2+]
0.6
Absorbance
0.5
0.4
y = 0.0159x + 0.0083
R² = 0.9972
0.3
Concentration
0.2
Linear (Concentration )
0.1
0
0
10
20
30
Concentration (ppm)
40
Almarzooqi 9
Figure 2: Light Absorbance vs. Ca2+ Ion Concentration at 422.7 nm
Light Absorbance vs. Metal Ions [Ca2+]
0.5
0.45
Absorbance
0.4
y = 0.0085x + 0.01
R² = 0.9987
0.35
0.3
0.25
Series1
0.2
Linear (Series1)
0.15
0.1
0.05
0
0
10
20
30
40
Concentration (ppm)
50
60
Absorbance Unit
ppm
Ca2+
-0.0004
0.00
ppm hardness
(CaCO3)
0.00
Mg2+
0.0621
3.38
13.9
3.38
13.9
Total Hardness
Table 3: AA hardness for Dasani Water Sample
ppm hardness was calculated for AA by using the equations given by the trend lines for
each graph.
Calculations:
For Ca2+ ion hardness, the equation in Figure 2 y= 0.0085x+0.01 was used where y= the
absorbance unit given by the AA for the metal ion.
y= 0.0085x + 0.01
-0.0004= 0.0085x + 0.01
Almarzooqi 10
-0.0104= 0.0085x
x= -1.22 ppm
The concentration of the Ca2+ ions cannot be negative, so the concentration is assumed to
be 0 ppm. Similar calculations were used to calculate the ppm for Mg2+ ions.
The ppm then needs to be converted to its “equivalent concentration of CaCO3”, which
measures true hardness of the water sample.1 Using the molar mass of Mg2+, this can be
done.
2+
𝑔
𝐶𝑎𝐶𝑜3
𝑚𝑜𝑙
𝑔
24.3
𝑀𝑔2+
𝑚𝑜𝑙
100.0
3.38 ppm Mg x
= 13.9 ppm CaCO3
Table 4: EDTA Titration for Dasani Water Sample
Drops of EDTA
ppm hardness
Water Sample
6
12
Softened Water
3
.6
The EDTA titration conducted on the water sample was amplified by a factor of ten since
the water sample was extremely soft. The Softening Agent was added to 1 X 10^-3 M
CaCl2 since the Dasani water was extremely soft.
In order to convert the drops of EDTA to ppm we use the equation MEDTAVEDTA=
MwaterVwater in order to find the concentration of the Ca2+ and Mg2+ ions in the sample.
Since the volume units are on both sides of the equation, the units cancel out and do not
matter. Therefore, the number of drops can be used as the volume.
MEDTAVEDTA= MwaterVwater
(2 x 10-4 M) (6 drops) = (Mwater)(10 drops)
Mwater= 1.2 x 10-4
Almarzooqi 11
The concentration of the Ca2+ and Mg2+ ions needs to be converted to CaCO3 because
numerous cations can contribute to the concentration calculated by EDTA titration. By
using the molar mass of CaCO3 the conversion can be made.
1.2 𝑥 10−4
𝑚𝑜𝑙𝑒𝑠 𝐶𝑎𝐶𝑂3
𝐿
𝑥 100.0
𝑔
𝑚𝑜𝑙
𝑥 1000
𝑚𝑔
𝑔
= 12 𝑝𝑝𝑚
The same calculations must be done for the EDTA titration used for the water sample
after the water has been softened. Since the water sample was extremely soft and needed
to be amplified by a factor of ten, conducting EDTA titration on the Dasani water sample
after the softening agent was added would produce poor results. Instead, CaCl2 was used.
Concentration can also be expressed in grains/gallon by using the conversion between
Molarity= moles/liter to grains/gallon.
1 𝑔𝑟𝑎𝑖𝑛 𝐶𝑜𝐶𝑂3
64.7 𝑚𝑔 𝐶𝑎𝐶𝑂3
=
= 17.1 𝑝𝑝𝑚
𝑔𝑎𝑙𝑙𝑜𝑛
3.780 𝐿
The EDTA titration calculated is converted to ppm hardness, which is ppm 𝐶𝑜𝐶𝑂3
12 𝑝𝑝𝑚 𝑥
1 𝑔𝑟𝑎𝑖𝑛/𝑔𝑎𝑙𝑙𝑜𝑛
= .702 𝑔𝑟𝑎𝑖𝑛/𝑔𝑎𝑙𝑙𝑜𝑛
17.1 𝑝𝑝𝑚
Group member data was exchanged, and calculations similar to the calculations shown
above were performed.
Group Water Sample Data Notations:
1. Samar Almarzooqi- Dasani sample10
2. Taylor Blackford: Evian sample7
3. Mariam Ahmad- Aquafina sample11
4. Laura Bleiel- Tap water (Stephen Hall)12
10
11
Almarzooqi, Samar, Chem 111 Laboratory Notebook, pp. 45-50.
Ahmad, Mariam, Chem 111 Laboratory Notebook, pp. 30-36.
Almarzooqi 12
Table 5: AA Water Results for All Samples
Water Sample Absorbance Units ppm hardness
1. Dasani10
Ca2+
-0.0004
0.00
2+
Mg
0.0621
12.00
Total Hardness:
12.00
2. Evian7
Ca2+
.3002
84.70
Mg2+
.2456
61.55
Total Hardness:
146.25
3. Aquafina11
Ca2+
-0.0031
0.00
2+
Mg
0.0790
18.3
Total Hardness:
18.3
4. Tap Water12
Ca2+
.2647
149.82
2+
Mg
.2778
139.50
Total Hardness:
289.32
Table 6: EDTA Water Results for All Water Samples
Water Sample
1. Dasani10
Water Sample
Softened Water Sample
2. Evian7
Water Sample
Softened Water Sample
3. Aquafina11
Water Sample
Softened Water Sample
4. Tap Water12
Water Sample
Softened Water Sample
12
Drops EDTA
ppm (CaCO3)
grains/gallon
6
3
12
.6
.702
.0351
10
7
40
28
2.34
1.61
11
3
22
.6
1.23
.0351
7
5
280
200
16.37
11.70
Bleiel, Laura, Chem 111 Laboratory Notebook, pp. 41-47.
Almarzooqi 13
Table 7: Additional Data for Comparing Water Hardness Between Water Samples
Water Sample
1. Dasani
2. Evian
3. Aquafina
4. Tap Water
Distilled Water
1 x 10-4 M Ca2+
Total
Dissolved
Solute (TDS)
Faint white
ring
Visible white
circles
Faint white
ring
Prominent
white residue
left after
evaporation
No residue
Prominent
White
residue
pH of sample
pH of resin
sample
6
3
8
3
6
3
Basic
Acidic
-
-
Discussion
The hypothesis for the water hardness amongst the commercial water products
Evian, Dasani, and Aquafina, along with tap water from Stephen Hall, was that the order
of water hardness from hardest to softest water would be: Tap water from Stephen Hall,
Aquafina, Dasani, and Evian. From the results obtained through EDTA titration and AA
from the differing water samples, the hypothesis was rejected. Both tests support the
water hardness rankings in the water samples to be Tap water, Evian, Aquafina, and
Dasani in order from hardest to softest water. From EDTA titration, the total hardness for
the tap water was 289.32 ppm hardness from AA and 280 ppm from EDTA titration11,
which is higher than the State College water hardness range of 120-190 ppm hardness
recorded by the State College Burough Water Authority.2 The large difference in water
hardness value between the value of State College water compared to the dormitory water
(Stephen Hall) can be due to the accumulation of metal ions that can occur as the water
Almarzooqi 14
travels through the pipes in order to reach the dormitories. Since scale, the formation of
CaCO3 deposit, occurs in pipes when hard water is heated, the pipes in State College
could have the metal ions that cause water hardness, like Ca2+ and Mg2+ions, already
present. When the water runs through the pipes, it can pick up more metal ions, causing it
to have a higher concentration of metal ions.
The Evian water had the second highest ppm hardness value, 146.25 ppm from
AA and 40 ppm from EDTA titration, which was not expected.7 Since Evian is often
thought of as the most expensive and high quality water, it was hypothesized that it
would have the softest water value. The hardness of the Evian can be explained when
taking into account that Evian water is taken from springs.13 Spring water is water
accumulated from underground sources in which the water interacts with the soil and
rocks.14 The rocks and soil contain metal ions like Mg2+ and minerals like Ca2+, which
can account for the hardness in the Evian water sample. As the water runs over the rocks
and is held beneath the soil, the concentration of Mg2+ and Ca2+ ions would increase,
making the water hard.
Both Dasani and Aquafina are purified water brands, which explains why they
have the lowest water hardness results from AA and EDTA titration. Purified water can
come from any source, but the water goes through a series of processes like distillation,
reverse osmosis, and deionization in order to remove all impurities in it.15 The AA
Evian Natural Spring Water-Annual Water Quality Report. Evian. NSF
International, 2012 Web. 10 Nov. 2012. <http://www.evian.com>
14 The Water Cycle: Springs. United State Geological Survey. U.S Department of
Interior, 2012. Web. 10 Nov. 2012.
<http://ga.water.usgs.gov/edu/watercyclesprings.html>
15 Stout, John. Purified Water vs. Spring Water. The Phantom Writers. The Defined
Writers, 2012. Web. 10 Nov. 2012.
13
Almarzooqi 15
resulted in a water hardness value of 18.3 ppm hardness for Aquafina and 12.00 ppm for
Dasani. The EDTA titration resulted in a water hardness value of 22 ppm hardness for
Aquafina and 12 ppm hardness for Dasani. 9,10 These two water samples are the softest
water samples observed in the lab, meaning that they have little to no concentrations of
Mg2+ and Ca2+ ions. The expected results from the hypothesis do not support the evidence
for the Dasani and Aquafina water sample hardness values calculated by both AA and
EDTA titration. It was expected that Aquafina would have a higher hardness value
compared to Dasani since the ingredients in Dasani indicate that there is MgSO4 and
CaCO3.6 Both the AA and EDTA titration water hardness results show that Aquafina has
a higher water hardness value than Dasani. The reasons why there could be a difference
in metal ion concentrations between two purified water brands can be due to differing
purifying techniques used by commercial companies. Aquafina is slightly harder than
Dasani (18.3 ppm – 12.00 ppm = 6.3 ppm greater), so the purifying process for the water
does not remove as much of the impurities as the purifying process of Dasani does.
The Total Dissolved Solutes (TDS) and the pH of both the water and resin
samples in Table 7 also provide further evidence to support the hardness values from
EDTA titration and AA from all water samples. The tap water from Stephen Hall was
originally very basic, and the pH of the resin was acidic. Soft water is acidic and hard
water is basic.16 The pH shows that the tap water is hard, as seen by the AA and EDTA
titration results, which showed that the tap water from Stephen Hall has the hardest water.
The Evian water sample had a pH of 8, which indicates that is basic, therefore hard.7 The
pH for both the Dasani and Aquafina water samples were the same, pH 6.9,10 A pH of 6 is
16
Water pH and Water Hardness. Serenity Water Gardnes. 2010. Web. 10 Nov. 2012
Almarzooqi 16
acidic, which is proof of the softness of the two brands. The pH values were the same,
which means that the concentration of Mg2+ and Ca2+ ions in the two water brands is very
similar.
The differences between the hardness values given by EDTA titration and AA
results are not very large, and they can be explained by human error in the lab procedure
and the overall error in the Absorption Spectrophotometer provided by the Check
Standards.9 The differences between EDTA titration and AA for the hardness values is
the biggest for the Evian sample where the EDTA titration produced a value of 40.0 ppm
and the AA produced a 146.25 ppm hardness value. The 106.25 ppm hardness value
(146.25 ppm-40.0 ppm) is very large and occurs as a result of the error associated with
each technique for determining water hardness. The other water samples yielded smaller
differences between EDTA titration and AA water hardness values, yet there was still a
difference. The EDTA titration was all done by hand, so there is a lot of room for human
error in counting the number of drops and the possibility of contaminating a water
sample. Contamination and human error can have big effects, which can account for the
difference between the two water hardness values. AA also has error in the
concentrations that are actually used for each metal ion. The Check Standard column in
Tables 1 and 2 show that for each concentration measured, the actual check standard was
greater. For example, for Ca2+ ions, the concentration calculated to be 25.0 M was
actually 24.08 M.9 Also, the R2 values on the graphs for Ca2+ and Mg2+ are .9987 and
.9782 respectively, meaning that for Ca2+ concentration, 99.87% of the absorbance units
calculated are accounted for by the concentrations according to the trend line. Even
though the Atomic Absorbance Spectrophotometer is a piece of expensive equipment, it
Almarzooqi 17
is not perfect in its calculations. The human and machinery error accounts for the
differences between the EDTA titration and AA water hardness values.
The AA technique is the more precise of the two for determining water hardness
because the AA can produce a value to 4 significant figures, compared to the 2 significant
figures EDTA titration water hardness values have. AA is also done by an expensive
machine, which is programmed to detect the presence of Ca2+ or Mg2+ ions, so the
numbers are more accurate. EDTA detects the presence of all cations, not only the Ca2+
or Mg2+ ions AA detects. EDTA titration is done by hand, which is susceptible to
contamination. The EDTA titration is also not very accurate since the concentration of
hardness is determined when the color change to blue is noticed, not known absolutely.
Being off by even 1 well count (1 drop), can change the water hardness by as much as 20
ppm.10 Therefore, AA is the better of the two techniques and even though there is error in
the concentrations and the check standards, the differences are very small that they do not
affect the ppm hardness greatly. The AA also produces an equation for each metal ion
that allows other absorbance values to be calculated since solving for one variable using
the equations is possible. AA is also much easier to do, and multiple water samples can
be done in a shorter amount of time, so it is more time efficient than EDTA.
The water softening technique resulted in water samples with lower ppm hardness
values, which is shown in Table 6. The Dasani water hardness decreased from 12 ppm to
.6 ppm after the water softening technique was conducted.10 The pH of the resin in Table
7 also show that all water samples had a final pH of 3, which is indicative of soft
water.7,10,11,12 Industries and households can therefore use water softening agents to
decrease the concentrations of Ca2+ or Mg2+ ions in their water supply.
Almarzooqi 18
Conclusion
The EDTA and AA techniques showed that the order of water sample from
highest to lowers water hardness in ppm hardness is Tap Water (Stephen Hall), Evian,
Aquafina, and Dasani, which rejected the hypothesis that Evian would have the softest
water. Water hardness is a problem in industries and can be easily solved by water
softening techniques that remove the Ca2+ or Mg2+ ions that lead to the buildup of the
deposit that blocks pipes and causes energy inefficiencies in heating. Spring water is
harder than purified water due to the minerals and metal ions present in the soil and rocks
the water runs over. State College water is hard, and the values obtained in the lab for
dormitory water had a higher water hardness than that recorded for the range of State
College water. Water hardness, while not harmful to people, can lead to problems that
need to be solved by water softening techniques. These techniques are often used by
industries and households to soften the water by removing the Ca2+ or Mg2+ ions causing
the water hardness and leading to the energy inefficiencies and pipe blockage.
References
Thompson, Stephen. PSU CHEMTREK: Small-Scale Experiments for General
Chemistry. New Jersey: Hayden McNeil, 2012. Print
2
FAQ. SCBWA: State College Borough Water Authority. Web. 11 Nov. 2012.
<http://www.scbwa.org/pages/faq>
3
Robillard, Sharpe, and Swistock. Water Softening. The Pennsylvania State
University, 2012. Print
4
D. Spurlock. Determination of Water Hardness by Complexometric Titration. Indiana
University Southeast, 3 April, 2012. Web. 12 Nov. 2012.
<http://homepages.ius.edu/DSPURLOC/c121/week13.htm >
5
Beer-Lambert Law. The University of Adelaide: Department of Chemistry. Web. 11
Almarzooqi 19
Nov. 2012. <http://www.chemistry.adelaide.edu.au/external/soc->
6
Purified Water. Dasani. Web. 8 Nov. 2012. <http://www.dasani.com>
7
Blackford, Taylor, Chem 111 Laboratory Notebook, pp. 31-36.
8
Water pH Water Hardness. Serenity Water Gardens. Web. 8 Nov. 2012.
http://serenitywatergardens.com
9
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