David Millard
Naomi Bryner (Partner)
Real World: Determining Hardness of Water from Various Sources
Introduction:
Samples of water from various sources will be tested to determine the concentration of Ca 2+ that
each sample contains. A lower limit and upper limit will be found to help determine if the
procedure will work. A spike of a known concentration will be added to each sample to prove
that the procedure will work. The concentrations will be compared to any water reports that can
be found for the samples. Samples will include: Tap water from Brockie Commons, tap water
from Brockie Commons filtered through a Brita® water filter, well water (untreated), well water
(treated), water from a water fountain (Campbell Hall), Tyler Run Creek, Aquafina®, Dasani®,
Fiji®, and Acadia®.
Procedure:
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After collection of the samples, allow all samples to reach room temperatures.
Calibrate a pH meter (everyday).
Record the pH and temperature of the samples of water that will be tested that day.
Create an ammonia buffer with a pH of 10.
Prepare an EDTA solution by dissolving 0.7445g of EDTA along with 8mL of ammonia
and dilute to 2L
Prepare a calcium carbonate solution by dissolving 0.25g of CaCO3 in a 100mL
volumetric flask with 0.1M HCl and diluting with 0.1M HCl.
o Perform a serial dilution of the CaCO3 solution.
Standardize the EDTA solution by titrating with 3mL of the CaCO3 solution, 5mL of
ammonia buffer and 10 drops of calmagite indicator.
A spike will be added to each sample of water to make sure that the Ca2+ is detectable.
o Create a 1000ppm sample of Ca2+ solution and then dilute down to 24ppm.
o Add a small sample (1mL) of the 24ppm sample to each sample of water and
titrate to make sure that the spike can be recovered.
Titrate each sample of water by adding 25mL of water, 3mL of ammonia buffer and 10
drops of calmigite indicator.
Data: (Bolded trials were rushed trials and not included in averages)
Day 2: Ammonia pH: 9.99, CaCO3 Molarity: 0.01M
Standardizing EDTA
Trial 1
Trial 2
Trial 3
Trial 4
Average
Molarity (M)
Standard Deviation
Relative Standard
Deviation (RSD) (%)
EDTA (mL)
30.00
26.69
29.54
29.24
29.49
1.0173*10-3M
.2291288
0.77697112
Water fountain water: 7.76 pH, 25°C
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
21.30
19.61
19.99
19.92
19.80
19.83
0.166333
0.83879475
8.0692*10-4M
32.3396
Brockie Commons (untreated): 7.43 pH, 25°C
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
19.86
19.58
22.50
20.6467
1.611128
7.8033321
8.4015*10-4M
33.6715
Day 3: Ammonia pH: 10.06, CaCO3 Molarity: 1*10-6M
Standardizing EDTA
Trial 1
Trial 2
Trial 3
Average
Molarity (M)
Standard Deviation
Relative Standard
Deviation (RSD) (%)
EDTA (mL)
27.63
28.54
29.13
28.433
1.0551*10-7M
.7556675
2.6576816
Acadia bottled water: 6.85 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
Trial 4
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
5.80
5.34
5.28
5.37
5.33
0.0458258
0.8597703
2.2495*10-8M
9.0154*10-4
Without Spike
Trial 1
Trial 2
Trial 3
Trial 4
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
5.90
5.00
5.09
5.41
5.167
0.215484
4.1706571
2.1805*10-8M
8.73917*10-4
Without Spike
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
0.32
0.28
0.59
0.397
0.1686219
42.509714
1.6741*10-9M
6.70942*10-5
Aquafina bottled water: 6.22 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
0.22
0.52
0.38
0.373
0.1501111
40.208322
1.57656*10-9M
6.31475*10-5
Day 4: Ammonia pH: 10.01, CaCO3 Molarity: 1.76*10-7
Standardizing EDTA
Trial 1
Trial 2
Trial 3
Average
Molarity (M)
Standard Deviation
Relative Standard
Deviation (RSD) (%)
EDTA (mL)
0.39
0.47
0.48
0.4467
1.1821*10-6M
0.0493288
11.043768
Fiji bottled water: 7.30 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
28.04
27.21
28.28
27.843
0.5614564
2.0164843
1.3165*10-6M
5.2764*10-2
Without Spike
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
26.85
26.42
26.32
26.53
0.2816026
1.0614495
1.2544*10-6M
5.0275*10-2
Without Spike
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
3.40
3.29
3.59
3.4267
0.1517674
4.4290087
1.6203*10-7M
6.493641*10-3
Dasani bottled water: 6.07 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
3.34
3.44
3.49
3.423
0.0763763
2.2310495
1.6187*10-7M
6.487324*10-3
Tyler Run Creek: 7.48 pH, 24°C
Trial 1
Trial 2
Trial 3
Trial 4
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
36.39
37.45
37.50
37.14
37.363
0.1950214
0.5219592
1.7667*10-6M
7.080469*10-2
Brockie Commons (treated): 4.43 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
EDTA (mL)
8.52
8.47
8.51
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
8.50
0.0264575
0.3112649
4.0191*10-7M
1.6107767*10-2
Day 5: Ammonia pH: 10.05, CaCO3 Molarity: 0.0496
Standardizing EDTA
Trial 1
Trial 2
Trial 3
Average
Molarity (M)
Standard Deviation
Relative Standard
Deviation (RSD) (%)
EDTA (mL)
109.40
108.59
110.44
109.4767
1.359*10-3M
0.9273798
0.8471027
Without Spike
Trial 1
Trial 2
Trial 3
Trial 4
Average
Standard Deviation
RSD (%)
Ca2+ Concentration
Hardness (ppm)
EDTA (mL)
9.40
8.09
8.17
8.19
8.15
0.052915
0.6492641
3.8536*10-7M
1.5444506*10-2
Well water (treated): 6.64 pH, 24°C
Spiked
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
27.74
24.99
24.84
25.857
1.632738
6.3145726
1.40577*10-3M
56.3404
Without Spike
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
24.61
24.47
23.99
24.357
0.3251666
1.335021
1.32422*10-3M
53.0720
Well water (untreated): 6.87 pH, 24°C
Trial 1
Trial 2
Trial 3
Average
Standard Deviation
RSD (%)
2+
Ca Concentration
Hardness (ppm)
EDTA (mL)
27.69
27.42
27.39
27.50
0.1652271
0.6008259
1.49511*10-3M
59.9211
Calculations:
Molarity of EDTA
M CaCO3 ∗ L CaCO3
= M EDTA
L EDTA
0.01M ∗ 0.003L
= 0.0010173M
0.02949L
Standard Deviation
√
∑(x − x̅)2
n
(29.69 − 29.49)2 + (29.59 − 29.49)2 + (29.24 − 29.49)2
√
= 0.2291288
3
Relative Standard Deviation
Standard Deviation
∗ 100
x̅
0.2291288
∗ 100 = 0.77697112%
24.49
Ca2+ Concentration
L EDTA ∗ M EDTA ∗
0.024350L ∗ 1.359 ∗ 10−3 ∗
mol Ca2+
1
∗
= M Ca2+
mol EDTA L Ca2+
1mol Ca2+
1
∗
= 0.00132422M Ca2+
1mol EDTA 0.025L Ca2+
Hardness of Water
M Ca2+ ∗
0.00132422M ∗
g Ca2+
mg
∗
= ppm Ca2+
2+
mol Ca
g
40.078g Ca2+ 1000mg
∗
= 53.07197511ppm Ca2+
1mol Ca2+
1g
Conclusion:
The main goal of this real world experiment was to determine the Ca2+ concentration and
hardness of water in the different samples. We were able to complete this task even with the
problems that we had faced with this experiment. The main problem was the lack of information
with regards to the water. There was little, to no information when it came to the calcium
concentration and hardness of water with some of the samples. Others, like water from the York
Water Company and Fiji water, had their information readily available on their website and on
the bottle itself.