Naomi Bryner
Experiment 9: Real world hardness of water
Purpose: The purpose of this experiment is to test the hardness of a various water samples. This will be
found by volumetric analysis via titration with EDTA. Data will be evaluated using weight percent and
ppm of the different water samples.
Procedure:
A pH meter was calibrated and used to test an ammonia buffer. The ammonia was treated with NaOH
until a pH of 10 was obtained. The EDTA solution was made to 0.001 M and 4 mL of ammonia buffer (pH
= 10), which was diluted to 2 L using distilled water. The CaCO3 solution was as 0.01 M for
standardization and 10-6 M. The CaCO3 solution was then used to standardize the EDTA solution, using 3
mL CaCO3 solution, 5 mL ammonia buffer, and 10 drops of calmagite indicator (x 3). The standardized
EDTA was then used to titrate various water sources with an unknown amount of Ca2+, using 25 mL tap
water, 3 mL ammonia buffer, and 10 drops of calmagite indicator (x 3). Water sources will include water
from Brockie Commons, water filtered (via Brita filter) from Brockie Commons, Aquafina bottled water,
Dasani bottled water, Acadia bottled water, Figi bottled water, water from the water fountain in
Campbell Hall, creek water from Tyler Run, and well water from a local residence. A spike of CaCO3 was
used for water sources that have miniscule traces of Ca2+, including bottled water and treated water.
Reactions:
y = EDTA
H6y2+ ↔ H5y+ + H+
H5y+ ↔ H4y + H+
H4y ↔ H3y- + H+
H3y- ↔ H2y2- + H+
H2y2- ↔ Hy3- + H+
Hy3- ↔ y4- + H+
Data:
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Sample 9
Sample 10
well water (untreated)
well water (treated)
Brockie (untreated)
Brockie (treated)
Tyler Run Creek
Dasini bottled
Fiji bottled
Aquafina bottled
water fountain
Acadia bottled
Sample 1
pH = 6.87
Temp = 24
Ammonia pH
10.05
Sample 2
Spiked
pH = 6.64
Temp = 24
Ammonia pH
10.05
Without Spike
Sample 3
pH = 7.43
Temp = 25
Ammonia pH
9.95
Sample 4
Without Spike
pH = 4.43
Temp = 24
Ammonia pH
10.01
Spiked
Sample 5
Without Spike
pH = 7.48
Temp = 24
Ammonia pH
10.01
EDTA (L) [Ca2+]
Ca 2+ ppm
Trial 1
0.02769
Trial 2
0.02742
Trial 3
0.02739
Average
0.0275 0.0014951 59.921143
EDTA (L)
[Ca2+]
Ca 2+ ppm
Trial 1
0.02774
Trial 2
0.02499
Trial 3
0.02484
Average 0.025856667 0.0014058 56.340401
Trial 1
0.02461
Trial 2
0.02447
Trial 3
0.02399
Average 0.024356667 0.0013242 53.071975
EDTA (L)
[Ca2+]
Ca 2+ ppm
Trial 1
0.01986
Trial 2
0.01958
Trial 3
0.0225
Average 0.020646667 0.0008401
33.6715
[Ca2+]
EDTA (L)
Ca 2+ ppm
Trial 1 (rough)
Trial 2
Trial 3
Trial 4
Average
0.0094
0.00809
0.00817
0.00819
0.00815
3.854E-07
0.0154445
Trial 1
Trial 2
Trial 3
Average
0.00852
0.00847
0.00851
0.0085
4.019E-07
0.0161078
EDTA (L)
Trial 1 (rough)
Trial 2
Trial 3
Trial 4
Average
0.03639
0.03745
0.0375
0.03714
0.037363333
[Ca2+]
Ca 2+ ppm
1.767E-06
0.0708047
Sample 6
Spiked
pH = 6.07
Temp = 24
Ammonia pH
10.01
Without Spike
Sample 7
Spiked
pH = 7.3
Temp = 24
Ammonia pH
10.01
Without Spike
Sample 8
Spiked
pH = 6.22
Temp = 24
Ammonia pH
10.06
Without Spike
Sample 9
pH = 7.76
Temp = 25
Ammonia pH
9.99
Sample 10
Spiked
pH = 6.85
Temp = 24
Ammonia pH
10.06
[Ca2+]
EDTA (L)
Trial 1
Trial 2
Trial 3
Average
Trial 1
Trial 2
Trial 3
Average
Trial 1
Trial 2
Trial 3
Average
0.00334
0.00344
0.00349
0.003423333
0.0034
0.00329
0.00359
0.003426667
EDTA (L)
[Ca2+]
0.02804
0.02721
0.02828
0.027843333
Trial 1
Trial 2
Trial 3
Average
0.02685
0.02642
0.02632
0.02653
Ca 2+ ppm
1.619E-07
0.0064873
1.62E-07
0.0064936
Ca ppm
2+
1.317E-06
0.052764
1.254E-06
0.0502752
[Ca2+]
EDTA (L)
Ca 2+ ppm
Trial 1
Trial 2
Trial 3
Average
0.00022
0.00052
0.00038
0.000373333
1.621E-09
6.498E-05
Trial 1
Trial 2
Trial 3
Average
0.00032
0.00028
0.00059
0.000396667
1.723E-09
6.904E-05
[Ca2+]
EDTA (L)
Trial 1 (rough)
Trial 2
Trial 3
Trial 4
Trial 5
Average
0.0213
0.01961
0.01999
0.01992
0.0198
0.01983
0.0008069
[Ca2+]
EDTA (L)
Trial 1 (rough)
Trial 2
Trial 3
Trial 4
Average
Ca 2+ ppm
0.0058
0.00534
0.00528
0.00537
0.00533
32.339644
Ca 2+ ppm
2.315E-08
0.0009278
Calculations:
[EDTA] =
[Ca2+] =
M CaCO3 ∗L CaCO3
L EDTA
[CaCO3 ]×VCaCO3
VWater
=
=
0.01M∗0.003L
0.02949L
= 0.0010173M
(0.0013592 M)×0.03 L
0.025 L
= 0.00163 M
Ca2+ ppm = 40078 X [Ca2+] = 40078 X 0.00163 = 65.37 ppm
95% CI = x ±
t×s
√n
= 59.92 ±
3.182 × 0.165
√3
= [60.332, 59.511]
known value−experimental value
)×
known value
% error = (
45.7−59.92114
)×
45.7
100% = (
100% = 31.1%
Results:
1 - Well U
2 - Well T
3 - Brockie U
4 - Brockie T
5 - creek
6 - Dasani
7 - Figi
8 - Aquafina
9- Fountain
10 - Acadia
Experimental
59.92114
53.07198
33.6715
0.015445
0.070805
0.006494
0.050275
6.9E-05
32.33965
0.000899
Sample
Source
1
Well water
untreated
Well water
treated
Brockie Commons
water untreated
Brockie Commons
water treated
Tyler Run water
2
3
4
5
6
7
8
9
10
Known
45.7
6.12
20.3
0.6902
0.02
0
18
0
20.3
20.3
Experimental
mean
59.921
Reported
value
45.7
%
error
31.1
53.072
6.12
767.2
33.672
20.3
65.9
0.0154
0.6902
97.8
0.0708
0.02
254
Dasani bottled
water
Figi bottled water
0.00649
0
NA
0.0503
18
99.7
Aquafina bottled
water
Campbell Hall
fountain water
Acadia bottled
water
0.000069
0
NA
32.340
20.3
59.3
0.000899
20.3
100
95% CI
[60.332,
59.511]
[52.880,
52.264]
[37.674,
29.669]
[0.147,
-0.116]
[0.555,
-0.414]
[0.384,
-0.371]
[0.750,
-0.649]
[0.419,
-0.419]
[32.753,
31.926]
[0.536,
-0.534]
Relationship to
reported value
Lower
Lower
Lower
Higher
Within
Within
Higher
Within
Lower
Higher
Conclusions:
The concentration of [Ca2+] was determined for multiple water samples, and from this the
hardness of the water (ppm) was calculated. Experimentation seemed to go reasonably well. The main
problem with this lab was that reported known values may not have all been valid or applicable.
Manufacturers of Dasani and Aquafina did not report values online, and a phone call to customer service
proved fruitless. Determining the reported concentration of untreated well water was also difficult, as
little was known about the well sample. For treated water types, the Brita water filter was said to
remove 96% of impurities. This was used for both treated water types. Obviously the blanket reported
values did not fit the results, and more time should have been set aside to obtain individual reported
values. There was adequate time for experimentation, but seeking out reported values had not been
foreseen to take as much time and effort as it did.