Determining the Hardness of Water Lab Report
Autor: Jannisthomas • October 4, 2018 • 977 Words (4 Pages) • 715 Views
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(0.000142+0.000053+0.000088)/3
---------------------------------------------------- x 1000 = 20.05 ppt
0.004704 M Na2EDTA
Once the molarity of the Na2EDTA solution was determined, the Na2EDTA solution was used to titrate the unknown water sample and the volume delivered was recorded (figure 2). After three titrations, the water hardness was determined with this equation
0.01340 L Na2EDTA[pic 21][pic 22]
0.004704 mol Na2EDTA
1 mol CaCO3[pic 23][pic 24]
100100 mg CaCO3
0.02500 L CaCO3[pic 25]
1.0 L Na2EDTA
1 mol Na2EDTA
1 mol CaCO3[pic 26]
= 252.4 ppm
After calculating the water hardness of all 3 trials and averaging them out, the unknown water sample had a water hardness of 252.4 ppm
Trial Number
Volume of Na2EDTA delivered (mL)
Na2EDTA concentration (M)
Absolute Deviation (M Na2EDTA)
1
21.90
0.004562
0.000142
2
21.00
0.004757
0.000053
3
23.05
0.004792
0.000088
Mean | Estimated precision (ppt)
0.004792
20.05
(Figure 1)
Trial number
Volume Na2EDTA delivered (mL)
Water Hardness (ppm)
1
13.45
253.3
2
13.40
252.4
3
13.35
251.4
Average Water Hardness (ppm)
252.4
(figure 2)
Conclusion
The water hardness of an unknown sample was found using complexometric titration of a previously prepared water sample and Eriochrome Black T as the indicator. The tests were the observation of the color change from pink to blue while a magnetic stirrer was on. The results were then used as a basis for the unknown water sample.
The water hardness of the unknown water sample was calculated out to be 252.4 ppm. This water hardness was found by recording the volume of Na2EDTA delivered to the known sample then using the given formula to determine the molarity of the solution. This was then used to determine the water hardness of the unknown water sample
Sources
Arizona Republic, issued Saturday, November 5, 2005, page 360, “Soft water not good for pool”
Arizona Republic, Issued Sunday, August 11, 1991, page 83, “Don’t let Dust, Dirt, take your backyard oasis by storm”
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