“All public water systems are required to perform routine testing and to report the findings from those tests at least once a year.”(LAB) These tests range from the pH level of water to the conductivity of water. “In 2011 [the Tampa Water Department] took approximately 10,000 water samples and performed approximately 50,000 analysis of water.”(Tampa) “Owners of private wells are responsible for ensuring the safety of their own water.” (LAB) This can be a difficult process. If not performed correctly, it is possible for private well owners to miss chemicals and contamination in their water which could lead to health risks. A test not commonly performed on drinking water is water hardness. “Water hardness is not always included in drinking water analysis as having hard or soft water is not a serious threat to health. However, high mineral content can cause high levels of buildup in water pipes and pumps, and a lack of certain minerals could allow for corrosion of the pipes.” (LAB) This lab will test water samples found on the campus of the University of South Florida for pH levels as well as the water hardness.
PH will be tested using pH strips or a pH meter. Water hardness will be tested using titration. The chemical EDTA will be used in order to determine the level of water hardness ranging from soft to very hard. EDTA is used because it is a ligand. A ligand is a substance that binds to a metal ion. (2)
Using EDTA should determine how many Ca+ ions in parts per million are present in the water sample. Then using the following charts will determine the level of hardness of the water.(1)(Spurlock)
Obtain two water samples from the campus of the University of South Florida. Record the time and location the water sample was obtained from. Start by taking the pH of the sample. Using a pH strip, dip the strip into the water sample and remove it. Note the color change and compare it to the pH strip container. Match the color as closely as possible and record that pH level. Next obtain a pH meter. The pH meter needs to first be calibrated using buffers with a pH of 4, 7, and 10. After calibrated the pH meter test the pH of both the water samples. Next is the titration of EDTA in the water samples. In order to do this, obtain a sample of EDTA. 0.008M of EDTA is the desired amount to titrate into the sample of water. In order to get this molarity, use the formula Molarity =. The amount of liters needed to titrate will be 50mL. Therefore 0.008M= meaning the number of moles needed to EDTA are 0.0004 moles. Multiply this number by EDTA’s molecular weight (292.24g/mol) and that gives the amount of EDTA needed which is about 0.117g. Take this 0.117g and dissolve it in 0.5L of deionized water. This will be the solution that is titrated. Next take 0.025L of the sample water and pour it into a flask. Set up the titration using a buret. The sample water needs a dye in order for the titration to be visible to the naked eye. Therefore add 10-15 drops of Eriochrome Black-T indicator to the sample water in the flask. Stir around and watch the sample turn to a pink/red color. Now slowly open the valve of the buret in order to let the EDTA solution mix and titrate with the sample water. Watch very closely. Once the sample water changes from pink to blue stop adding EDTA solution. This means the titration has been reached. Record the initial and final amounts of the EDTA solution on the buret. Next use the following formula to determine the concentration of Ca2+ ions found in the water sample. (Spurlock)
After finding the concentration of Ca2+ ions use the following formula to determine the hardness of the water in parts per million.(Spurlock)
Repeat this titration two more times with the first sample and repeat it three times with the second water sample.
Water Sample One
Water Sample Two pH: 8.03 pH: 7.29
Water Sample One (ppm CaCO3)