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Lowther 1Diana LowtherCHEM 113Section: 0043/28/19State College’s Water Hardness: Dangerous or clean?Diana Lowther: CHEM 113William Lee, John Lausev, Amy MacfarlaneTA: Meike Peels
Lowther 2Introduction:`When one drinks from a water bottle, they usually do not question the cleanliness of the water because we have confidence it has been filtered enough. Before water is treated and allowed to be bottled, they often contain harsh metals like magnesium and calcium. The presenceof Ca2+ and Mg2+ is also recognized as something called water “hardness” (1). According to theNIH, soft water in terms of calcium and magnesium are 0-60 and 0-3.5 mg/L respectively(2). In this lab, we measured the presence of these ions in ppm. Water hardness is important because notonly can concentrated amounts of metallic ions be dangerous to drink, but crystals can form in pipes and boiler walls, making foundations weak, or blocking pipelines(1). Water hardness also indicates what water needs to be treated, if it is being used for drinking water. `The first form of indication we used in this lab was EDTA. In an EDTA titration, a red color appears to prove the presence of Magnesium ions, and then once the solution turns blue during titrations, that indicates the endpoint of reaction of both mg2+ andca2+. The second technique used to determine metal concentration is Atomics Absorption Spectrophotometry (AA). The sample is put into a flame, and a beam of light goes through the flame onto the detector, resulting in a measurement of light absorbed by the water sample. The beam of light’s wavelength corresponds to the metal that we were interested in. This indicates the concentration of the metal ions in the water of observation. AA utilizes Beer’s law that states there is a direct correlation between absorbance and concentration. In this experiment if the sample exceeded more than one absorbance unit, it was diluted to get a better light transmission in AA. In the AA portion of the lab, we obtained the values of transmittance, and then we used that value to calculate the concentrations ourselves. The natural water sample from the Park Apartment complex needed filtering because of all of the gravel and debris from the parking lot. Later, as
Lowther 3part of the lab, we used the softening technique of ion exchange using Cation Exchange Resin. The resins in the solution exchange monovalent cations with divalent cations, therefore removingthe harmful metallic ions such as Ca2+ and Mg2+, softening the water. Our group consisted of John L, William L, Amy M, and Diana L, and our water samples respectively were shower water from Runkle Hall, sink water from the Graduate apartment complex, shower water from 109 North Barnard Street, and snow from the basketball courts outside the Park apartment complex. My hypothesis regarding the relative hardness of each sample is that the snow from the basketball courts at the Park apartment complex will be the hardest. This is due to the expectation of it containing contents of runoff, but also the Chemtrek states that rainwater generally consists of dissolved gasses, pollutants, etc(1). Next, it would be