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Dongho KimNov. 11th, 2013Chem 111-101TA : Kristi LiddellGroup Members :Rajan KonaiUrjita KheraParvaneh LarganiSam LappDongho Kim“How is our daily water looks like?”Dongho Kim Liddell Chem111-101Chem 111 Lab Report Due Date (11/11/13)“How is our daily water looks like?”<Introduction>In a daily life, we usually drink water without any worry from a sink of our houses since we believe that the water is clean and pure. We probably may know that our water is coming from pipelines from underground manufactured by a local water company. However, we don’t really consider how the water comes from and how clear the water is. In order to check our daily water’s purity, we can use a data of water hardness by having some experiments called EDTA and AA so that we can distinguish what kinds of water is clean and pure.When we hear the word ‘water hardness’, it doesn’t feel common word in our daily life and also it doesn’t really mean how hard the actual water is. The definition of ‘water hardness’ is the transferred value of Calcium Carbonate from stored amount of Calcium and Magnesium in natural water.1) The unit of this value is called ‘ppm’ which is parts per million. The water that we have been drunk from sink of kitchen or some public places, doesn’t really harmful enough to affect our health badly, but it is important to know that ‘water hardness’ shows us how much Calcium and Magnesium are contained in natural water. It means that if a water hardness had a more Calcium but fewer Magnesium, it would be really healthy for our bodies because it may leads us to prevent some circulatory or heart disease according to some research results.2) On the other hand, Magnesium doesn’t really affect to us in a good way as we know because it could occur dehydration phenomenon by absorbing much Magnesium such as sea water which has a lot of Magnesium than Calcium. Therefore, if the value of water hardness is high, it doesn’t really mean that the water is good water or not. That is the main reason why we need to check the water contains more Calcium and fewer Magnesium.To measure water hardness, there are two widely known ways to get those ingredients. Those are called ‘EDTA (Ethylenediaminetetraacetic Acid)’ Titration and ‘AA (Atomic Absorption Spectrophotometry)’. These two words sound really difficult and complicated, but these two methods are pretty interesting and amazing experiments to do. First of all, EDTA titration is an experiment to get value of water hardness (or Divalent Cation Concentration) of Calcium or Magnesium by using EDTA into a natural water sample with NH3/NH4 Buffer which is an aqueous solution that contains weak acid and conjugate base or weak base and conjugate acid with Ammonia and Ammonium and also EBT indicator. The other experiment, AA, is a specific way to measure the concentration of Calcium and Magnesium divalent ions by absorbing sample water and also burning it into the flame so that it could be measured by reflecting on the spectroscopy in the AA experiment. These two experiments are used in a same way but EDTA experiment also reacts with all divalent ions and not just Calcium and Magnesium.In order to compare hardness of water, there should be different water samples from different locations so that we could see which area has less or more minerals in the water. Thus, we have 5 different locations, a private apartment (off campus) and four different halls in PSU dormitories. Before having these experiments, the writer (my personal thoughts) believed that a private apartment which was the writer’s location might have less hardness than other locations since the location is private property, there might be less amount of transferring water which means less contact with limestone in pipelines from a local water company. There might be lots of pipelines and more amount of transferring water under the dormitories’ undergrounds which meant the water in the dormitories might contacts more limestone in the pipelines than the writer’s. <Procedure>Each group member started to have their own experiment with their own water sample from different locations. The locations of water samples should not be the same since the purpose of this experiment was based on the comparison of water hardness from different locations. According to the steps in PSU Chemtrek written by Stephen Thompson pages 10 – 15 to 10 – 223), each member of the group took their own sample and followed the steps from the Chemtrek.First of all, every member was provided with a little foil on their desks. They were asked to put their own water sample as few drops and also distilled water and Calcium Chloride. Then, they brought that foil to the hot plate burner and waited until all liquids were evaporated. This is a small experiment to see the differences between the liquids’ residues on the foil after evaporations.After the evaporations, each member started to have EDTA titration experiment to perform on each water sample as its original sample and after that they began to mix with softening agent. There were commercial conditioning products for mixing with the water samples and each member mixed with this product just a little bit with their own water. They were asked to put one drop of NH3/NH4/MgEDTA buffer and EBT indicator in their water samples and these were experienced with the 1*12 strip. At this experiment, every member must drop the products accumulatively in every well so that EDTA solutions were titrated. There should be some color changes by these drops in the 1*12 strip. When the color changed, each member were asked to record the number of well that was changed. The reason why he/she should record the number of well is that the number of EDTA drops in that well will be used in the equation of EDTA to determine the value of water paring with the EDTA titration experiment, AA experiment was pretty simple and easy to measure. Every member went to the specific laboratory that had two AA instruments to measure each value of Calcium and Magnesium of their own water samples. At first, each member was asked to put the absorbing pipe into his/her own water sample, and press measure button to measure the value of Calcium or Magnesium. This value could be measured by the aerosol in the water and the monochromatic light through the sample. Since the water sample was absorbed by the instrument, it went to the flame to make a light which was occurred the wavelength of the light. The light from the AA instrument began to measure the wavelength of light which is responded to an excited electron of metal and went to the Monochrometer to measure the amount of absorbance by using spectroscopy principle. The measurements from the AA instruments were also known as concentration of Calcium and Magnesium by the first two calibration lines that were created at the experiments. Every member recorded the concentrations on their own notes.<Results>The observations that our members got from their own foils at the beginning of this experiment were like:Figure 1: Difference between Water sample after evaporation.Off CampusEast DormWest DormSouth DormCenter DormWater SampleTwo concentric white cloudy & little bit thick ringsConcentrated in the middle of the sampleConcentric white rings and concentrated in the middleTwo concentric white ringsConcentrated in the middle but had a white ringDistilledEvaporatedEvaporatedEvaporatedEvaporatedEvaporatedCaCl2EvaporatedEvaporatedEvaporatedEvaporatedEvaporatedAccording to this table, every water sample had something residue on the foil but nothing left from the distilled and CaCl2. This phenomenon was lead us to expect that there were some amount of Calcium and Magnesium in our water sample which were distilled one.Figure 2: 1st calibration graph of Ca2+.Figure 3: 2nd Calibration graph of Mg2+These are the Calibration graphs that our class members got at the certain time. This was not a constant measurement; it could be changed a little bit.Figure 4: The value of Calcium and Magnesium from the AA.Absorbance Valueppm hardnessCa2+0.5586131.81 ppmMg2+0.3717115.51 ppmTotal Hardness247.32 ppmFrom the Calibration graphs that we got above, we could use the equation which is slope of the tangent line (y = 0.0101x + 0.0261) to solve the Ca2+ absorbance in terms of x:0.5586 = 0.0101x + 0.02610.5325 = 0.0101xX = 52.72 ppm of Ca2+This is not the final ppm value of Ca2+. We must multiply divalent cation Ca2+ times the ratio of the molar mass of CaCO3. So, the final ppm value would be:52.72ppm * (100g of CaCO3 / 1mole) / (40g of Ca2+ / 1mole) = 131.81 ppm hardness.It is same calculation principle for Magnesium absorbance. From the Calibration graphs that we got above, we could use the equation which is slope of the tangent line (y = 0.0127x + 0.0152) to solve the Ca2+ absorbance in terms of x:0.3717 = 0.0127x + 0.01520.3565 = 0.0127xX = 28.07 ppm of Mg2+We also need to multiply divalent cation Mg2+ times the ratio of the molar mass of CaCO3. So, the final ppm value would be:28.07 ppm * (100g CaCO3 / 1mole) / (24.3g of Mg2+ / 1mole) = 115.51 ppm hardness.Figure 5: Total hardness of water samples in different locations.Absorbance Valueppm hardnessCa2+0.360182.67 ppmMg2+0.258178.71 ppmEast Hall Total Hardness161.38 ppmCa2+0.423198.27 ppmMg2+0.3254100.52 ppmWest Hall Total Hardness198.79 ppmCa2+0.240353.02 ppmMg2+0.188556.16 ppm South Hall Total Hardness109.18 ppmCa2+0.335476.56 ppmMg2+0.253077.06 ppmCenter (Pollack) Hall Total Hardness153.62 ppmFigure 6: The value of Calcium and Magnesium from EDTA Titration.Drops of EDTAppm hardnessWater Sample11220ppmSoftened Sample8160ppmHow do we get the ppm hardness of EDTA Titration? We need to use an equation which is M1*V1 = M2*V2 to get the concentration of the divalent cations.2*10-4 * 11 drops = M2 * 1drop0.0002 * 11 = M2M2 = 0.0022 mol of CaCO3This is not the final value of EDTA ppm. We must multiply CaCO3 molar mass with the concentration of CaCO3 and convert it into mg unit of CaCO3:(0.0022 mol of CaCO3 / liter) * (100g CaCO3 / mol CaCO3) * (1000mg CaCO3 / 1g CaCO3) = 220 mg CaCO3 / liter.Since we know that the density of water is 1mg CaCO3 / 1000g water = 1ppm, we can calculate the ppm hardness which would be:( 220mg CaCO3 / 1000g water ) = 220 ppm hardness.One of the questions (Q6) in PSU Chemtrek, we need to calculate the hardness as grains per gallon. We can convert hardness to grains per gallon by using 17.1 ppm which is equal to 1 grain CaCO3 / gallon. Thus, the calculation would be:220 ppm * (1 grain per gallon / 17.1 ppm) = 12.86 grains per gallon.Figure 7: Total EDTA hardness of both water sample and softened sample.Drops EDTAppm hardnessEast HallWater Sample12240 ppmSoftened Sample7 (3:1)140 ppmWest HallWater Sample360 ppmSoftened Sample8160 ppmSouth HallWater Sample5100 ppmSoftened Sample5100 ppmCenter (Pollack) HallWater Sample10200 ppmSoftened Sample5100 ppmFigure 8: The differences between AA and EDTA.AA hardnessEDTA hardnessDifference betweenAA and EDTAOff Campus247.32 ppm220 ppm27.32East Hall161.38 ppm240 ppm-78.62West Hall198.79 ppm60 ppm138.79South Hall109.18 ppm100 ppm9.18Center (Pollack) Hall153.62 ppm200 ppm46.38<Discussion>To compare with the writer’s hypothesis and the results from the AA and EDTA experiments, his hypothesis was not that wrong since the hardness of water could be changed based on the geological issues and also taste of water. According to the data, every member had the experiments with their water samples which were brought by pretty much different area. There might be some geological height differences between each location surely6). When we look at the measurements of hardness of off campus and West hall, the values were pretty high located around 200 ppm which meant high hardness value5). Plus, the values from the South and Center halls were treated as moderately hard5). The water from the East hall was treated as hard hardness5). Therefore, there would be some water hardness differences between the geological issues. It could be harder or softer than each other. The data between AA and EDTA are pretty much different than we expected because the differences were pretty bigger than we thought. However, the off campus and South Hall values were not that bad enough to get accurate data since the difference between AA and EDTA were less than 20 ~ 30 ppm. Plus, we could realize that EDTA measured residue of sample, caused by evaporation. Generally EDTA was added when TDS is done unlike AA molecule, and EDTA measured only left over substances. Therefore, there should be different measurements between those two experiments.According to the Department of Health in North Dakota4), there might not affect the taste of water by reducing the Ca2+ and Mg2+, but it could be a little bit different by comparing the hardness between the hilly section and lower section. We could guess that Off Campus, West Hall, and East Hall could be hilly sections around this local area by comparing the water hardness and the residues on the foil at the beginning of the laboratory. When we looked at the Figure 1, most of residue came out with white rings and it usually concentrated in the middle. But there could be a little bit difference in thickness between five of them. When the residue from off campus was evaporated, it came out really thick white two rings compared to the others. It might mean that there would be more minerals (Ca2+ and Mg2+). On the other hand, the water samples from lower section, South and Center (Pollack) Halls, also came out with white ring residues (not that thick as off campus one), but it came out with lower AA hardness than other locations which meant Calcium and Magnesium might be contained little bit less than hilly section samples. Thus, it could also be interpreted as lower water hardness might affect taste of water theoretically.<Conclusions>From this experiment, I could have an opportunity to see and observe seriously when I use or drink water from my house or any public place. The water from the underground or the rain from the sky actually affects the hardness of water that we usually use in our daily life. According to the EDTA and AA experiments, the value (=hardness of water) could be changed to softened or also could be changed to hardened which meant there might be a little bit taste difference between underground water that not contacted with the air but rocks contained with minerals and the water from the ground. Since we realized that the softening agent products (such as Brita) by reducing the hardness of water, we could use it as much better tasty and healthier use personally.<References>USGS Water – Quality Information<, Stephen. PSU Chemtrek. Joseph T. Keiser, 2013 – 2014 version, pgs. 10 – 15 to 10 – 22.Department of Health, Ground of water, North Dakota (January 6th, 2013)< Classification< Hardness - Penn State Library<; ................
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