Untitled Essay, Research Paper

The Chemistry of Natural Water INTRODUCTION The intent of this experiment is to research the hardness of the H2O on campus. Hard H2O has been a job for 100s of old ages. One of the earliest mentions to the hardness or softness of H2O is in Hippocrates discourse on H2O quality in Fifth century B.C. Hard H2O causes many jobs in both in the family and in the industrial universe. One of the largest jobs with difficult H2O is that it tends to go forth a residue when it evaporates. Aside from being aesthetically unpleasing to look at, the physique up of difficult H2O residue can ensue in the clogging of valves, drains and shrieking. This physique up is simply the accretion of the minerals dissolved in natural H2O and is normally called graduated table. Other than choke offing plumbing, the physique up of graduated table poses a big job in the industrial universe. Many things that are heated are frequently cooled by H2O running thru piping. The physique up of graduated table in these pipes can greatly cut down the sum of heat the chilling unit can pull off from the beginning it is seeking to heat. This poses a potentially unsafe state of affairs. The physique up of extra heat can make a batch of harm ; boilers can detonate, containers can run etc. On the impudent side of the coin, a physique up of graduated table on an object being heated, a boiler for illustration, can greatly cut down the heat efficiency of the boiler. Because of this, it takes much more energy to heat the boiler to the necessary temperature. In the industrial universe, this could amount to big amounts of money being thrown into otiose heat. In add-on to choke offing plumbing and cut downing warming efficiency, the physique up of difficult H2O besides adversely affects the efficiency of many soaps and cleansing agents. The ground for this is because difficult H2O contains many divalent or sometimes even polyvalent ions. These ions react with the soap and although they do non organize precipitates, they prevent the soap from making it & # 8217 ; s occupation. When the polyvalent ions react with the soap, they form an indissoluble soap trash. This is one time once more rather unpleasing to look at and discolorations many surfaces. The exclusive ground for all these jobs originating from difficult H2O is because difficult H2O tends to hold higher than normal concentrations of these minerals, and hence it leaves a considerable sum more residue than normal H2O. The concentration of these minerals is what is known as the H2O & # 8217 ; s Total Dissolved Solids or TDS for short. This is simply a manner of showing how many atoms are dissolved in H2O. The TDS vary from Waterss of different beginnings, nevertheless they are present in at least some measure in all H2O, unless it has been passed through a particular distillment filter. The comparative TDS is easy measured by puting two beads of H2O, one distilled and one experimental on a hot plate and vaporizing the two beads. You will detect that the experimental bead will go forth a white residue. This can be compared to samples from other beginnings, and can be used as a rough manner of mensurating the comparative TDS of H2O from a specific country. The more residue that is left behind, the more dissolved solids were present in that peculiar sample of H2O. The residue that is left, is in fact, the solids that were in the H2O. Another, possibly more quantitative manner of finding hardness of H2O is by ciphering the existent concentrations of bivalent ions held in solution. This can be done one of two ways. One is by serially titrating the H2O with increasing concentrations of index for Mg++ and Ca++ ( we will be utilizing EDTA ) . This will state us the approximative concentration of all bivalent ions. This method of consecutive titrations is accurate to within 10 parts per million ( ppm ) . Another possible method for finding the hardness of H2O is by utilizing Atomic Absorption Spectrophotometry or AA for short. AA is a method of finding the concentrations of single metallic ions dissolved in the H2O. This is accomplished by directing little sums of energy thru the H2O sample. This causes the negatrons to presume aroused provinces. When the negatrons bead back to their land provinces, they release a photon of energy. This photon is measured by a machine and matched up to the corresponding component with the same E as was released. This is in bend is related to the strength of the visible radiation emitted and the sum of light absorbed and based on these computations, a concentration value is assigned. A speedy overview of how the atomic soaking up spectrophotometer works follows. First, the H2O sample is sucked up. Then the H2O sample is atomized into a all right aerosol mist. This is in bend sprayed into an highly high strength fire of 2300 C which is attained by firing a precise mix of air and ethyne. This mixture burns hot plenty to atomise everything in the solution, dissolver and solute likewise. A visible radiation is emitted from a hollow cathode lamp. The visible radiation is so absorbed by the atoms and an soaking up spectrum is obtained. This is matched with cataloged known values to achieve a reading on concentration. Because there are so many jobs with difficult H2O, we decided that possibly the H2O on Penn State & # 8217 ; s campus should be examined. My spouses and I decided to prove degrees of divalent ions ( specifically Mg++ and Ca++ ) in consecutive floors of residence halls. We hypothesized that the upper degree residence halls would hold lower concentrations of these bivalent ions because seeing as how they are both heavy metals, they would be given to settle out of solution. The Ca++ should settle out foremost seeing how it is heavier than the Mg++ , but they will both lessening in concentration as they climb to higher floors in the residence halls. PROCEDURE We collected samples from around Hamilton Halls, West halls. In order to be systematic, we collected samples in the forenoon from the H2O fountains near the south terminal of the halls. We collected H2O samples from each floor in order for comparing. The ground we collected them in the forenoon was so that the Mg++ and Ca++ would be in noticeable measures. We so went about and tested and analyzed via consecutive titrations and via Atomic Absorption Spectrophotometry. We besides obtained a TDS sample simply for the interest of comparing, and to guarantee that were in fact dissolved solids in our H2O samples ( without which this lab would go moot ) . For the consecutive titration, we simply mixed the H2O sample with EBT, and so with increasing concentrations of EDTA. The EBT served as an index to state us when the concentrations of the EDTA and the bivalent ions in solution were equal ( really it told us when Mg++ was taken out of solution but that served the same intent ) . This allowed us to happen the concentration of the divalent ions diss

olved in solution. Based on this, we calculated the parts per million and the grains per gallon for each water sample. Finally, we took an AA reading for each sample. This gave us absorption values and concentration values for each of the two main metals we were observing; Ca++ and Mg++. We then plotted a graph of Atomic Absorption Standards. These were values given to us by the AA operator. These values helped us to calibrate the machine. The parts per million that we find will be based on plugging in the reported absorption value into the resulting curve from the graph of these values. The resulting concentration was used as the final value for the hardness for that particular sample. All calculations and conclusions were done based on these final values obtained for the concentration of Ca++ and Mg++. For more detail, refer to full in depth procedure as directed by: Penn State Version of… Chemtrek August 1996 – July 1997; Stephen Thompson; Prentice Hall; Englewood Cliffs, NJ 07632; ? 199 RESULTS Molarity x (100g CaCO3 / 1 mole CaCO3 ) x (1000 mg / 1g) = Xmg/1000g = ppm Grains/Gallon = ppm /17.1 Example: (1.6 x 10 -3 moles / 1 Liter) x (100g CaCO3 / 1 mole CaCO3 ) x (1000 mg / 1g) = 160 ppm 160 ppm/17.1 = 9.35 grains/gallon Serial Titration Results Name: # Molarity Parts Per Million Grains Per Gallon Samir Sandesara 1 1.6 x 10 -3 160 9.35 Andy 2 1.6 x 10 -3 160 9.35 Ben 3 1.2 x 10 -3 120 7.01 Tom 4 1.8 x 10 -3 180 10.5 Table #1: This table displays the values obtained by serial EDTA titration of the water samples. Conversion Factors Given by AA operator: Ca++ = 2.5 Mg++ = 4.2 Ca++ x 2.5 = CaCO3 hardness ppm value Mg++ x 100 x 4.5 = Mg CO3 hardness ppm value *NOTE: the Mg++ is x 100 because it was diluted before it was put into the AA. Example: Ca++: 27.52 x 2.5 = 68.8 ppm 4.02 g/gal Mg++: .251 x 100 x 4.2 = 105.42 6.16 g/gal Atomic Absorption Values Name : # Abs Mg++ Abs Ca++ AA ppm Mg++ AA ppm Ca++ ppm Mg++ ppm Ca++ g/Gal Mg++ g/Gal Ca++ Samir 1 0.2270 0.5923 0.251 27.52 105.42 68.8 6.16 4.02 Andy 2 0.2041 0.5493 0.225 25.10 92.40 62.75 5.40 3.67 Ben 3 0.3633 0.5800 0.401 26.83 168.22 67.07 9.88 3.90 Tom 4 0.2673 0.5589 0.295 25.65 123.90 64.11 7.24 3.75 Table #2: This table displays the values obtained from AA analyzation, and shows the hardness of the water as contributed by each individual element. Absorbency Values Parts Per Million 0.000 0.0 0.125 0.1 0.403 0.5 0.716 1.0 Absorbency Values Parts Per Million 0.0000 0.000 0.0142 0.493 0.0262 0.985 0.0536 1.970 0.2360 9.850 0.4540 19.700 0.9230 49.250 Floor Number Hardness (ppm) 1 174.3 2 159.1 3 235.5 4 188.0 DISCUSSION The final hardness values were obtained by graphing the AA Standards on the previous page and then plugging in the absorption values give by the AA (Table #2). This is the grey line that appears in both graphs. When this line was extended down from the point of intersection, it was able to read the ppm value at that point. The ppm value for both Ca++ and the Mg++ were then summed to attain the final hardness of the water. The other numbers above reveal much about the water in Hamilton Hall. Looking at the final hardness values that were attained, it is clear that the two upper floors had harder water than the lower floors. However, table #2 shows that the concentration of Ca++ decreased overall as the water climbed higher in the dormitory. What was unexpected was that the concentration of Mg++ actually increased as it climbed higher. As of present, I have no rational scientific explanation for this. The only possible explanation I could possibly think of is perhaps there is something within the plumbing that contains Mg and the further the water travels in it, the more dissolves of the Mg dissolves. Aside from that, there does not seem to be any possible explanation. What is also interesting is that with the exception of the #3 sample, the hardness values attained from the AA were very similar to those attained by serial EDTA titration. These indicates a low source of error and gives support to my numbers. Even more support is added to the numbers when the ppm values are added up in Table 2. These values, for the most part, also seem to be in a relatively tight “ball park” of the final AA values. Given that the accuracy of serial titrations is ? 10 ppm, it is extremely safe to say that my numbers are correct. A brief overview of the numbers seems to show that there is indeed a trend, and the more in-depth look at the numbers shows that they all seem to back each other up. This seems to imply a that most if not all of the results are quite accurate and precise. CONCLUSION Upon completion of this lab, it can be said that the data supports only half of the original hypothesis. Yes, the Ca++ did seem to decrease as the water got further from the source and climbed higher in the dormitories. However, the Mg++ did not. Instead it did quite the opposite and showed a general trend of increasing in concentration as it got further away from the source and higher in the dormitories. Perhaps a viable explanation could be attained if studies were done on the plumbing inside the building. Perhaps there is a high concentration of magnesium in the solder used to hold the pipes together. Perhaps it is not in the pipes but rather perhaps the people on the upper floors get up later and therefore at the time of collection, the water in the upper floors had been sitting longer than that on the lower floors. In either case,. More investigation would have to be conducted in order determine what caused the unexpected results. In light of this discrepancy, the overall accuracy of the lab was very good. The numbers all seem to back each other up and correlate very well. As was mentioned in the previous section, the precision and accuracy with which this lab was carried out seems to indicate that there is very little source of error. The only one that was possibly flawed was sample #3. This could have been due to an error in the dilution or any other factor. Since I personally did not carry out that portion of the experiment, I cannot be sure. However, the other 3 samples provide more than ample ammounts of accurate information. Overall, it seems that the lab was quite well done. The hypothesis would have to be revised and as of this point, without further investigation, it would have to be reformulated to say that only the Ca++ would decrease in concentration whereas the Mg++ would increase. REFERENCES 1) Brown, Theodore L. et al; Chemistry The central Science; Sixth Edition; Prentice Hall, Englewood Cliffs, NJ; ?1994 2) Stephen Thompson; Penn State Version of…Chemtrek; August 1996 – July 1997; Prentice Hall; Englewood Cliffs, NJ; ? 1990 3) Internet Resource; http://www.kinetico.com/hard.htm