Experimental Chemistry I
Experimental Chemistry I CHEM 111
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This 0 page Class Notes was uploaded by Herta Weber on Sunday November 1, 2015. The Class Notes belongs to CHEM 111 at Pennsylvania State University taught by Staff in Fall. Since its upload, it has received 37 views. For similar materials see /class/233161/chem-111-pennsylvania-state-university in Chemistry at Pennsylvania State University.
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Date Created: 11/01/15
nlexandra Salt October 20 20 I 0 The Ghemitlry of natural lllaleu Ghem I I I l05 Parlnem Zachary Ryan Savannah Salina Sohaylano ami Tn nndreul mama Saltz 1 Introduc on Water hardness is die amount of soluble cations lat are present in a given source of water given in terms of Calcium Carbonate l The USGS states that two ofthe most important chemical species CaZTand Mng which come from mineral dissolution is what causes water hardness along wi l o ler divalent cations2 Dissolution is die dissolving or breaking up of parts 3 It is essential for plants and animals There are many other cations such as sodium potassium iron and aluminum mat are present in natural water samples but calcium and magnesium are signi cant to re water quality 1 Table 1 below describes die concentration levels of CaCOg calcium carbonate and how it effects die hardness of re water Table 1 General Guidelines of Water Hardness to more In general ifthere is a large concentration of Ca and Mg ien the water is said to be hard and if iere are lower concentrations ien it is considered to be soft The high concentrations of these ions are unsuitable for many household and industrial uses Most soaps are anionic surfaceactive agents lat work by reducing le surface tension of water and weakening the chemical bonds 1 The divalent cations react wi l soap anions to form insoluble soap scum and mineral deposits mat may form when heated 5 When hard water is heated rocklike deposits form on the surface of pipes boiler walls tubes and evaporator surfaces This narrows pipes causes blockages and is extremely expensive to remove l The harder the water is the bigger the problem gets for industries One of the simplest me lods of nding out what solutes are present would be to evaporate re water sample and examine le nonvolatile solid mat remains This is called die total dissolved solids TDS of le water sample 1 There are several means in which one can determine the hardness of their water Two common ones used are E lylenediaminetetraacetic acid EDTA titrations and die other is Atomic Absorption Spectrophotometry AA EDTA is aversatile chelating combining agent which is a substance whose molecules can form several bonds to single metal ions 6 EDTA titration involves a series of reactions and is able to form soluble complexes wi l calcium and magnesium ions 1 An indicator Eriochrome Black T which is red when it complexes is added then EDTA is added drop wise to the sample until die sample turns blue which means that all die metal ions have been released from the sample 7 This indicator is water soluble and is intensely colored because of le delocalized electrons in the structure 1 When die solution turns blue the EDTA forms a complex with the calcium or magnesium ions leaving the indicator Eriochrome Black T uncomplexed 6 The reaction below is showing me visible reaction that is seen by le EDTA titrations HDZ39 Mg CazTMgD39 I Ca2EDTA CaEDTAigIgEDTAJr HD391 Blue Red Blue Atoms in die electronic ground state can absorb photons at waveleng ls corresponding to the energy change from le ground to excited states 8 In order for the atom to be excited le energy of die light falling on le atoms must match die energy separation between die two electronic levels 1 This is shown in Figure 1 below Figure 1 Atomic electronic energy levels involved wi l absorption 1 Saltz 2 as I s E2 hVAE 39 N AEE2E1 As seen in Figure 1 absorption will occur the energy of the incident hv AB 1 AA instruments measure this absorption of light in the excited state such as that of calcium and magnesium 9 The amount of absorbance is proportional to the concentration of the metal atoms in the water sample 1 Figure 2 AA Instrument A outside View and B inside View 1 Monochmmcler housing Lump hun ing oxidan fun 1 mg ml metal alums rrom sampl In region 1 there are hallow cathode lamps which emit the monochromatic light that corresponds to the given AE of the element being tested from the water sample The voltage excites the magnesium or calcium ions inside the lamp When the atoms relax a monochromatic light is produced which is equal to the energy separation of the two electronic levels shown in Figure 3 1 Figure 3 Atomic electronic levels involved with relaxation l E2 139 MWAEE2E1 I a a I E1 Region 2 of Figure 2 uses the sample chamber and burner which provides the temperature ame The light from the hallow cathode lamp passes through the ame where the water sample is atomized Light will only be absorbed if there is a matching energy separation of the electronic energy levels Region 3 contains three components The grating is adjusted so that only the light produced by the excited state is able to pass through the monochrometer The AA sample is aspirated into the burner by placing the aspirator into the water sample The light absorbance value will show up on the screen A plot of absorbance versus concentration which is known as Beer s Law Aabc where a as a constant that depends on the substance absorbing light b is the Saltz 3 path leng l and c is die concentration produces a linear relationship this is called a calibration curve that can be used to compare the absorbance data from re water sample 1 There is a subtle difference between drese two ways of determining water hardness EDTA reacts with all divalent cations while AA is speci c to the ion being tested for Two techniques are used to solve for water hardness in order to insure drat results obtained are accurate Softening techniques are used to make the water manageable There are many softening techniques such as chemical water softeners water filters mechanical water softeners and magnetic water conditioners 10 EDTA reactions can be used to soften water Calcium chelates will remove any trace irons or copper ions that promote die spoilage ofoils 1 A common method of removing die divalent cations from water samples is by ion exchange Cation Exchange Resins are polymers primarily used for purifying water 11 The resin contains usually Na or HT cations that can bind to die Ca2 and Mng releasing die sodium into die sample This is usually carried out by saturating the water irough a column containing die ion exchange material 1 This works because the polymers beads are actually open meaning drat the solution can ow irough le crosslinked polymer bringing it into a close proximity wi l the exchange resin 12 The water tested was taken from iree different locations in State College Pennsylvania and one from a Brita Filter System which was filled wi l Penn State water One is from on le Penn State Campus from le six l oor Ritner Hall showers The o ler two are from apartments 524 Locust Lane State College and 1520 Chaumont Avenue State College near Lemont Penn State s water sources come from rivers lakes streams ponds reservoirs springs and wells There are two main mountains around Penn State die Tussey Mountain and die Nimny Mountain As water travels over surfaces of land or irough the ground it dissolves naturally occurring minerals such as calcium and magnesium 13 The samples from State College should be rather hard because of die nearness to the mountains Looking at atopographical map to determine how mountainous an area is Chaumont Avenue was extremely at all around in Locust Lane was a little bit hillier man Chaumont and Ritner Hall which is located near Bigler Avenue and Pollock Road is very hilly 14 The higher the elevation die more water there is to dissolve minerals 13 Therefore Chaumont Avenue will have soft water Locust Lane will have sligh y hard water while Ritner Hall will have very hard water Since the water from le Brita Filter is from Penn State which is mountainous then it will have very hard water too but since it is going irough a filtration it should be less hard than die Ritner Hall water Filters are a softening technique used ierefore it should be softer 10 Procedure Taken from Chemtrek 1 1 Dilute re water sample for AA to 11 ratio this was a deviation from Chemtrek dris was added by le instructions of die Teaching Assistant This was done only if re water was taken from Penn State because it is harder therefore harder for die light source to go irough the sample The water sample is to be diluted to 201 if from le ocean water due to die high concentrations of salt in the water Obtain two extralarge pipets and cut off die stems Fill die bulbs wi l the diluted water sample about two lirds of die way full Place drem in a 24 well tray for easy transportation When at die AA machine place the aspirator into the sample zero it out and wait for le system to level off Record le number the absorbance wavelength This will be done twice one that detects die calcium cations and die o ler mat detects die magnesium cations 2 Set up a hot plate for Total Dissolved Solids test TDS Obtain a small piece of aluminum foil and place one drop ofdistilled water one drop of1 x 10393 M Ca2 and one drop of le water Saltz 4 sample Allow for it all to evaporate leaving behind just die undissolved solids The known concentration is die reference for re amount of solids left behind 3 Add 1 drop of NH3 NH4C1 MgEDTA buffer to a 1 X 12 well tray Add one drop of ie undiluted water sample to each well one drop of re 1 X 10393 M Ca2solution and add one drop of die EBT indicator to each well Add 1 drop of1 X 10394 M EDTA to re first well 2 to the second 3 to die lird and so on When re color change occurred the cations are fully saturated and marked die concentration of the water sample One deviation from Chemtrek was at if a color change did not occur in die 12 wells men it needed to be continued out into ano rer 1 X 12 well tray till die titration was complete This will determine die CaZTin solution by using die equation below 4 Repeat re steps from part iree but also add one drop of re 1 X 10393 M Mg2solution This will be used to determine the concentration of die Mng and CaZTin solution by using the equation below MEDTAVEDTA MCaZTVtotalNorN MEDTAVEDTA MMgZTand CaZTVtotal 5 Add some of the water sample can use diluted water sample if wanted but one must remember to multiply die concentration by two dris is a deviation from Chemtrek to a vial and add 20 mg of Arm n Hammer Sodium Bicarbonate to re vial and shake well Use re EDTA titration from step 4 determine die concentration of die softened solution using the equation above 6 Transfer a small amount of cation exchange resin into avial Add some of re water sample to die vial Diluted water sample can be used if wanted but one must remember to multiply die concentration by two dris is a deviation from Chemtrek Shake gen y or about a minute then let seme Remove all of the supernatant liquids by using a clean microburet Be careful not to suck up re resin beads Test it for die pH and ien do die titration from step 4 to determine re concentration of the softened water using re equation above Results Concentration Equation MEDTAVEDTA MCaZTVtotal MEDTAVEDTA MMgZTand CaZTVtotal This is used to calculate die initial concentrations of die calcium and magnesium in the water that was obtained irough die EDTA titrations 1 Molarity to PPM Equation 1 X 10 3 moles Cat Og 1000 g Cat Og 1000 mg CaCog 1Lofsolution X lmole Cat Og X lgCaL 03 quotThis equation is used to convert the initial concentrations obtained in EDTA from Molarity moles solute Liters solution to ppm Parts per Million 1 Converting PPM Ca and Mg to CaC03 X ppm Ca2 X 25 25x ppm CaCO3 X ppm MgZTX 412 412X ppm CaCO3 100ppm Once die concentrations of calcium and magnesium have been converted to ppm iey men need to get put into terms of CaCOg This is done by multiplying die ppm of calcium by 25 and multiplying die ppm of magnesium by 412 These are ien added toge rer to get die total concentration involved with re total water hardness Table 2 Calcium Check Standard Table Table 3 Check Table 001714 002725 015647 024874 065244 AA Standard Chart Ca2 AA Standard Chart Mg2 A08 E A 506 E g m g 04 T a E 02 g E 3 E 0 0 10 20 30 40 lt quot39 y 08199 009500 20 00 3O 00 4O 00 50 00 60 00 y 021x 0019 Mg Concentration ppm R2 0996 Ca concentration ppm R2 0997 Table 5 Comparison of EDTA and AA Table 4 Calcium and Magnesium Contn39butionto Hardness Table am T L gquot L 39 39 l f AA Ca2 Hard Total Hardness sulfa 6 Ca2 ppm ness As CaCO3 ppm with 39 mquot CaCo A ppm 1 Floor L 3478 24992 6248 Dilution factor of 11 Ritner Hal 117445 Shower 15 Brita 3602 5197 3544 3084 25699 28000 2 Filtration AA Mg Hardness S t Mg2 ppm As CaCos ys em ppm 16 524 Locust 5724 4280 4658 2008 18973 18000 Lane 17 3093 13341 5497 1520 0049 Less 0182 Less Less 12000 Chaumont than 1 than 1 than 1 used Avenue 10393 M 18 Call Saltz Table 6 Comparison of Different Techniques Table 7 Comparison of TDS Table Method Total Difference Hardness CaCO 3 ppm Water Source 1 Description Versus Reference Reference A slight milky white ling 6th Floor Ritner Hall A solid milky white Table 8 Comparison of Water Softening Shower 15 nng mob darker Techniques than the reference Brita Filtration A solid milky white Vamr Ann N Ion pH after System 16 ling muchrdarker Source Hammer Exchange treated than the reference Solution Resin with the 524 LocuSt Lane A SO d milky White ppm ppm Ion 17 ng With SPeCkS 0f Exchange SO da slightly Resin darker than the 639 Floor reference Ritner Ha11 1520 Chaumont A milky white ring Shower Avenue 18 not much darker 15 than the reference Brita 16000 10000 3 Filtration System 16 524 Locust 18000 4000 Not Lane 17 provided 1 520 Using the Using the Not Chaumont 1 x 10 M 1 x 104M provided Avenue Caz Ca2 18 8000 8000 Discussion The rst test that was done was me total dissolved solids test TDS The samples of each water source were compared to the reference of le known concentration of calcium It was sligh y milky white ring mat was a lime bit darker man that of distilled water The water from 6m Floor Ritner Hall Shower 15 was a solid milky white ring mat was much darker than the reference Brita Filtration System 16 was a solid milky white ring iat was much darker than me reference as well The one big difference between lese two was iat le water substance from the Saltz 7 Ritner Hall Shower had more of a solid circle more man just a solid ring 524 Locust Lane 17 was a solid milky white ring wi l some solid subsmnce in it but was only a lit e bit darker man mat of die reference and die water sample from 1520 Chaumont Avenue 18 was a milky white ring mat was not much darker man die reference Results from le lab showed mat the Brim lter had die hardest water according to AA It had a concentration of 257ppm ranking it as very hard water due to the fact that it is over 180 ppm 16 In le hypo lesis it was predicted mat die Brim filter would have softer water man mat of le Ritner shower According to die makers of Brita lters it is said that die filters are designed to remove some of the concentrations of calcium and magnesium in die water 19 The one ling mat may deviate lis comment from le results gomen from AA is that die filter may not have been changed in a while merefore not reducing the concentration of magnesium and calcium from the water The 639h oor Ritner shower had a concentration of235 ppm and was also considered very hard 15 This was right on wi l die prediction of die hypo le sis which stated mat it would be hard because of le higher elevation ofPenn Smte versus the other sources being tested The water sample from 524 Locust Lane was still considered very hard at 190 ppm 17 The hypo lesis stated iat it would have sligh y hard water so lis was a shocking result Due to die topographical map Locust Lane did not have a very mounminous area around it 14 One ling mat may not have been mken into account is the amount of sewage mat die area has The waste from Wastewater Treatment Plants WW TPs can add hardness 20 The water sample from 1520 Chaumont Avenue had soft water The result ofAA was less than 1 ppm 18 The hypo lesis said mat die water would be soft but mere was still hesimtion mat it would be mat soft The location is close to many different filtering water lines widlin five miles 13 The EDTA results were rather different The 639h Ritner Hall showers according to EDTA titrations had die hardest water It was very hard at 300 ppm This was about 65 ppm harder than die AA value 15 The Brim filter had die neXt hardest water still very hard water at 280 ppm 16 and men was the water from 524 Locust Lane as hard water 180 ppm 17 The water from 1520 Chaumont Avenue was too hard to do the EDTA titration mat die test was done with le known concentration of Ca2 The result was slightly hard at 120 ppm 18 but still was die softest of die water samples like predicted in le hypo lesis The results from EDTA matched le hypo lesis a bit closer wi l the Brim filtered water being sligh y softer man mat of the 6 h oor Ritner Hall showers Each of the EDTA titration values had a different value man die AA The shower water altered about 65 ppm in favor of die AAbeing lower The Brim filter was opposite it differed about 23 ppm in favor of die EDTA results being lower while die water sample from 524 Locust Lane only differed about 10 ppm EDTA picks up on all divalent cations while AA only shows die concentration of the specific ions being tested 1 Therefore the results from le AA should be more accurate There are many sources involved with EDTA titrations that can affect le accuracy of the results When titrating if the drops put in are not all relative ly die same size it can affect which well one would see the color change Air bubbles in die pipets can also affect whe ler die drop went direc y to the well or if some dispersed around it Even trying to keep count of die drops in die wells can get hard and could affect the results While wi l AA it is mainly done irough a machine and set to a specific element Machines are never 100 accurate but have been tested and fur ier improved to be more accurate Based on the Check Smnd Graphs Figures 4 and 5 we know iat there is a slight deviation of die actual results of AAbut still very minor There is a low amount of sensitivity wi l le AA machines while wi l EDTA each person mat does it brings a new level of accuracy and precision to it Therefore it is really sensitive of a technique One thing wrong affects die whole thing Saltz 8 The water softening techniques affected each water sample in a different way Overall die Ion Exchange Resin was more effective at softening die water The Arm N Hammer Sodium Bicarbonate replaced a lot of die Ca2 and MgZT ions wi l NaT while die ion exchange resin replaced it wi i HT The 63911 Floor Ritner Hall Shower was softened to 220 ppm from the Arm N Hammer and was softened to 10 ppm with the Ion Exchange Resin 15 The Brita Filter System s water softened to 160 ppm with the Arm N Hammer and went down to 100 ppm with the Ion Exchange Resin 16 The water sample from 524 Locust Lane softened to 180 ppm with the Arm N Hammer and softened to 40 ppm with the Ion Exchange Resin 17 With The water sample from Chaumont Avenue being too soft the known concentration of calcium was used 1 x 10393M Ca2 It softened to 80 ppm from both the Ion Exchange Resin and Arm N Hammer Conclusion In conclusion water hardness is determined by le concentrations of magnesium and calcium cations in the water The higher die concentration the harder the water Three tests were done one mat just quali ed die results called TDS and two mat quanti ed the results AA and EDTA titrations All of lis goes into die final mlly of which water sample is die hardest Based on le collection ofresults of le AA EDTA titration and the TDS die obvious water sample that was the most hard was the water from le 639h Floor Ritner Hall showers It showed a high concentration of both calcium and magnesium and show from le smrt of die experiment mat it had the most solids in it The next hardest substance was die water from le Brim Filtration system but it was not mat far behind mat of Ritner Hall Then was die water sample of 524 Locust Lane which had smaller AA and EDTA values but seemed a little off with le TDS description There was a small amount of solid with le ring which made it seem like mere was an error in technique wi l die hot plate The softest of die water samples by far was mat of 1520 Chaumont Avenue wi l values for everything less man 1 ppm A majority agreed wi l die initial theory of die hypothesis wi l minor alterations as le results of die experiment were collected One alteration was die softening mat die Brim Filtration System should have done to the water from Penn Smte Brim Filter surprisingly did not really affect die hardness of die water The one reason that mis may have not occurred is the fact that die Brim Systems only temporarily soften the water It is also not nearly as powerful as that of reverse osmosis or distillation 19 Its power is limited The water from the apartment locations was very different from one another One was really hard while die other was soft Based on the topographical map le results did not seem like they would differ mat dramatically from one ano ler Usually when living in a house or apartment there is agreater need for die owners to keep die water quality as high as it can It improves die quality of everything and definitely reduces die amount of harm and soap scum to the appliances in the house In lis case le water from 524 Locust Lane was still considered to be very hard References 1 Thompson S PS U Cbemtrc39k SmalkS39cac EchH39ments for General Chemistry 17 h ed PrenticeHall Englewood Cliffs NJ 2011 pp 101 to 1022 and 34 2 USGS WaterQuality Information Water Hardness and Alkalinity hgngwaterusg govowgghardnessalkalinightml accessed October 202010 Saltz 9 Webswr s NeWDI39ctionary and Thesaurus Wiley Publishing Cleveland Ohio 2002 pp 182 Water Quality Bulletin Explanation of Water Hardness htm accessed October 20 2010 Brown T LeMay H Bursten B Murphy C Woodward P Chemistry The Central Science 1139h ed PrenticeHall Upper Saddle River NJ 2009 pp 788 Spurlock D Determination of Water Hardness ByComplexometric Titration Class Notes April 10 2009 t quot ins edquot DSPURLOC C121 weekm htm accessed November 4 2010 Gannon University Determination of Water Hardness by EDTA Titration http vvvv Harmon Pdquot resource dep sim new chemexp les Most20used o20ChemLa o20Files H o20wate o20hardness df accessed October 26 2010 Atomic Absorption AA and Emission AE Spectrometry February 2 2007 http vvvv mm Pdquot 201 chem201 AA AE labpdf accessed October 27 2010 Alexander C Atomic Absorption Spectroscopy Tap Water Analysis November 18 2008 http vvvv r sns 39 quot uLUUfaIli IThome students chem31 SampleFonnal Labpdf accessed November 2 2010 Water Treatment Me rods hgpqgwwwhardwatenorggwater treatmenthtml accessed October 5 2010 Webster s Online Dictionary De ne Ion Exchange hgpwwwwebstersonline 1 I 39A39 rmo wm 39 http WW Frwa nru39wntPrl39mrrlne dictionary H qLprartnerpub 0939450753529744203Av0gd01tdlgampcofFORIDZo3A9ampieUTF 8ampgIonZo20ExchangeampsaSearch0 accessed November 6 2010 Ion Exchange Resins hmnzicognzChemProcessesWaterg13Dpdf accessed November 4 2010 SCBWA Water Quality Report WWWscbwaog accessed October 20 2010 Trailscom State College Topo Graph http vvvv trails a hxppanerrOFtrueSzz18ampe259769404927185ampn4519754 88170951amps50ampsizesampsgledrg r accessed October 25 2010 Alexandra Saltz s Notebook pp 2631 Zachary Ryan s Notebook pp 3639 Savannah Salinas Notebook pp 3033 SohaylaRostami s Notebook pp 3236 Brita FAQS Britahttp WWWbritanetukfaqs htmlDL15 accessed November 9 2010 Saltz 10 20 Murphy S General Information on Hardness Basinh pgbcnbouldercousbasingdatgg SEngnfogHardhtml accessed November 9 2010
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