Complexometric Determination of Water Hardness Essay

AbstractThe irrigate austereness for occult region weewee sample number 40 was catch outd. From the results of the two complexometric titrations, the water scratchiness of the unknown sample was measured to be 250.9 ppm CaCO3, which agrees with the ranges of acceptable water callosity in the urban center of Phoenix and Tempe Arizona. IntroductionWhen rainfall picks up impurities from the soil, ions of sodium, magnesium, calcium, iron, and separate metals are dissolved into the water. These impurities are what cause residues left on glassware from the reaction with the soap used for cleaning. pee hardness is from the metal ions with a +2 charge or higher creation dissolved into the rainfall. When inform water hardness, it is reported in units of mg CaCo3/L of solution, or in ppm due to one mg of solute having one millionth of the cud of a liter of water or dilute aqueous solution. It is reported employ only CaCo3 because typically, Calcium is the largest contributor to the water hardness. The purpose of this look into was to determine the parsimony of metal ion impurities in an unknown sample of hard water by performing a complexometric titration with EDTA. The results were therefore compared to the expected range for municipal water hardness from multiple city websites. MethodsAll procedures from the CHM 152 Lab, Complexometric Determination of body of water Hardness (1) were followed precisely. Unknown water sample 40 was mixed with almost 20 ml of DI water, 3.0 ml of Ammonia/Ammonium Chloride (NH(aq) Buffer pH=10), and 4 drops of Eriochrome Black T indicator solution. It was then titrated with .004197 M EDTA, which was alike made in the lab from 0.7582 g of , added to 500 mL of DI water, that was then modularized with a stock Calcium Ion declaration (CaCO(aq) 1.00g/1.00L) by titration. A total of 3 titration struggles were completed to find the intermediate molarity of the EDTA, and the average water hardness of unknown water sample 40. Allmass measurements were taken from a AND Balance, serial number 12321601 and all titrations were done apply a KIMAX buret, 173. Pipet measurements were taken from a 25mL Bel-Art, and 15mL Bel-Art pipet. The numerical techniques used in this experiment were, stoichiometry with mole ratio for calculating the molarity of the EDTA solution and water hardness and relative average inviolate deviation in ppt to award how closely the results from the Standardized EDTA titration of each political campaign agree with each other. info AnalysisBased on the experiment and calculations, the average calculated concentration of metal ion impurities (water hardness) in unknown sample number 40 from this experiment was 250.9 ppm. From table 1, the average molarity of the titrated was calculated to be 0.004197 M. Table 1The molarity of the EDTA solution for each visitation n was calculated as follows .0.01000 L CaCO3 SolnTotal EDTA Delivered L1.000 g CaCO31 L CaCO3 Soln1 mol CaCO3100.1 g C aCO31 mol Na2EDTA1 mol CaCO3=Molarity of Trial n The total Molarity of the EDTA solution was calculated as follows Average Molarity of EDTA Solution =Calculated molarity from each trialNumber of titration trials To determine how closely the results of each trial from the Standard Disodium EDTA titration (Table 1) agreed with each other, a relative average absolute deviation calculation was done. It was calculated as followsAbsolute deviation for trial n= Na2EDTA avg molarity-Total Na2EDTA Trial nabsolute deviations3Na2EDTA avg molarity1000=Estimated Prescision (ppt) The results of the supra calculation came out to be 14.45 ppt. With the expected range of precision being at most five parts per thousand, it has been observed that the molarity of the standard Disodium EDTA solution includes some obvious error. It seems that the observation of color change when Na2EDTA was titrated to the compartmentalisation of CaCO3, DI water, Eriochrome Black T, and ammonia/ammonium chloride was th e most error prone. Not subtile when to stop titrating the EDTA solution, would have accounted for a misreading of measurement for the total peck of EDTA solution added to complete the titration, making the final molarity for that trial little thanwhat was expected.Table 2Based on the molarity results from table 1 and the data from table 2, the average calculated water hardness of unknown water sample 40 was calculated to be 250.9 ppm CaCO3. The water hardness of unknown water sample 40 for each individual trial was calculated as follows=Total EDTA soln Delivered L0.02500 L CaCO3 soln0.004197 mol EDTA1 L EDTA soln1 mol CaCO31 mol EDTA100.1 g CaCO31 mol CaCO31000mg1.0 g Average Water Hardness (ppm)mg CaCO31 L CaCO3Interpretation of ResultsBased on the data, the calculated water hardness of the unknown sample number 40 (250.9 ppm), is inwardly range of the city of Phoenixs calculated range of 164-291 ppm (2) and the city of Tempes calculate range of 150-400 ppm (3). References1. C omplexometric Determination of Water Hardness, Procedures, Mesa corporation College CHM152LL website, http//www.physci.mc.maricopa.edu/Chemistry/CHM152/index.html, accessed 9/7/2013. 2. City of Phoenix website. http//phoenix.gov/waterservices/quality/index.html, accessed 9/8/2013. Copyright 2013 3. City of Tempe Az website. https//www.tempe.gov/index.aspx?page=1289Hardness, accessed 9/8/2013. Copyright