Complexometric Determination of Water Hardness Essay

AbstractThe pissing hardship for unknown water supply smack number 40 was determined. From the results of the two complexometric titrations, the water rigor of the unknown try on was projectd to be 250.9 ppm CaCO3, which agrees with the ranges of accep delay water abrasiveness in the metropolis of Phoenix and Tempe Arizona. IntroductionWhen rainfall picks up impurities from the soil, ions of sodium, magnesium, calcium, iron, and other surfaces are change state into the water. These impurities are what cause residues left on glassware from the reaction with the lash used for cleaning. Water hardness is from the metal ions with a +2 ailment or higher being dissolved into the rainfall. When reporting water hardness, it is report in units of mg CaCo3/L of out(a)come, or in ppm due to adept mg of solute having one millionth of the mass of a liter of water or dilute aqueous termination. It is reported using only CaCo3 because typically, atomic number 20 is the largest con tributor to the water hardness. The purpose of this experiment was to determine the concentration of metal ion impurities in an unknown sample of hard water by perform a complexometric titration with EDTA. The results were then compared to the expected range for municipal water hardness from multiple city websites. MethodsAll procedures from the CHM 152 Lab, Complexometric Determination of Water Hardness (1) were followed precisely. strange water sample 40 was mixed with approximately 20 ml of DI water, 3.0 ml of Ammonia/Ammonium Chloride (NH(aq) Buffer pH=10), and 4 drops of Eriochrome swarthy T indicator solution. It was then titrated with .004197 M EDTA, which was also made in the lab from 0.7582 g of , added to 500 mL of DI water, that was then standardized with a stock Calcium Ion Solution (CaCO(aq) 1.00g/1.00L) by titration. A total of 3 titration trials were fuckd to find the just groinarity of the EDTA, and the average water hardness of unknown water sample 40. Allmas s measurements were taken from a AND Balance, serial number 12321601 and all titrations were done using a KIMAX buret, 173. pipette measurements were taken from a 25mL Bel-Art, and 15mL Bel-Art pipet. The numerical techniques used in this experiment were, stoichiometry with gram bulwarkecule ratio for calculating the megabyte of the EDTA solution and water hardness and congress average absolute deviation in ppt to show how closely the results from the govern EDTA titration of each trial agree with each other. Data Analysis found on the experiment and deliberations, 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 trial n was calculated as follows .0.01000 L CaCO3 SolnTotal EDTA Delivered L1.000 g CaCO31 L CaCO3 Soln1 mol CaCO3100.1 g CaCO31 mol Na2EDTA1 m ol CaCO3=Molarity of running n The Average 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) hold 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 above calculation came out to be 14.45 ppt. With the expected range of precision being at nigh five parts per thousand, it has been observed that the molarity of the standard Disodium EDTA solution includes most obvious error. It seems that the observation of color change when Na2EDTA was titrated to the mixture of CaCO3, DI water, Eriochrome Black T, and ammonia/ammonium chloride was the most error prone. Not know ing when to stop titrating the EDTA solution, would wee-wee accounted for a misreading of measurement for the total volume of EDTA solution added to complete the titration, making the final molarity for that trial less 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 within 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. Complexometric Determination of Water Hardness, Procedures, Mesa Community 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. right of first publication 2013 3. City of Tempe Az website. https//www.tempe.gov/index.aspx?page=1289Hardness, accessed 9/8/2013. Copyright