Determination of Water Hardness Essay

IntroductionIn this lab a heart and soul of six titrations be to be per make uped. Three of them go forth be done victimisation a know Ca2+ ter mination, (1.000 g CaCO3 /L root word) and three of them will be done using an un cognize termination obtained from the personal credit line fashion. The objective of this lab is to specialize the cruelness of piddle, using the data collected from each titration performed with the unfathomable exemplification. Since the abrasiveness of irrigate arises from the presence of alloy ions, we can determination disodium salt of EDTA and the indicator Eriochrome fateful T to determine the concentration of M 2+ ( Mg 2+ or Ca 2+) metal ion impurities. chemical principle or theory involved in this labTo determine waters hardness we will use a technique called a chelometric titration. When a neutral jettyecule or anion (lewis base) donates electron pairs and attaches itself to a metal ion center (a Lewis acid), the resulting cluster of atoms forms a hit ion called a daedal. When such complexes form the electron donating groups are called ligands. When ligands with more than one binding site form complexes with metal ions, we call this process chelation, where the ligand utilize is called a chelating agent. (lab manual) In this lab the chelating agent used is Na2EDTA. Our Indictor Eriochrome faint T, is a dye, and will form a bug complex in the presence of a metal cation. As EDTA solution is added to the solution, the metal ions will complex to the EDTA solution leaving the indicator solvated. The chemical equation, with the known calcium ion solution, looks as follows Where H2In represents the solvated indicator Erichrome Black T dye.H2In + Ca 2+ CaIn + 2H(blue) (pink)As EDTA is added to the solution, it grabs the Ca ions forward from the Erichrome Black T dye molecules to form a more stable complex. When solvated, and alone in the solution, the Erichrome Black T dye will produce a blue color it can be delineate by the equation belowEDTA 4 + CaIn + 2H H2In + CaEDTA 2(pink) (blue)Procedure or MethodFirst unionize your disodium EDTA solution by weighing out 0.7- 0.8 grams of Na2EDTA and terminate it in 500 mLs of deionized water. graze in a sealed container and shake vigorously. regularize the Na2EDTA solution using calcium ion stock solution tote up 10 mL of calcium solution to a flask, and add 30 mLs of deionized water. Add 3 mLs of ammonium ion ion chloride buffer under the fastball hood and stir. Add 4 drops of the Eriochrome Black T indicator dye, then measure with the disodim EDTA solution inside 15 mins.At the endpoint the color changes from pink to violet to blue within 3-5 seconds. Note the volume of Na2EDTA that was used delivered from the burret, and repeat the titration 2 more times. Obtain an uncharted region water stock solution from the stock room taking note of the unknown number, then titrate with the standardized disodium EDTA solution Mix 25 mLs of t he prepared water sample with 20 mLs of deionized water, then under the fume hood, add 3 mLs of ammonium chloride buffer and stir. Add 4 drops of the Eriochrome Black T indicator dye, then titrate with the disodim EDTA solution within 15 minutes Repeat the titration 2 more times, and calculate the hardness of the prepared water sample from each of the titrations.Observations and Calculations step of Na2EDTA solution Amount of Na2EDTA solution required to titrate calcium Ion solution required to titrate unknown piddle sample running play 1 25.0 mL15.7 mLTrail 2 23.8 mL14.9 mL streamlet 3 23.6 mL15.5 mLBecause EDTA chelates Ca 2+ ions in a one-to-one hoagie ratio we can calculate the moles present of Na2EDTA using the following formula(s)Trial 1Na2EDTA = 10.00 mL CaCO3 1.000 g CaCO3 1mol CaCO3 1mol Na2EDTA25.0 mL Na2EDTA 1 L CaCO3 100.1g CaCO3 1 mol CaCO3 =.004 moles Na2EDTATrial 2Na2EDTA = 10.00 mL CaCO3 1.000 g CaCO3 1mol CaCO3 1mol Na2EDTA23.8 mL Na2EDTA 1 L CaCO3 100.1g Ca CO3 1 mol CaCO3 =.004197 moles Na2EDTATrial 3Na2EDTA = 10.00mL CaCO3 1.000 g CaCO3 1mol CaCO3 1mol Na2EDTA23.6 mL Na2EDTA 1 L CaCO3 100.1g CaCO3 1mol CaCO3 =.004233 moles Na2EDTAMean of all 3 trials = .004 + .004197 + .004233 / 3 = .004143 inviolate deviation Estimated Precision(ppt)Trial 1 .004143 .004 = 1.43 x 10-4 .02229 X 1000 = 23.09 ppt .004143 Trial 2 .004143 .004197 = -5.4 x 10-5Trial 3 .004143 .004233 = -9 x 10-5H2O hardness CalculatedTrial 1 15.7 mL Na2EDTA X .004143mol Na2EDTA X 1mol CaCO3 X 100.1g CaCO30.02500 L CaCO3 1L Na2EDTA 1mol Na2EDTA 1mol CaCO3Trial 1 H2O hardness = 260.44 ppmTrial 2 14.9 mL Na2EDTA X .004143mol Na2EDTA X 1mol CaCO3 X 100.1g CaCO30.02500 L CaCO3 1L Na2EDTA 1mol Na2EDTA 1mol CaCO3Trial 2 H2O hardness = 247.17 ppmTrial 1 15.5 mL Na2EDTA X .004143mol Na2EDTA X 1mol CaCO3 X 100.1g CaCO30.02500 L CaCO3 1L Na2EDTA 1mol Na2EDTA 1mol CaCO3Trial 3 H2O hardness = 257.12 ppmAverage H2O hardness for unknown 127 = 254.91 ppmConclusionThe average water hardness for unknown 127 is 254.91 ppm. metropolis of Gilberts average water hardness in 2011 was in the kitchen range of 41- 330 ppm (http//www.3mwater.com/medi/documents/ WaterReport_GilbertAZ.pdf). This is a large range but is a range that my unknown water sample would fall within. According to Fairfax Water, a look on over 180 ppm is considered very hard, and fit to the lab manual water with more than cc ppm is considered hard. Based on this information I would argue that my unknown water sample has a amply amount of metal ions present.ReferencesLab ManualCity of Gilbert, http//www.3mwater.com/medi/documents/WaterReport_GilbertAZ.pdfFairFax Water, http//www.fcwa.org/water/hardness.htm