undergone different stages of filtration process so using this kind of water

Undergone different stages of filtration process so

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undergone different stages of filtration process, so using this kind of water would not form any complex ions when titrated with EDTA. RESULTS AND DISCUSSION Upon preparation of stock EDTA solution, MgCl 2 6H 2 O crystals were added to the dissolved salt EDTA. The fact that Mg-EDTA has a higher formation constant hence a higher tendency to form complexes than Ca- EDTA, Mg 2+ from EDTA solution can easily displace Ca 2+ ions and form Mg-EDTA complex. Since Ca-EDTA has a lower K f , formation constant, Ca-EDTA is less stable because there is a greater energy for the complex to form, so adding more Mg 2+ ions will make the endpoint sharper. On the other hand, EDTA is essentially insoluble in water, and will only dissolve when pH is neutralized to 8. Addition of base, in this experiment NaOH pellets, facilitates dissolution of acid form of EDTA. Carbonate error can cause discrepancy in pH reading so adding HCl while dissolving CaCO 3 during the solution preparation is important for all reactions between metal ions and EDTA are pH dependent, and for divalent ions, solutions must be kept basic (and buffered) for the reaction to go to completion [6]. Most ligands are basic and bind to H + ions throughout a wide range of pH. Some of these H + ions are frequently displaced from the ligands (chelating agents) by the metal during chelate formation,so buffer was used to hold the pH constant. In this experiment, NH 3- NH 4 Cl buffer was used since EBT indicator only works when the pH is at 8 to 10, whereas the buffer has a pH equal to 10 [7]. The concentration of the two most common hard water ions, Ca 2+ and Mg 2+ was determined by titrating the water sample with a known chelating agent, ethylenediaminetetraacetic acid (EDTA). It was standardized with CaCO 3 thrice and the resulting average concentration of EDTA is 0.0069 M. During standardization, purple color appeared upon addition of EBT indicator compared to the expected wine red color of the solution. This may happen since there are no Mg 2+ ions in the solution, and the indicator only exists as wine-red complex due to the magnesium ions. Viva! Mineralized water was titrated with the standardized EDTA. The starting color sample upon addition of EBT indicator was wine red due to the existence of Mg 2+ ions (3), and upon titrating with EDTA, the color gradually changes from wine red to clear blue, indication that the endpoint is reached, which occurs when Ca 2+ ions complexes with EDTA (1), the same time the Mg 2+ complexes with it (2) sequentially and the Mg-EBT complex breaks as illustrated in the equation. Table 2 below shows the titration data of Viva! Mineralized water with standardized EDTA. The computed average hardness from three trials is 125.23 ppm (see Appendix B for calculations) which can be classified as hard based from water hardness scale. Q- test was first conducted and all values are accepted. The standard deviation computed is 5.22 ppm while the relative standard deviation is 41. 68 ppt. The confidence limit was also computed with confidence level at 95% and the resulting interval is [112.27
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  • Fall '17
  • Sir Jaden Smith
  • Drinking water, Hard water, Calcium carbonate

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