95% and the resulting interval is [112.27ppm, 138.19 ppm]. Table 2. Viva! Mineralized Water AnalysisTitration DataTrial 123Water50 mL50 mL50 mL24210Ca+ EDTACaEDTA5.0 10fKx2428Mg+ EDTAMgEDTA4.9 10fKx2+2-Mg+ HInMgIn +H -4-+2-2-32MgIn +Y+H OMgY+HIn+H O(-) ()redwineclear blue
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sampleFinal volof EDTA8.9 mL18.4mL27.2mLInitial volof EDTA0 mL8.9 mL18.4mLNet volEDTA8.9 mL9.5 mL8.8 mLTotalHardness122.93ppm131.21ppm121.55ppmThe total cation content of the water samplebased from label’s given Ca2+and Mg2+content was also computed by adding thetotal CaCO3ppm and total CaCO3ppm fromMgCO3is 192.57 ppm, which can beclassified as very hard water. Comparing thiswith respect to the data obtained from EDTAtitration, it claims to have a higher Ca2+andMg2+content when the computed totalhardness from complexometric titrationappears to be less. The large difference of the total hardness ofthe two may due to different errors aroseduring the titration or preparation of thesolution. The discrepancy may be caused byseveral factors. Overtitration of the sampleanalysis is the common source of error sincethe detection of blue endpoint is notdistinguishable to purple color. The delayedchange of color of the solution can also bethe cause of overtitration. It is also importantto note that the indicator used must besuitable for the type of titration, which in thisexperiment we used EBT since it selectivelybinds with the Mg2+ions. Neglect to addbuffer can also cause error in theconcentration of the standardized EDTA sinceit is very sensitive to pH change, so it is alsoimportant to note that proper selection ofkind of buffer based on each pH range, inwhich in this experiment, is at 10.Another titration was done to determine thehardness of tap water. Table 3 below showsthe titration data of the tap water titratedwith standardized EDTA and the computedaverage total hardness as CaCO3ppm is62.15 ppm which is classified as moderatelyhard based from table 1.Table 3. Tap Water Analysis Titration DataTrial 12Watersample50 mL50 mLFinal vol ofEDTA4.5 mL9.0 mLInitial vol ofEDTA0 mL4.5 mLNet volEDTA4.5 mL4.5 mLTotalHardness62. 15ppm62.15 ppmCompared to the commercial mineral water’stotal hardness, it is as half as much of it. Butdaily consumption of this kind of water is notadvisable because it may contain chloride (tokill germs) that can easily react with otherorganic materials, and other alkalinesubstance (to maintain pH and preventscorrosion of pipes).SUMMARY AND CONCLUSIONS The standardized EDTA resulted to a 0.0069M after titrating it thrice with primarystandard CaCO3. Viva! Mineralized water wasused as sample and has an initial Ca2+content of 54 ppm and Mg2+content with 14ppm. The water sample was titrated withstandardized EDTA using EBT indicator. Theselection of the indicator was based on therange of its pH which is 8 to 10. NH3-NH4Clbuffer with pH at 10 was used to maintainthe pH of the solution since EDTA is pHdependent. After three trials of titration, the
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