determination of magnesium by edta titration calculations determination of magnesium by edta titration calculations

Before the equivalence point, Cd2+ is present in excess and pCd is determined by the concentration of unreacted Cd2+. Determination of Hardness of Water by EDTA Titration method - ReadCivil h`. Determination of Permanent hardness Take 100 ml of sample hard water in 250 ml beaker. First, we calculate the concentration of CdY2. Download determination of magnesium reaction file, open it with the free trial version of the stoichiometry calculator. Titrating with EDTA using murexide or Eriochrome Blue Black R as the indicator gives the concentration of Ca2+. Although neither the EDTA titrant nor its calcium and magnesium complexes are col-ored, the end point of the titration can be visually detected by adding a metallochromic indicator to the water sample. Although many quantitative applications of complexation titrimetry have been replaced by other analytical methods, a few important applications continue to be relevant. (Assume the moles of EDTA are equal to the moles of MgCO3) Chemistry Reactions in Solution Titration Calculations. Menu. 2. h? An analysis done on a series of samples with known concentrations is utilized to build a calibration curve. Calculate the Aluminum hydroxide and Magnesium hydroxide content in grams in the total diluted sample. where Kf is a pH-dependent conditional formation constant. (% w / w) = Volume. CJ OJ QJ ^J aJ hLS CJ OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ h- CJ OJ QJ ^J aJ t v 0 6 F H J L N ` b B C k l m n o r #hH hH >*CJ OJ QJ ^J aJ hH CJ OJ QJ ^J aJ hk hH CJ OJ QJ ^J aJ h% CJ OJ QJ ^J aJ hLS h% CJ OJ QJ ^J aJ hLS CJ OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ hp CJ OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ $ 1 4  |n||||]]||n| h, h% CJ OJ QJ ^J aJ hLS CJ OJ QJ ^J aJ hp CJ OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ hk hk CJ OJ QJ ^J aJ h% CJ OJ QJ ^J aJ #h hH CJ H*OJ QJ ^J aJ hH CJ OJ QJ ^J aJ #hH hH >*CJ OJ QJ ^J aJ &h hH >*CJ H*OJ QJ ^J aJ !o | } Thus one simply needs to determine the area under the curve of the unknown and use the calibration curve to find the unknown concentration. This means that the same concentration of eluent is always pumped through the column. The Titration After the magnesium ions have been precipitated out of the hard water by the addition of NaOH (aq) to form white Mg(OH) 2(s), the remaining Ca 2+ ions in solution are titrated with EDTA solution.. PDF EDTA Titration Calculations - Community College of Rhode Island The resulting spectrophotometric titration curve is shown in Figure 9.31a. ), The primary standard of Ca2+ has a concentration of, \[\dfrac{0.4071\textrm{ g CaCO}_3}{\textrm{0.5000 L}}\times\dfrac{\textrm{1 mol Ca}^{2+}}{100.09\textrm{ g CaCO}_3}=8.135\times10^{-3}\textrm{ M Ca}^{2+}\], \[8.135\times10^{-3}\textrm{ M Ca}^{2+}\times0.05000\textrm{ L Ca}^{2+} = 4.068\times10^{-4}\textrm{ mol Ca}^{2+}\], which means that 4.068104 moles of EDTA are used in the titration. \[\textrm{MIn}^{n-}+\textrm Y^{4-}\rightarrow\textrm{MY}^{2-}+\textrm{In}^{m-}\]. The solution was diluted to 500 ml, and 50 ml was pipetted and heated to boiling with 2.5 ml of 5% ammonium oxalate solution. Endpoints in the titration are detected using. This shows that the mineral water sample had a relatively high. h`. Report the molar concentration of EDTA in the titrant. Compare your results with Figure 9.28 and comment on the effect of pH and of NH3 on the titration of Cd2+ with EDTA. Transfer a 10.00-mL aliquot of sample to a titration flask, adjust the pH with 1-M NaOH until the pH is about 10 (pH paper or meter) and add . 23 0 obj<>stream The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. 243 26 In a titration to establish the concentration of a metal ion, the EDTA that is added combines quantitatively with the cation to form the complex. One way to calculate the result is shown: Mass of. +h;- h% 5CJ OJ QJ ^J aJ mHsHhs CJ OJ QJ ^J aJ h, CJ OJ QJ ^J aJ #hs h% CJ H*OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ h, h% CJ OJ QJ ^J aJ hk h% CJ OJ QJ ^J aJ &h, h% 5CJ H*OJ QJ ^J aJ &h, h% 5CJ H*OJ QJ ^J aJ #h, h% 5CJ OJ QJ ^J aJ h, 5CJ OJ QJ ^J aJ v x F  n o d 7$ 8$ H$ ^`gd Here the concentration of Cd2+ is controlled by the dissociation of the Cd2+EDTA complex. \[\mathrm{\dfrac{1.524\times10^{-3}\;mol\;Ni}{50.00\;mL}\times250.0\;mL\times\dfrac{58.69\;g\;Ni}{mol\;Ni}=0.4472\;g\;Ni}\], \[\mathrm{\dfrac{0.4472\;g\;Ni}{0.7176\;g\;sample}\times100=62.32\%\;w/w\;Ni}\], \[\mathrm{\dfrac{5.42\times10^{-4}\;mol\;Fe}{50.00\;mL}\times250.0\;mL\times\dfrac{55.847\;g\;Fe}{mol\;Fe}=0.151\;g\;Fe}\], \[\mathrm{\dfrac{0.151\;g\;Fe}{0.7176\;g\;sample}\times100=21.0\%\;w/w\;Fe}\], \[\mathrm{\dfrac{4.58\times10^{-4}\;mol\;Cr}{50.00\;mL}\times250.0\;mL\times\dfrac{51.996\;g\;Cr}{mol\;Cr}=0.119\;g\;Cr}\], \[\mathrm{\dfrac{0.119\;g\;Cr}{0.7176\;g\;sample}\times100=16.6\%\;w/w\;Fe}\]. 0 To calculate magnesium solution concentration use EBAS - stoichiometry calculator. the solutions used in here are diluted. Add 4 drops of Eriochrome Black T to the solution. Complexation Titration - Chemistry LibreTexts PDF Titration of Chloride - YSI EDTA (mol / L) 1 mol Magnesium. This is equivalent to 1 gram of CaCO 3 in 10 6 grams of sample. Titration Calculator An important limitation when using an indicator is that we must be able to see the indicators change in color at the end point. If there is Ca or Mg hardness the solution turns wine red. Determination of Calcium-Magnesium Hardness of Water - Construction How Conditions to the right of the dashed line, where Mg2+ precipitates as Mg(OH)2, are not analytically useful for a complexation titration. In an acid-base titration, the titrant is a strong base or a strong acid, and the analyte is an acid or a base, respectively. The first method is calculation based method and the second method is titration method using EDTA. H|W$WL-_ |`J+l$gFI&m}}oaQfl%/|}8vP)DV|{*{H [1)3udN{L8IC 6V ;2q!ZqRSs9& yqQi.l{TtnMIrW:r9u$ +G>I"vVu/|;G k-`Jl_Yv]:Ip,Ab*}xqd e9:3x{HT8| KR[@@ZKRS1llq=AE![3 !pb Dilutes with 100 ml of water and titrate the liberated iodine with 0.1M sodium thiosulphate using 0.5ml of starch solution, added towards the end of the titration, as an indicator. MgSO4 Mg2++SO42- Experimental: h, CJ H*OJ QJ ^J aJ mHsH(h Determination of Hardness: Hardness is expressed as mg/L CaCO 3. &=\dfrac{(5.00\times10^{-3}\textrm{ M})(\textrm{50.0 mL}) - (\textrm{0.0100 M})(\textrm{5.0 mL})}{\textrm{50.0 mL + 5.0 mL}}=3.64\times10^{-3}\textrm{ M} We can account for the effect of an auxiliary complexing agent, such as NH3, in the same way we accounted for the effect of pH. Calcium and Magnesium Determinations by EDTA Titrations First, however, we discuss the selection and standardization of complexation titrants. PDF Determination of Calcium by Titration with EDTA - College of Charleston Calcium is determined at pH 12 where magnesium is quantitatively precipitated as the hydroxide and will not react with EDTA. In this method buffer solution is used for attain suitable condition i.e pH level above 9 for the titration. &=\dfrac{\textrm{(0.0100 M)(30.0 mL)} - (5.00\times10^{-3}\textrm{ M})(\textrm{50.0 mL})}{\textrm{50.0 mL + 30.0 mL}}\\ The method adopted for the Ca-mg analysis is the complexometric titration. 0000002034 00000 n It is sometimes termed as volumetric analysis as measurements of volume play a vital role. We will use this approach when learning how to sketch a complexometric titration curve. Both magnesium and calcium can be easily determined by EDTA titration in the pH 10 against Eriochrome Black T. If the sample solution initially contains also other metal ions, one should first remove or mask them, as EDTA react easily with most of the cations (with the exception of alkali metals). %%EOF trailer 5 22. This dye-stuff tends to polymerize in strongly acidic solutions to a red brown product, and hence the indicator is generally used in EDTA titration with solutions having pH greater than 6.5. As shown in the following example, we can easily extended this calculation to complexation reactions using other titrants. \[\begin{align} The solution was then made alkaline by ammonium hydroxide. U! A buffer solution is prepared for maintaining the pH of about 10. The other three methods consisted of direct titrations (d) of mangesium with EDTA to the EBT endpoint after calcium had been removed. In the lab 1 ppm CaCO 3 is expressed as 1 mg CaCO 3 per 1 Liter of sample or ppm is mg CaCO . Most indicators for complexation titrations are organic dyesknown as metallochromic indicatorsthat form stable complexes with metal ions. Complexometric determination of calcium - Titration and titrimetric methods 6ADIDnu1cGM?froF%a,;on_Qw!"eEA#z@$\Xx0f 80BUGc77 b`Y]TkEZt0Yu}5A\vm5Fvh5A/VbgvZd Calculations. PDF EXPERIMENT - 1 Estimation of Hardness of Water by EDTA Method 0000001481 00000 n 0000002921 00000 n It can be determined using complexometric titration with the complexing agent EDTA. As is the case with acidbase titrations, we estimate the equivalence point of a complexation titration using an experimental end point. HWM6W- ~jgvuR(J0$FC*$8c HJ9b\I_~wfLJlduPl PDF EDTA Titrations 1: Standardization of EDTA and Analysis of Zinc in a 0000011407 00000 n to the EDTA titration method for the determination of total hardness, based on your past experience with the ETDA method (e.g., in CH 321.) 0000002676 00000 n The intensely colored Cu(NH3)42+ complex obscures the indicators color, making an accurate determination of the end point difficult. Calculate the number of grams of pure calcium carbonate required to prepare a 100.0 mL standard calcium solution that would require ~35 mL of 0.01 M EDTA for titration of a 10.00 mL aliquot: g CaCO 3 = M EDTA x 0.035L x 1 mol CaCO 3/1 mol EDTA x MM CaCO 3 x 100.0mL/10.00mL 3. For a titration using EDTA, the stoichiometry is always 1:1. In the section we review the general application of complexation titrimetry with an emphasis on applications from the analysis of water and wastewater. Table 9.13 and Figure 9.28 show additional results for this titration. Transfer magnesium solution to Erlenmeyer flask. The experimental approach is essentially identical to that described earlier for an acidbase titration, to which you may refer. The third titration uses, \[\mathrm{\dfrac{0.05831\;mol\;EDTA}{L}\times0.05000\;L\;EDTA=2.916\times10^{-3}\;mol\;EDTA}\], of which 1.524103 mol are used to titrate Ni and 5.42104 mol are used to titrate Fe. PDF ESTIMATION OF HARDNESS OF WATER BY EDTA METHOD - University of Babylon If the sample does not contain any Mg2+ as a source of hardness, then the titrations end point is poorly defined, leading to inaccurate and imprecise results. EDTAwait!a!few!seconds!before!adding!the!next!drop.!! In the method described here, the titrant is a mixture of EDTA and two indicators. Even if a suitable indicator does not exist, it is often possible to complete an EDTA titration by introducing a small amount of a secondary metalEDTA complex, if the secondary metal ion forms a stronger complex with the indicator and a weaker complex with EDTA than the analyte. Neither titration includes an auxiliary complexing agent. For example, as shown in Figure 9.35, we can determine the concentration of a two metal ions if there is a difference between the absorbance of the two metal-ligand complexes. A complexometric titration method is proposed to determine magnesium oxide in flyash blended cement. For example, an NH4+/NH3 buffer includes NH3, which forms several stable Cd2+NH3 complexes. \[K_\textrm f''=\dfrac{[\mathrm{CdY^{2-}}]}{C_\textrm{Cd}C_\textrm{EDTA}}=\dfrac{3.33\times10^{-3}-x}{(x)(x)}= 9.5\times10^{14}\], \[x=C_\textrm{Cd}=1.9\times10^{-9}\textrm{ M}\]. It is widely used in the pharmaceutical industry to determine the metal concentration in drugs. 3 22. A more recent method is the titration of magnesium solution with ethylene-diamine tetra-acetate(Carr and Frank, 1956). This leaves 8.50104 mol of EDTA to react with Cu and Cr. Titration . Magnesium levels in drinking water in the US. This can be done by raising the pH to 12, which precipitates the magnesium as its hydroxide: Mg2+ + 2OH- Mg(OH) 2 The sample is acidified to a pH of 2.33.8 and diphenylcarbazone, which forms a colored complex with excess Hg2+, serves as the indicator. It is vital for the development of bones and teeth. Complexometric Titration - EDTA, Types of Complexometric Titration - BYJUS Standardize against pure zinc (Bunker Hill 99.9985%) if high purity magnesium is not available. Volume required to neutralise EDTA. Determining Calcium Ion Concentration in Water Chemistry Tutorial 2) You've got some . The consumption should be about 5 - 15 ml. Unfortunately, because the indicator is a weak acid, the color of the uncomplexed indicator also changes with pH. startxref Introduction: Hardness in water is due to the presence of dissolved salts of calcium and magnesium. EDTA (mol / L) 1 mol Calcium. A 0.1557-g sample is dissolved in water, any sulfate present is precipitated as BaSO4 by adding Ba(NO3)2. The molarity of EDTA in the titrant is, \[\mathrm{\dfrac{4.068\times10^{-4}\;mol\;EDTA}{0.04263\;L\;EDTA} = 9.543\times10^{-3}\;M\;EDTA}\]. The description here is based on Method 2340C as published in Standard Methods for the Examination of Water and Wastewater, 20th Ed., American Public Health Association: Washington, D. C., 1998. h, 5>*CJ H*OJ QJ ^J aJ mHsH.h 3: Hardness (in mg/L as CaCO 3 . 1. \end{align}\], To calculate the concentration of free Cd2+ we use equation 9.13, \[[\mathrm{Cd^{2+}}] = \alpha_\mathrm{Cd^{2+}} \times C_\textrm{Cd} = (0.0881)(3.64\times10^{-4}\textrm{ M})=3.21\times10^{-4}\textrm{ M}\], \[\textrm{pCd}=-\log[\mathrm{Cd^{2+}}]=-\log(3.21\times10^{-4}) = 3.49\]. 0 2 4 seWEeee #hLS h% CJ H*OJ QJ ^J aJ hLS CJ OJ QJ ^J aJ hp CJ OJ QJ ^J aJ h`. Solution for Calculate the % Copper in the alloy using the average titration vallue. \end{align}\], \[\begin{align} See the text for additional details. Next, we draw our axes, placing pCd on the y-axis and the titrants volume on the x-axis. The solution is warmed to 40 degrees C and titrated against EDTA taken in the burette. A red to blue end point is possible if we maintain the titrands pH in the range 8.511. Background Calcium is an important element for our body. %PDF-1.4 % Preparation of 0.025M MgSO4.7H2O: Dissolve 0.616 grams of analytic grade magnesium sulfate into a 100 mL volumetric flask. 0000000016 00000 n At a pH of 3 the CaY2 complex is too weak to successfully titrate. Because EDTA forms a stronger complex with Cd2+ it will displace NH3, but the stability of the Cd2+EDTA complex decreases. EDTA Titration Calculations The hardness of water is due in part to the presence of Ca2+ ions in water. which means the sample contains 1.524103 mol Ni. Solving equation 9.13 for [Cd2+] and substituting into equation 9.12 gives, \[K_\textrm f' =K_\textrm f \times \alpha_{\textrm Y^{4-}} = \dfrac{[\mathrm{CdY^{2-}}]}{\alpha_\mathrm{Cd^{2+}}C_\textrm{Cd}C_\textrm{EDTA}}\], Because the concentration of NH3 in a buffer is essentially constant, we can rewrite this equation, \[K_\textrm f''=K_\textrm f\times\alpha_\mathrm{Y^{4-}}\times\alpha_\mathrm{Cd^{2+}}=\dfrac{[\mathrm{CdY^{2-}}]}{C_\textrm{Cd}C_\textrm{EDTA}}\tag{9.14}\]. General chemistry 1 analytic report - Experiment 9 DETERMINATION OF Analytical Methods for Magnesium - SAGE Journals Standardization of EDTA: 20 mL of the standard magnesium sulfate solution is pipetted out into a 250 mL Erlenmeyer flask and diluted to 100 mL . Standard magnesium solution, 0.05 M. Dissolve 1.216 g of high purity mag- nesium (Belmont 99.8%) in 200 ml of 20% hydrochloric acid and dilute to 11. The resulting metalligand complex, in which EDTA forms a cage-like structure around the metal ion (Figure 9.26b), is very stable. At the equivalence point we know that moles EDTA = moles Cd2 + MEDTA VEDTA = MCd VCd Substituting in known values, we find that it requires Veq = VEDTA = MCdVCd MEDTA = (5.00 10 3 M)(50.0 mL) 0.0100 M = 25.0 mL Dilute 20ml of the sample in Erlenmeyer flask to 40ml by adding 20ml of distilled water. Next, we draw a straight line through each pair of points, extending the line through the vertical line representing the equivalence points volume (Figure 9.29d). Titre Vol of EDTA to Neutralise (mls) 1 21. Determination of hardness of water by EDTA method At the beginning of the titration the absorbance is at a maximum. PDF Zinc-EDTA Titration - University of California, Irvine Estimation of Calcium (Titrimetric Method) - BrainKart 5CJ OJ QJ ^J aJ #h`. Now that we know something about EDTAs chemical properties, we are ready to evaluate its usefulness as a titrant. Figure 9.32 End point for the titration of hardness with EDTA using calmagite as an indicator; the indicator is: (a) red prior to the end point due to the presence of the Mg2+indicator complex; (b) purple at the titrations end point; and (c) blue after the end point due to the presence of uncomplexed indicator. Dilute to about 100mL with distilled water. 4. 0000001090 00000 n hbbe`b``3i~0 Hardness is reported as mg CaCO3/L. EDTA (L) Molarity. We can solve for the equilibrium concentration of CCd using Kf and then calculate [Cd2+] using Cd2+. PDF Determination of Calcium and Magnesium in Water - Xylem Analytics Solving gives [Cd2+] = 4.71016 M and a pCd of 15.33. The actual number of coordination sites depends on the size of the metal ion, however, all metalEDTA complexes have a 1:1 stoichiometry. ! Prepare a standard solution of magnesium sulfate and titrate it against the given EDTA solution using Eriochrome Black T as the indicator. In addition, EDTA must compete with NH3 for the Cd2+. 4 Sample Calculations (Cont.) 1ml of 0.1N potassium permanganate is equivalent to 0.2 mg of calcium Therefore, X3 ml of' Y' N potassium permanganate is equivalent to. All Answers (10) 1) Be sure the pH is less than 10, preferably about 9.5-9.7. 8. T! Water Hardness (EDTA) Titration Calculations Example - YouTube 0000023545 00000 n Magnesium ions form a less stable EDTA complex compared to calcium ions but a more stable indicator complex hence a small amount of Mg2+ or Mg-EDTA complex is added to the reaction mixture during the titration of Ca2+ with EDTA. 0000023793 00000 n 13.1) react with EDTA in . Titration 2: moles Ni + moles Fe = moles EDTA, Titration 3: moles Ni + moles Fe + moles Cr + moles Cu = moles EDTA, We can use the first titration to determine the moles of Ni in our 50.00-mL portion of the dissolved alloy. For each of the three titrations, therefore, we can easily equate the moles of EDTA to the moles of metal ions that are titrated. The analogous result for a complexation titration shows the change in pM, where M is the metal ion, as a function of the volume of EDTA. 0000002349 00000 n ! Click n=CV button above EDTA 4+ in the input frame, enter volume and concentration of the titrant used. Calculation of EDTA titration results is always easy, as EDTA reacts with all metal ions in 1:1 ratio: That means number of moles of magnesium is exactly that of number of moles of EDTA used. To evaluate the relationship between a titrations equivalence point and its end point, we need to construct only a reasonable approximation of the exact titration curve. 0000009473 00000 n From Table 9.10 and Table 9.11 we find that Y4 is 0.35 at a pH of 10, and that Cd2+ is 0.0881 when the concentration of NH3 is 0.0100 M. Using these values, the conditional formation constant is, \[K_\textrm f''=K_\textrm f \times \alpha_\mathrm{Y^{4-}}\times\alpha_\mathrm{Cd^{2+}}=(2.9\times10^{16})(0.37)(0.0881)=9.5\times10^{14}\], Because Kf is so large, we can treat the titration reaction, \[\textrm{Cd}^{2+}(aq)+\textrm Y^{4-}(aq)\rightarrow \textrm{CdY}^{2-}(aq)\]. teacher harriet voice shawne jackson; least stressful physician assistant specialties; grandma's marathon elevation gain; describe key elements of partnership working with external organisations; leaving 4.58104 mol of EDTA to react with Cr. OJ QJ ^J ph p !h(5 h(5 B*OJ QJ ^J ph ' j h(5 h(5 B*OJ QJ ^J ph h(5 B*OJ QJ ^J ph $h(5 h(5 5B*OJ QJ ^J ph hk hH CJ OJ QJ ^J aJ hj CJ OJ QJ ^J aJ T! Report the concentration of Cl, in mg/L, in the aquifer. Add 4 drops of Eriochrome Black T to the solution. Click here to review your answer to this exercise. The hardness of a water source has important economic and environmental implications. Submit for analysis. Figure 9.29a shows the result of the first step in our sketch. Both analytes react with EDTA, but their conditional formation constants differ significantly. 2. This reagent can forms a stable complex with the alkaline earth metal like calcium ion and magnesium ion in alkaline condition pH above 9.0. %PDF-1.4 % The mean corrected titration volume was 12.25 mL (0.01225 L). dh 7$ 8$ H$ ^gd Erlenmeyer flask. The solution is titrated against the standardized EDTA solution. A spectrophotometric titration is a particularly useful approach for analyzing a mixture of analytes. In addition, the amount of Mg2+in an unknown magnesium sample was determined by titration of the solution with EDTA. In this section we will learn how to calculate a titration curve using the equilibrium calculations from Chapter 6. (b) Titration of a 50.0 mL mixture of 0.010 M Ca2+ and 0.010 M Ni2+ at a pH of 3 and a pH of 9 using 0.010 M EDTA. In this study Calcium can be precipitated as carbonate or oxalate, although presence of oxalates may make end point detection difficult. <<7daf3a9c17b9c14e9b00eea5d2c7d2c8>]>> Dissolve the salt completely using distilled or de-ionized water. EDTA, which is shown in Figure 9.26a in its fully deprotonated form, is a Lewis acid with six binding sitesfour negatively charged carboxylate groups and two tertiary amino groupsthat can donate six pairs of electrons to a metal ion. Estimation of Copper as Copper (1) thiocyanate Gravimetry, Estimation of Magnesium ions in water using EDTA, Organic conversion convert 1-propanol to 2-propanol. Log Kf for the ZnY2-complex is 16.5. hb``c``ie`a`p l@q.I7!$1)wP*Sy-+]Ku4y^TQP h Q2qq 8LJb2rO.dqukR Cp/N8XbS0X_.fhhbCKLg4o\4i uB The highest mean level of calci um was obtained in melon (22 0 mg/100g) followed by water leaf (173 mg/100g), then white beans (152 mg/100g . 21 0 obj <> endobj Suppose we need to analyze a mixture of Ni2+ and Ca2+. 0000020364 00000 n When the reaction between the analyte and titrant is complete, you can observe a change in the color of the solution or pH changes. \end{align}\]. In the determination of water hardness, ethylene-diaminetetraacetic acid (EDTA) is used as the titrant that complexes Ca2+ and Mg2+ ions. If MInn and Inm have different colors, then the change in color signals the end point.