trailer At the beginning of the titration the absorbance is at a maximum. Figure 9.30 is essentially a two-variable ladder diagram. 243 0 obj <> endobj In the section we review the general application of complexation titrimetry with an emphasis on applications from the analysis of water and wastewater. The method adopted for the Ca-mg analysis is the complexometric titration. 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! The solution is titrated against the standardized EDTA solution. The solution was then made alkaline by ammonium hydroxide. 5 22. A more recent method is the titration of magnesium solution with ethylene-diamine tetra-acetate(Carr and Frank, 1956). Because the color of calmagites metalindicator complex is red, its use as a metallochromic indicator has a practical pH range of approximately 8.511 where the uncomplexed indicator, HIn2, has a blue color. Obtain a small volume of your unknown and make a 10x dilution of the unknown. One consequence of this is that the conditional formation constant for the metalindicator complex depends on the titrands pH. The mean corrected titration volume was 12.25 mL (0.01225 L). seems!to!proceed!slowly!near!the!equivalence!point,!after!each!addition!of! Hardness is mainly the combined constituent of both magnesium and calcium. Recall that an acidbase titration curve for a diprotic weak acid has a single end point if its two Ka values are not sufficiently different. h, 5>*CJ H*OJ QJ ^J aJ mHsH.h Liebigs titration of CN with Ag+ was successful because they form a single, stable complex of Ag(CN)2, giving a single, easily identified end point. Prepare a 0.05 M solution of the disodium salt. endstream endobj 244 0 obj <>/Metadata 80 0 R/Pages 79 0 R/StructTreeRoot 82 0 R/Type/Catalog/ViewerPreferences<>>> endobj 245 0 obj <>/ExtGState<>/Font<>/ProcSet[/PDF/Text]>>/Rotate 0/StructParents 0/TrimBox[0.0 0.0 595.276 841.89]/Type/Page>> endobj 246 0 obj <> endobj 247 0 obj <>stream A 0.4482-g sample of impure NaCN is titrated with 0.1018 M AgNO3, requiring 39.68 mL to reach the end point. \end{align}\], \[\begin{align} If MInn and Inm have different colors, then the change in color signals the end point. If the metalindicator complex is too weak, however, the end point occurs before we reach the equivalence point. (not!all!of . Because EDTA has many forms, when we prepare a solution of EDTA we know it total concentration, CEDTA, not the concentration of a specific form, such as Y4. Complexometric Determination of Magnesium using EDTA EDTA Procedure Ethylenediaminetetraacetic Acid Procedure Preparing a Standard EDTA Solution Reactions 1.Weighing by difference 0.9g of EDTA 2.Quantitatively transfer it to a 250 mL volumetric flask 3.Add a 2-3mL of amonia buffer (pH 10) Add 1 or 2 drops of the indicator solution. Figure 9.35 Spectrophotometric titration curve for the complexation titration of a mixture of two analytes. Although each method is unique, the following description of the determination of the hardness of water provides an instructive example of a typical procedure. xref (7) Titration. ! Although EDTA forms strong complexes with most metal ion, by carefully controlling the titrands pH we can analyze samples containing two or more analytes. 2 23. EDTA (L) Molarity. (Assume the moles of EDTA are equal to the moles of MgCO3) Chemistry Reactions in Solution Titration Calculations. In the determination of water hardness, ethylene-diaminetetraacetic acid (EDTA) is used as the titrant that complexes Ca2+ and Mg2+ ions. Click n=CV button above EDTA 4+ in the input frame, enter volume and concentration of the titrant used. ! Titanium dioxide is used in many cosmetic products. 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). Calcium can be precipitated as carbonate or oxalate, although presence of oxalates may make end point detection difficult. 0000021647 00000 n Percentage. Titration . <<36346646DDCF9348ABBBE0F376F142E7>]/Prev 138126/XRefStm 1156>> EBAS - equation balancer & stoichiometry calculator, Operating systems: XP, Vista, 7, 8, 10, 11, BPP Marcin Borkowskiul. A scout titration is performed to determine the approximate calcium content. [\mathrm{CdY^{2-}}]&=\dfrac{\textrm{initial moles Cd}^{2+}}{\textrm{total volume}}=\dfrac{M_\textrm{Cd}V_\textrm{Cd}}{V_\textrm{Cd}+V_\textrm{EDTA}}\\ One way to calculate the result is shown: Mass of. \[\textrm{MIn}^{n-}+\textrm Y^{4-}\rightarrow\textrm{MY}^{2-}+\textrm{In}^{m-}\]. 0 Because the calculation uses only [CdY2] and CEDTA, we can use Kf instead of Kf; thus, \[\dfrac{[\mathrm{CdY^{2-}}]}{[\mathrm{Cd^{2+}}]C_\textrm{EDTA}}=\alpha_\mathrm{Y^{4-}}\times K_\textrm f\], \[\dfrac{3.13\times10^{-3}\textrm{ M}}{[\mathrm{Cd^{2+}}](6.25\times10^{-4}\textrm{ M})} = (0.37)(2.9\times10^{16})\]. The best way to appreciate the theoretical and practical details discussed in this section is to carefully examine a typical complexation titrimetric method. 0000001814 00000 n Now that we know something about EDTAs chemical properties, we are ready to evaluate its usefulness as a titrant. Next, we solve for the concentration of Cd2+ in equilibrium with CdY2. Protocol B: Determination of Aluminum Content Alone Pipet a 10.00 ml aliquot of the antacid sample solution into a 125 ml. Contrast this with Y4-, which depends on pH. The first four values are for the carboxylic acid protons and the last two values are for the ammonium protons. (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. For a titration using EDTA, the stoichiometry is always 1:1. \[\alpha_{\textrm Y^{4-}} \dfrac{[\textrm Y^{4-}]}{C_\textrm{EDTA}}\tag{9.11}\]. (Show main steps in your calculation). To indicate the equivalence points volume, we draw a vertical line corresponding to 25.0 mL of EDTA. %PDF-1.4 % In addition to its properties as a ligand, EDTA is also a weak acid. 0000002034 00000 n Beginning with the conditional formation constant, \[K_\textrm f'=\dfrac{[\mathrm{CdY^{2-}}]}{[\mathrm{Cd^{2+}}]C_\textrm{EDTA}}=\alpha_\mathrm{Y^{4-}} \times K_\textrm f = (0.37)(2.9\times10^{16})=1.1\times10^{16}\], we take the log of each side and rearrange, arriving at, \[\log K_\textrm f'=-\log[\mathrm{Cd^{2+}}]+\log\dfrac{[\mathrm{CdY^{2-}}]}{C_\textrm{EDTA}}\], \[\textrm{pCd}=\log K_\textrm f'+\log\dfrac{C_\textrm{EDTA}}{[\mathrm{CdY^{2-}}]}\]. Report the purity of the sample as %w/w NaCN. a metal ions in italic font have poor end points. The concentration of Ca2+ ions is usually expressed as ppm CaCO 3 in the water sample. Figure 9.28 Titration curve for the titration of 50.0 mL of 5.00103 M Cd2+ with 0.0100 M EDTA at a pH of 10 and in the presence of 0.0100 M NH3. Finally, a third 50.00-mL aliquot was treated with 50.00 mL of 0.05831 M EDTA, and back titrated to the murexide end point with 6.21 mL of 0.06316 M Cu2+. We also will learn how to quickly sketch a good approximation of any complexation titration curve using a limited number of simple calculations. h`. of which 1.524103 mol are used to titrate Ni. A complexometric titration method is proposed to determine magnesium oxide in flyash blended cement. EDTA forms a chelation compound with magnesium at alkaline pH. Lets use the titration of 50.0 mL of 5.00103 M Cd2+ with 0.0100 M EDTA in the presence of 0.0100 M NH3 to illustrate our approach. The point in a titration when the titrant and analyte are present in stoichiometric amounts is called the equivalence point. First, however, we discuss the selection and standardization of complexation titrants. Complexometric titration is used for the estimation of the amount of total hardness in water. The free magnesium reacts with calmagite at a pH of 10 to give a red-violet complex. For example, we can identify the end point for a titration of Cu2+ with EDTA, in the presence of NH3 by monitoring the titrands absorbance at a wavelength of 745 nm, where the Cu(NH3)42+ complex absorbs strongly. A second 50.00-mL aliquot was treated with hexamethylenetetramine to mask the Cr. 0000038759 00000 n Calcium. varied from 0 to 41ppm. 0000008376 00000 n Titration is one of the common method used in laboratories which determines the unknown concentration of an analyte that has been identified. Calmagite is used as an indicator. Of the cations contributing to hardness, Mg2+ forms the weakest complex with EDTA and is the last cation to be titrated. Add 2 mL of a buffer solution of pH 10. B = mg CaCO3 equivalent to 1 ml EDTA Titrant. Adjust the samples pH by adding 12 mL of a pH 10 buffer containing a small amount of Mg2+EDTA. Dilute 20ml of the sample in Erlenmeyer flask to 40ml by adding 20ml of distilled water. Solution for Calculate the % Copper in the alloy using the average titration vallue. Having determined the moles of Ni, Fe, and Cr in a 50.00-mL portion of the dissolved alloy, we can calculate the %w/w of each analyte in the alloy. Although most divalent and trivalent metal ions contribute to hardness, the most important are Ca2+ and Mg2+. 0000023545 00000 n 0000001334 00000 n You will work in partners as determined by which unknown was chosen. to give a conditional formation constant, Kf, that accounts for both pH and the auxiliary complexing agents concentration. We will use this approach when learning how to sketch a complexometric titration curve. Pipette 10 mL of the sample solution into a conical flask. This reaction can be used to determine the amount of these minerals in a sample by a complexometric titration. \[\begin{align} The titration is done with 0.1 mol/l AgNO3 solution to an equivalence point. Why is the sample buffered to a pH of 10? Figure 9.29c shows the third step in our sketch. If we adjust the pH to 3 we can titrate Ni2+ with EDTA without titrating Ca2+ (Figure 9.34b). [\mathrm{CdY^{2-}}]&=\dfrac{\textrm{initial moles Cd}^{2+}}{\textrm{total volume}}=\dfrac{M_\textrm{Cd}V_\textrm{Cd}}{V_\textrm{Cd}+V_\textrm{EDTA}}\\ Click Use button. 0000021941 00000 n 2. There are 3 steps to determining the concentration of calcium and magnesium ions in hard water using the complexometric titration method with EDTA: Make a standard solution of EDTA. 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, \[K_\textrm f''=K_\textrm f\times\alpha_\mathrm{Y^{4-}}\times\alpha_\mathrm{Cd^{2+}}=\dfrac{[\mathrm{CdY^{2-}}]}{C_\textrm{Cd}C_\textrm{EDTA}}\tag{9.14}\]. In this section we will learn how to calculate a titration curve using the equilibrium calculations from Chapter 6. T! Calculation. 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. The experimental approach is essentially identical to that described earlier for an acidbase titration, to which you may refer. CJ OJ QJ ^J aJ h`. In this study The EDTA was standardized by the titration method as well. Other common spectrophotometric titration curves are shown in Figures 9.31b-f. 0000002997 00000 n An analysis done on a series of samples with known concentrations is utilized to build a calibration curve. 3. Click here to review your answer to this exercise. Standardize against pure zinc (Bunker Hill 99.9985%) if high purity magnesium is not available. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Hardness of water is a measure of its capacity to precipitate soap, and is caused by the presence of divalent cations of mainly Calcium and Magnesium. 1 mol EDTA. In addition, EDTA must compete with NH3 for the Cd2+. 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. Report the molar concentration of EDTA in the titrant. (Note that in this example, the analyte is the titrant. h`. Most metallochromic indicators also are weak acids. h, CJ H*OJ QJ ^J aJ mHsH(h Download determination of magnesium reaction file, open it with the free trial version of the stoichiometry calculator. State the value to 5 places after the decimal point. 0000001481 00000 n All Answers (10) 1) Be sure the pH is less than 10, preferably about 9.5-9.7. ! The reason we can use pH to provide selectivity is shown in Figure 9.34a. Magnesium can be easily determined by EDTA titration in the pH10 against Eriochrome BlackT. If the solution initially contains also different metal ions, they should be removed or masked, as EDTA react easily with most cations (with the exception of alkali metals). Add 4 drops of Eriochrome Black T to the solution. 2. last modified on October 27 2022, 21:28:28. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright . 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. 0000023793 00000 n Figure 9.30 (a) Predominance diagram for the metallochromic indicator calmagite showing the most important form and color of calmagite as a function of pH and pMg, where H2In, HIn2, and In3 are uncomplexed forms of calmagite, and MgIn is its complex with Mg2+. Each ml of 0.1M sodium thiosulphate is equivalent to 0.02703 g of FeCI3,6H2O. The fully protonated form of EDTA, H6Y2+, is a hexaprotic weak acid with successive pKa values of. 0 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. Step 1: Calculate the conditional formation constant for the metalEDTA complex. (i) Calculation method For this method, concentration of cations should be known and then all concentrations are expressed in terms of CaCO 3 using Eq. Elution of the compounds of interest is then done using a weekly acidic solution. 0000002315 00000 n U! 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. %%EOF The titration is performed by adding a standard solution of EDTA to the sample containing the Ca. Some!students! Repeat the titration twice. 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. the reason for adding Mg-EDTA complex as part of the NH 4 Cl - NH 4 OH system explained in terms of requirement of sufficient inactive Mg2+ ions to provide a sharp colour change at the endpoint. The scale of operations, accuracy, precision, sensitivity, time, and cost of a complexation titration are similar to those described earlier for acidbase titrations. Estimation of magnesium ions in the given sample: 20 mL of the given sample of solution containing magnesium ions is pipetted into a 250 Erlenmeyer flask, the solution is diluted to 100 mL, warmed to 40 degrees C, 2 mL of a buffer solution of pH 10 is added followed by 4 drops of Eriochrome black T solution. Calculate titration curves for the titration of 50.0 mL of 5.00103 M Cd2+ with 0.0100 M EDTA (a) at a pH of 10 and (b) at a pH of 7. EDTA Titration You would like to perform a titration of 50.00 mL of a 1.00 x 10-4 M Zn2+ solution with a 1.00 x 10-4 M EDTA solution. 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). Add 12 drops of indicator and titrate with a standard solution of EDTA until the red-to-blue end point is reached (Figure 9.32). The burettte is filled with an EDTA solution of known concentration. Take a sample volume of 20ml (V ml). EDTA solution. The determination of Ca2+ is complicated by the presence of Mg2+, which also reacts with EDTA. Thus, when the titration reaches 110% of the equivalence point volume, pCd is logKf 1. Truman State University CHEM 222 Lab Manual Revised 01/04/08 REAGENTS AND APPARATUS 0000001920 00000 n The other three methods consisted of direct titrations (d) of mangesium with EDTA to the EBT endpoint after calcium had been removed. The hardness of a water source has important economic and environmental implications. Select a volume of sample requiring less than 15 mL of titrant to keep the analysis time under 5 minutes and, if necessary, dilute the sample to 50 mL with distilled water. 3. 2. The amount of calcium present in the given sample can be calculated by using the equation. Why is a small amount of the Mg2+EDTA complex added to the buffer? The actual number of coordination sites depends on the size of the metal ion, however, all metalEDTA complexes have a 1:1 stoichiometry. Titrating with 0.05831 M EDTA required 35.43 mL to reach the murexide end point. This can be analysed by complexometric titration. 0000009473 00000 n Figure 9.31 Examples of spectrophotometric titration curves: (a) only the titrand absorbs; (b) only the titrant absorbs; (c) only the product of the titration reaction absorbs; (d) both the titrand and the titrant absorb; (e) both the titration reactions product and the titrant absorb; (f) only the indicator absorbs. The pH affects a complexometric EDTA titration in several ways and must be carefully controlled. It can be determined using complexometric titration with the complexing agent EDTA. a mineral analysis is performed, hardness by calculation can be reported. 0000000832 00000 n +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 For the purposes of this lab an isocratic gradient is used. The reaction of Mg2+ with EDTA may be expressed as: Mg2+ + H2Y2- = MgY-2 + 2H+ The structure of EDTA and the magnesium-EDTA complex (without the hydrogen atoms) is shown below: The endpoint of the titration is determined by the . The titrations end point is signaled by the indicator calmagite. To prevent an interference the pH is adjusted to 1213, precipitating Mg2+ as Mg(OH)2. Prepare a standard solution of magnesium sulfate and titrate it against the given EDTA solution using Eriochrome Black T as the indicator. Because EDTA forms a stronger complex with Cd2+ it will displace NH3, but the stability of the Cd2+EDTA complex decreases. Hardness EDTA as mg/L CaCO3 = (A*B*1000)/ (ml of Sample) Where: A = ml EDTA Solution Used. At a pH of 3, however, the conditional formation constant of 1.23 is so small that very little Ca2+ reacts with the EDTA. Step 4: Calculate pM at the equivalence point using the conditional formation constant. Solutions of Ag+ and Hg2+ are prepared using AgNO3 and Hg(NO3)2, both of which are secondary standards. The reaction that takes place is the following: (1) C a 2 + + Y 4 C a Y 2 Before the equivalence point, the Ca 2+ concentration is nearly equal to the amount of unchelated (unreacted) calcium since the dissociation of the chelate is slight. A time limitation suggests that there is a kinetically controlled interference, possibly arising from a competing chemical reaction. The next task in calculating the titration curve is to determine the volume of EDTA needed to reach the equivalence point. Because the pH is 10, some of the EDTA is present in forms other than Y4. The calcium and magnesium ions (represented as M2+ in Eq. In an EDTA titration of natural water samples, the two metals are determined together. The end point is the color change from red to blue. This means that the same concentration of eluent is always pumped through the column. Detection is done using a conductivity detector. This can be done by raising the pH to 12, which precipitates the magnesium as its hydroxide: Mg2+ + 2OH- Mg(OH) 2 hs 5>*CJ OJ QJ ^J aJ mHsH 1h It is sometimes termed as volumetric analysis as measurements of volume play a vital role. |" " " " " " " # # # # # >$ {l{]K=/=h0Z CJ OJ QJ ^J aJ h)v CJ OJ QJ ^J aJ #hk hk 5CJ OJ QJ ^J aJ h 5CJ OJ QJ ^J aJ h)v 5CJ OJ QJ ^J aJ hL 5CJ OJ QJ ^J aJ hk CJ OJ QJ ^J aJ hH CJ OJ QJ ^J aJ hlx% CJ OJ QJ ^J aJ hlx% hlx% CJ OJ QJ ^J aJ hlx% hH CJ OJ QJ ^J aJ (h- hH CJ OJ QJ ^J aJ mHsH (hk hk CJ OJ QJ ^J aJ mHsH>$ ?$ % % P OQ fQ mQ nQ R yS zS T T T U U U U U U U U U U !U 8U 9U :U ;U =U ?U @U xj j h7 UmH nH u h? Calcium and Magnesium ion concentration determination with EDTA titration 56,512 views Dec 12, 2016 451 Dislike Share Save Missy G. 150 subscribers CHEM 249 Extra credit by Heydi Dutan and. The quantitative relationship between the titrand and the titrant is determined by the stoichiometry of the titration reaction. For example, after adding 30.0 mL of EDTA, \[\begin{align} This shows that the mineral water sample had a relatively high. Figure 9.34 Titration curves illustrating how we can use the titrands pH to control EDTAs selectivity. A new spectrophotometric complexometric titration method coupled with chemometrics for the determination of mixtures of metal ions has been developed. and pCd is 9.77 at the equivalence point. We will also need indicator - either in the form of solution, or ground with NaCl - 100mg of indicator plus 20g of analytical grade NaCl. Solving gives [Cd2+] = 4.71016 M and a pCd of 15.33. trailer Step 2: Calculate the volume of EDTA needed to reach the equivalence point. 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. After the equilibrium point we know the equilibrium concentrations of CdY2- and EDTA. If desired, calcium could then be estimated by subtracting the magnesium titration (d) from the titration for calcium plus magnesium (a). The formation constant for CdY2 in equation 9.10 assumes that EDTA is present as Y4. 268 0 obj <>stream Reactions taking place How do you calculate EDTA titration? 4 23. 0000002921 00000 n At any pH a mass balance on EDTA requires that its total concentration equal the combined concentrations of each of its forms. Figure 9.26 Structures of (a) EDTA, in its fully deprotonated form, and (b) in a six-coordinate metalEDTA complex with a divalent metal ion. Show your calculations for any one set of reading. Submit for analysis. EDTA. Volume required to neutralise EDTA. Calculations. The titration uses, \[\mathrm{\dfrac{0.05831\;mol\;EDTA}{L}\times 0.02614\;L\;EDTA=1.524\times10^{-3}\;mol\;EDTA}\]. End point of magnesium titration is easily detected with Eriochrome BlackT. To perform titration we will need titrant - 0.01M EDTA solution and ammonia pH10.0 buffer. The solid lines are equivalent to a step on a conventional ladder diagram, indicating conditions where two (or three) species are equal in concentration. The resulting spectrophotometric titration curve is shown in Figure 9.31a. To maintain a constant pH during a complexation titration we usually add a buffering agent. In 1945, Schwarzenbach introduced aminocarboxylic acids as multidentate ligands. Table 9.10 provides values of Y4 for selected pH levels. Add a pinch of Eriochrome BlackT ground with sodium chloride (100mg of indicator plus 20g of analytical grade NaCl). This point coincides closely to the endpoint of the titration, which can be identified using an . Preparation of 0.025M MgSO4.7H2O: Dissolve 0.616 grams of analytic grade magnesium sulfate into a 100 mL volumetric flask. Water hardness is determined by the total concentration of magnesium and calcium. Report the concentration of Cl, in mg/L, in the aquifer. Titration is a method to determine the unknown concentration of a specific substance (analyte) dissolved in a sample of known concentration. In the method described here, the titrant is a mixture of EDTA and two indicators. 0000002393 00000 n endstream endobj 267 0 obj <>/Filter/FlateDecode/Index[82 161]/Length 27/Size 243/Type/XRef/W[1 1 1]>>stream The obtained average molarity of EDTA (0.010070.00010 M) is used in Table 2 to determine the hardness of water. It is used to analyse urine samples. Neither titration includes an auxiliary complexing agent. Add 1 mL of ammonia buffer to bring the pH to 100.1. Table 9.14 provides examples of metallochromic indicators and the metal ions and pH conditions for which they are useful. An important limitation when using an indicator is that we must be able to see the indicators change in color at the end point. leaving 4.58104 mol of EDTA to react with Cr. given: Devarda alloy= 0.518g [EDTA] = 0.02 moldm^3 average titration