(a) Write down the structure of EDTA molecule and show the complex structure with Pb2+ . (b) When do you need to perform back titration? (c) Ni2+ can be analyzed by a back titration using standard Zn2+ at pH 5.5 with xylenol orange indicator. A solution containing 25.00 mL of Ni2+ in dilute HCl is treated with 25.00 mL of 0.05283 M Na2EDTA. The solution is neutralized with NaOH, and the pH is adjusted to 5.5 with acetate buffer. The solution turns yellow when a few drops of indicator are added. Titration with 0.02299 M Zn2+ requires 17.61 mL to reach the red end point. What is the molarity of Ni2+ in the unknown?

(a) Write down the structure of EDTA molecule and show the complex structure with Pb2+ . (b) When do you need to perform back titration? (c) Ni2+ can be analyzed by a back titration using standard Zn2+ at pH 5.5 with xylenol orange indicator. A solution containing 25.00 mL of Ni2+ in dilute HCl is treated with 25.00 mL of 0.05283 M Na2EDTA. The solution is neutralized with NaOH, and the pH is adjusted to 5.5 with acetate buffer. The solution turns yellow when a few drops of indicator are added. Titration with 0.02299 M Zn2+ requires 17.61 mL to reach the red end point. What is the molarity of Ni2+ in the unknown?

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter17: Complexation And Precipitation Reactions And Titrations

Section: Chapter Questions

Problem 17.33QAP

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(ii) Consider the titration of 25.00 mL of 0.02000 M CaSO4 with 0.01000 M EDTA at pH 10.00. Write the chemical equation for this titration and calculate the conditional formation constant for this reaction. (iii) From (ii) calculate the concentration of Ca2+ and pCa2+ at the volume of 20.0 mL of EDTA added.
Chromel is an alloy composed of nickel, iron and chromium. A 0.6553-g sample was dissolved and diluted to 250.0 mL. When a 50.00-mL aliquot of 0.05173 M EDTA was mixed with an equal volume of the diluted sample, all three ions were chelated, and a 5.34-mL back titration with 0.06139 M copper (II) was required.The chromium in a second 50.0-mL aliquot was masked through the addition of hexamethylenetetramine; titration of the Fe and Ni required 36.98 mL of 0.05173M EDTA. Iron and chromium were masked with pyrophosphate in a third 50.00-mL aliquot, and the nickel was titrated with 24.53 mL of the EDTA solution. Calculate the percentage of Cr in the alloy. Express your answer in 2 decimal places.
Chromel is an alloy composed of nickel, iron, and chromium. A 0.6418-g sample was dissolved and diluted to 250.0 mL. When a 50.00-mL aliquot of 0.05173 M EDTA was mixed with an equal volume of the diluted sample, all three ions were chelated, and a 5.27-mL back-titration with 0.06139 M copper(II) was required. The chromium in a second 50.0-mL aliquot was masked through the addition of hexamethylenetetramine; titration of the Fe and Ni required 35.81 mL of 0.05173 M EDTA. Iron and chromium were masked with pyrophosphate in a third 50.0-mL aliquot, and the nickel was titrated with 25.77 mL of the EDTA solution. Calculate the percentages of nickel, chromium, and iron in the alloy. Percentage of nickel = % Percentage of iron = Percentage of chromium = % %
Iron(III) is best determined by addition of excess EDTA, followed by back-titration with a metal ion that reacts rapidly with EDTA. A 700.0-mg sample is dissolved, 20.00 mL of 0.0500M EDTA is added, and the excess EDTA is titrated with 5.08 mL of 0.0420M copper(lI). Calculate the percentage of Fe,O, in the sample.
For complexometric titration of Ca (II) ions in the shell of an egg sample weighing 59,427 g, the necessary processes were applied to the egg shells and a sample of 100 mL was prepared. From the prepared sample, 1 mL was taken and diluted to 100 mL, the pH was adjusted, and two drops of EBT indicator were dripped on it. The prepared solution was titrated with 27.4 mL of EDTA solution set at 0.0097 M. Calculate the amount of calcium in the sample in CaCO3%. (Ca = 40g / mol, CaCO3= 100g / mol)
A 25.00 ml of Ni2+ solution was diluted in HCl and treated with 25.00 ml of 0.05283 MNa2EDTA. The solution was neutralized with NaOH followed by addition of acetate buffer untilthe pH 5.5. The solution turns yellow after addition of few drops of xylenol orange indicator.Back titration using standard 0.022 MZn2+ at pH 5.5 requires 17.61 ml until end point, onwhich the solution will turn red. Calculate for the molarity of the unknown.
Chromel is an alloy composed of nickel, iron and chromium.A 0.6472 g sample was dissolved and diluted to 250 mL. When a50 mL aliquot of 0.05182 M EDTA was mixed with an equal volumeof the diluted sample and all the three ions were chelated, a 5.11 mLback titration with 0.06241 M copper (II) was required.The chromium in a second 50 mL aliquot was masked through theaddition of hexamethylenetetramine, titration of the Fe and Nirequired 36.28 mL of 0.05182 M EDTA.Iron and chromium were masked with pyrophosphate in a third50 mL aliquot and the nickel was titrated with 25.91 mL of theEDTA solution.Calculate the percentage of nickel, chromium and iron in thealloy.
A1.3174-g sample containing the chloride salts of magnesium, mercury(II), and zinc was dissolved in 250.0 ml of solution. A 50.00-mL aliquot was treated with 1o ml of an NH,/NH,CI buffer at pH 10 followed by 25.00 ml of o.o5331 M EDTA. After a few minutes of mixing, the excess EDTA was back titrated with 11.43 mL of o.o1816 M MagCl.. A second 50.00-mL aliquot was made basic and treated with excess NaCN, complexing both the mercury and zinc. The magnesium in this sample required 16.83 mL of o.005583 M EDTA for titration. The solution remaining at the end point of this titration was treated with excess formaldehyde, which reacts with the free CN and Zn(CN),: OH CN + HCHO + H.O H.C + OH CN The liberated Zn" required 28.47 mL of the EDTA for titration. Calculate the percentage of each metal in the sample. Answer: 0.8669 % Mg: 3.94 % Zn; 19.4 % Hg
What is the equivalence volume when 0.0500 M EDTA is titrated with 100.0 mL of 0.0500 M Mn+ buffered to a pH of 9.00?
2. Titration of Ca²+ and Mg²+ in a 50mL sample of hard water required 23.65mL of 0.01205M EDTA. A second 50mL aliquot was made strongly basic with NaOH to precipitate Mg2+ as Mg(OH)2. The supernatant liquid was titrated with 14.53mL of the EDTA solution. Calculate a. concentration in ppm of CaCO3 in the sample. b. concentration in ppm of MgCO3 in the sample.
A 25.00 mL aliquot of sample containing Hg in dilute nitric acid was treated with 10.00 mL of 0.04882 M EDTA and the pH was adjusted to 10. The excess EDTA was titrated with 24.66 mL of 0.01137 M Mg. What is the molarity of Hg in the original solution?
EXAMPLE: Chromium(III) is slow to react with EDTA (H4Y) and is therefore determined by back-titration. A pharmaceutical preparation containing chromium(III) is analyzed by treating a 2.63g sample with 5mL of (0.0103M) EDTA. Following reaction, the unreacted EDTA is back-titrated with 1.32mL of (0.0112M) zinc solution. What is the percent chromium chloride in the pharmaceutical preparation?