Chapter 37, Problem 3ASA

. An antacid tablet, weighing 1.25 g, was dissolved in a 1.0 L volumetric flask to allow for determination of calcium carbonate and magnesium carbonate contents. After preparing the solution, an aliquot of 10.0 ml was transferred to an Erlenmeyer flask containing a buffer solution with pH = 10. This aliquot was then titrated with EDTA 0.0040 mol/L and the average volume spent was 15.01 mL. To measure calcium after precipitation. After the magnesium was fractionated, a second 10.00 mL aliquot of the stock solution was transferred to an Erlenmeyer flask, and the pH of the present solution was adjusted to a value of approximately 13. In EDTA titration, the volume consumed for observation of the end point was equal to 13.03 mL. Based on this information, a) Outline the two steps involved, representing the related reactions./5 b) Calculate the concentrations of CaCO3 and MgCO3 present in the initial solution./6 c) Calculate the masses of CaCO3 and MgCO3 present in the pellet./6 d) Calculate…

Identify the type of coprecipitation that occurred in the following situation. (a) The precipitation of bulky precipitates (e.g. MgNH4PO4) traps significant amount of the solution in the crystalline precipitate. ____________ (b) The formation of equimolar replacement (Al, Fe) 203 during the precipitation of hydroxides in a solution containing A13+ and Fe3+ _____________ (c) The coprecipitation of soluble ions (e.g. Na+ and CI) in the solution because of the absorption of electrolytes by colloidal precipitates. _____________ (d.) Dust particles may coprecipitate as crystals grow on the surface of the dust particles. ___________ (e.) lons in the solution may be trapped inside the precipitate during the crystal growth process.___________ Fill in the blanks with the following choices: occlusion, mechanical entrapment, surface absorption, mixed crystal formation

Explain why colour of KMnO4 disappears when oxalic acid is added to its solution in acidic medium.

A solution of unknown group I ions gives a white precipitate with HCl.When treated with hot water, it gives a solution to which K2CrO4 is added, and a yellow precipitate forms.The white precipitate that remains after the hot water treatment dissolves completely in NH3. Which ions are present and which are not?

Explain why addition of NH3 or HNO3 to a saturated solution of Cu(OH)2 in contact with solid Cu(OH)2 increases the solubility of the solid.

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.

Calamine, which is used for relief of skin irritations, is a mixture of zinc and iron oxides. A 1.022-g sample of dried calamine was dissolved in acid and diluted to 250.0 mL. A 50.00 mL aliquot was suitably buffered and titrated with 2.40 mL of 0.002727 M ZnY-2 (Zn-EDTA) solution to allow the following reaction: Fe+3 + ZnY-2 → FeY- + Zn+2.  Molecular mass:   Fe2O3  = 165.74 a. The weight of sample in the aliquot portion is _________g ? b. the percentage composition of Fe2O3 in the sample is ______ % ?

Sometimes it is not possible to indicate the end point of a titration.a) How can one proceed then and what is the name of the type of titration that can be performed? Briefly describe. An example in which this method can be used is in the determination of mercury, which forms strong complexes with EDTA, but for which there is no suitable indicator that can indicate the end point. b) You are given the task of determining the Hg2 + concentration in a sample solution? After adding an excess of EDTA, the sample solution is titrated with a magnesium solution. 20.00 ml of a 0.0452 M EDTA solution was added to 30.00 ml of sample solutionThe excess EDTA was determined by adding 0.0500 M Mg 2+ solution, consuming 4.37 ml to the end point.

1. How is complete precipitation assured in the Group III Cations? 2. In the confirmatory test of Magnesium ion, why is it necessary to heat the centrifugate in water bath for 5 minutes? 3. If Magnesium hydroxide is a white gelatinous precipitate, why is the confirmatory result indicated a blue precipitate?