An analysis for borohydride ion is based on its reaction with Ag+: BH4- + 8Ag+ + 8OH--> H2BO3- + 8Ag(s) + 5H2O The purity of a quantity of KBH4 to be used was established by diluting 3.213 g of the material to exactly 500.0 mL, treating a 100.0-mL aliquot with 50.00 mL of 0.2221 M AgNO3, and titrating the excess silver ion with 3.36 mL of 0.0397 M KSCN. Calculate the percent purity of the KBH4 (53.941 g/mol).

An analysis for borohydride ion is based on its reaction with Ag+: BH4- + 8Ag+ + 8OH--> H2BO3- + 8Ag(s) + 5H2O The purity of a quantity of KBH4 to be used was established by diluting 3.213 g of the material to exactly 500.0 mL, treating a 100.0-mL aliquot with 50.00 mL of 0.2221 M AgNO3, and titrating the excess silver ion with 3.36 mL of 0.0397 M KSCN. Calculate the percent purity of the KBH4 (53.941 g/mol).

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter11: Solutions

Section: Chapter Questions

Problem 70AP

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2. An analysis for borohydride ion is based on its reaction with Ag+: BH4 - + 8Ag+ + 8OH- -> H2BO3 - + 8Ag(s) + 5H2O The purity of a quantity of KBH4 to be used was established by diluting 3.213 g of the material to exactly 500.0 mL, treating a 100.0-mL aliquot with 50.00 mL of 0.2221 M AgNO3, and titrating the excess silver ion with 3.36 mL of 0.0397 M KSCN. Calculate the percent purity of the KBH4 (53.941 g/mol).
The formaldehyde content of a pesticide was determined by weighing 0.9327 g of the liquid sample into a flask containing 50.0 mL of 0.08624 M NaOH and 50 mL of 3% H2O2. It was heated then cooled. After cooling, the excess base was titrated with 27.8 mL of 0.06325 M H2SO4. Calculate the percentage of HCHO in the sample.
A stock solution containing Mn2+ ions was prepaned by dissolving 1.584 g pure manganese metal in nitric acid and diluting to a final volume of 1.000 L. The following solutions were then prepared by dilution: For solution A, 50.00 mL of stock solution was diluted to 1000.0 mL. For solution B, 10.00 mL of solution A was diluted to 250.0 mL. For solution C, I 0.00 mL of solution Bwas diluted to 500.0 mL. Calculate the concentrations of the stock solution and solutions A,B, and C.
A sample of CaCO3 (molar mass=100.1) weighing 0.4856 g is dissolved in HCl and the solution diluted to 500.0 mL in a volumetric flask. A 25.00-mL aliquot requires 21.37 mL of an EDTA solution for titration. How many grams of Na2H2Y.2H2O (molar mass=372.2) are required to prepare 500.0 mL of this solution.
A 1.219-g containing (NH4)2SO4, NH4NO3, and nonreactive substances was diluted to 200 mL in a volumetric flask. A 50.00-mL aliquot was made basic with strong alkali, and the liberated NH3 was distilled into 30.00-mL of 0.08421 M HCl. The excess HCl required 10.17 mL of 0.08802 M NaOH. A 25-mL aliquot of the sample was made alkaline after the addition of Devarda’s alloy, and the NO3- was reduced to NH3. The NH3 from both the NH4+ and NO3- was then distilled into 30.00 mL of the standard acid and back titrated with 14.16 mL of base. Calculate the percentage of (NH4)2SO4 and NH4NO3 in the sample.
The amount of protein in a sample of cheese is determined by a Kjeldahl analysis for nitrogen. After digesting a 0.9814-g sample of cheese, the nitrogen is oxidized to NH4+, converted to NH3 with NaOH, and distilled into a collection flask containing 50.00 mL of 0.1047 M HCl. The excess HCl is then back titrated with 0.1183 M NaOH, requiring 22.84 mL to reach the bromothymol blue end point. Report the %w/w protein in the cheese given that there is 6.38 g of protein for every gram of nitrogen in most dairy products.
A 0.5 g sample of an alloy containing 30% (m/m) iron (MM 55.84 g/mol) is dissolved in acid and diluted to 1 L with deionized water. A 10 mL aliquot was taken for analysis, conveniently diluted and included with an excess of ammonium hydroxide, which led to the formation of a reddish solid. After filtration and washing, the solid was calcined to Fe2O3 (MM 159.69 g/mol). Calculate the mass of this final product.
29. How much 0.600 N base must be added to 750 mL of a 0.200 N base in order for the solution to be 0.300 N? 30. Calculate the molarity of KMnO4 (158m04 g/mol) sok standardized against 1.356 grams Na2C2O4 (134 g/mol) requiring 25 mL of the solution in acidic medium?
A 0.6883 gram sample of impure potassium chlorate was treated with 45.00 mL of 0.1020 M Fe(NH4)2(SO4)2. The reaction is: ClO3-+6Fe2++6H+->Cl-+6Fe3++3H2O When the reaction was complete, the excess Fe(II) was back-titrated with 9.004 mL of 0.01734 M K2Cr2O7. Cr2O7-+6Fe2++14H+->2Cr3++6Fe3++7H2O Calculate the percent KClO3 (FW = 122.55) in the sample.
Use the following atomic masses (in g/mol): Mg = 24.31; H = 1; S = 32.06; O = 16; Na = 23; Cl = 35. 45; Ca = 40.08; C = 12.01; N = 14.01; Mg = 24.31 5.A sample of Chlorpheniramine Maleate (99.82%) weighing 0.502g was assayed by non-aqueous titrimetry and was found to be equivalent to 22.2mL of perchloric acid. Calculate for the normality of perchloric acid. Each mL of 0.1N perchloric acid is equivalent to 19.54mg of Chlorpheniramine Maleate.
An unknown sample weighing 1.5098 g was acidified with 3.0 M H2SO4 to dissolve the copper compounds and diluted with 30 mL distilled water. This was followed by the addition of excess KI producing I2 and CuI precipitate from Cu2+ (Reaction 1). Then, the liberated I2 reacted with the excess KI forming triiodide anion (Reaction 2), which was then titrated with Na2S2O3 titrant (Reaction 3). This entire solution required 17.60 mL of the titrant to reach the starch end point. What are the balanced chemical equations for reactions 1-3? What is the mole ration between Cu2+ and S2O32-?
The tetraethyl lead Pb(C2H5)4 in a 25.00 mL sample of aviation gasoline was shaken with 15.00 mL of 0.02179 M I2. (Hint: one mole of I2 reacts with one mole of the tetraethyl lead). After the reaction was complete, the unused I2 was titrated with 7.37 mL of 0.02959 M thiosulfate solution. Calculate the weight of Pb(C2H5)4 (MW = 323.4 g/mol) in each liter of gasoline.