he sulfur content of insoluble sulfides that do not readilydissolve in acid can be measured by oxidation with Br2to SO42.25Metal ions are then replaced with Hby an ion-exchange column,and sulfate is precipitated as BaSO4with a known excess ofBaCl2. The excess Ba2is then titrated with EDTA to determinehow much was present. (To make the indicator end point clearer,a small, known quantity of Zn2also is added. The EDTA titratesboth the Ba2and the Zn2.) Knowing the excess Ba2, we cancalculate how much sulfur was in the original material. To analyzethe mineral sphalerite (ZnS, FM 97.46), 5.89 mg of powderedsolid were suspended in a mixture of CCl4and H2O containing1.5 mmol Br2. After 1 h at 20 C and 2 h at 50 C, the powder dis-solved and the solvent and excess Br2were removed by heating.The residue was dissolved in 3 mL of water and passed throughan ion-exchange column to replace Zn2with H. Then 5.000 mLof 0.014 63 M BaCl2were added to precipitate all sulfate as BaSO4.After the addition of 1.000 mL of 0.010 00 M ZnCl2and 3 mL of ammonia buffer, pH 10, the excess Ba2and Zn2required 2.39 mLof 0.009 63 M EDTA to reach the Calmagite end point. Find theweight percent of sulfur in the sphalerite. What is the theoretical value?
he sulfur content of insoluble sulfides that do not readilydissolve in acid can be measured by oxidation with Br2to SO42.25Metal ions are then replaced with Hby an ion-exchange column,and sulfate is precipitated as BaSO4with a known excess ofBaCl2. The excess Ba2is then titrated with EDTA to determinehow much was present. (To make the indicator end point clearer,a small, known quantity of Zn2also is added. The EDTA titratesboth the Ba2and the Zn2.) Knowing the excess Ba2, we cancalculate how much sulfur was in the original material. To analyzethe mineral sphalerite (ZnS, FM 97.46), 5.89 mg of powderedsolid were suspended in a mixture of CCl4and H2O containing1.5 mmol Br2. After 1 h at 20 C and 2 h at 50 C, the powder dis-solved and the solvent and excess Br2were removed by heating.The residue was dissolved in 3 mL of water and passed throughan ion-exchange column to replace Zn2with H. Then 5.000 mLof 0.014 63 M BaCl2were added to precipitate all sulfate as BaSO4.After the addition of 1.000 mL of 0.010 00 M ZnCl2and 3 mL of ammonia buffer, pH 10, the excess Ba2and Zn2required 2.39 mLof 0.009 63 M EDTA to reach the Calmagite end point. Find theweight percent of sulfur in the sphalerite. What is the theoretical value?
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ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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The sulfur content of insoluble sulfides that do not readilydissolve in acid can be measured by oxidation with Br2to SO42.25Metal ions are then replaced with Hby an ion-exchange column,and sulfate is precipitated as BaSO4with a known excess ofBaCl2. The excess Ba2is then titrated with EDTA to determinehow much was present. (To make the indicator end point clearer,a small, known quantity of Zn2also is added. The EDTA titratesboth the Ba2and the Zn2.) Knowing the excess Ba2, we cancalculate how much sulfur was in the original material. To analyzethe mineral sphalerite (ZnS, FM 97.46), 5.89 mg of powderedsolid were suspended in a mixture of CCl4and H2O containing1.5 mmol Br2. After 1 h at 20 C and 2 h at 50 C, the powder dis-solved and the solvent and excess Br2were removed by heating.The residue was dissolved in 3 mL of water and passed throughan ion-exchange column to replace Zn2with H. Then 5.000 mLof 0.014 63 M BaCl2were added to precipitate all sulfate as BaSO4.After the addition of 1.000 mL of 0.010 00 M ZnCl2and 3 mL of ammonia buffer, pH 10, the excess Ba2and Zn2required 2.39 mLof 0.009 63 M EDTA to reach the Calmagite end point. Find theweight percent of sulfur in the sphalerite. What is the theoretical value?
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