2. To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co2+] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. Absorbance 0.90- 0.80- 0.70- 0.60- 0.50 0.40- 0.30- 0.20- 0.10- 0.00++ 0 0.005 0.0103 0.015 Concentration (M) .04. A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq). (a) What is the [Co2+] in the solution if the absorbance of a sample of the solution is 0.74 ? (b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution. (c) Calculate the mass percent of Co in the 0.630 g sample of the ore.

2. To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co2+] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. Absorbance 0.90- 0.80- 0.70- 0.60- 0.50 0.40- 0.30- 0.20- 0.10- 0.00++ 0 0.005 0.0103 0.015 Concentration (M) .04. A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq). (a) What is the [Co2+] in the solution if the absorbance of a sample of the solution is 0.74 ? (b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution. (c) Calculate the mass percent of Co in the 0.630 g sample of the ore.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter10: Atomic Emission Spectrometry

Section: Chapter Questions

Problem 10.11QAP

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Absorbance Beer-Lambert's Law (Spectrophotometry) #2 To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co"] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. 0.80 0.70- 8 0.60- 0.50- 0.40- 0.30 0.20- 0.10- ++- 0.015 Concentration (M) A 0.6 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with 2+ water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co'(aq). a. What is the (Co] in the solution if the absorbance of a sample of the solution is 0.74? b. Calculate the number of moles of CoT(ag) in the 50.00 mL solution. 2+ C. Calculate the mass percent of Co in the 0.630 g sample of the ore.
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