Virtual Lab Question: In an old experiment, students attempted to measure the percentage of cobalt in an unknown. The cobalt ions in three standards were complexed with thiocyanate, forming Co(SCN) 42- ions, and then analyzed
b. Given that the cuvette path length was 1.17 cm, use the slope of this line to calculate the molar absorptivity of the cobalt complex at this wavelength. (Assume Beer’s law is obeyed.)
c. An unknown cobalt sample was treated as follows: 40.8 mg of the unknown was dissolved in solvent to prepare 50.00 mL of solution in a volumetric flask. 4.00 mL of this solution was treated with thiocyanate, and diluted to a final volume of 50.00 mL. A sample of this final solution was placed in the same cuvette as the standards, and showed an absorbance of 0.38 at 625 nm. Determine the percentage of cobalt in the original unknown, given that the
![3.
Virtual Lab Question: In an old experiment, students
attempted to measure the percentage of cobalt
in an unknown. The cobalt ions in three standards
were complexed with thiocyanate, forming
Co(SCN) 42- ions, and then analyzed
spectrophotometrically at 625 nm. The data in the
table shown was obtained by one pair of students.
a. Using quality graph paper, plot absorbance as a function of concentration using this data.
9(D) - 3
[Co(SCN)4]²-/ M
0
0.00015
0.00022
0.00042
Absorbance (625 nm)
0
0.29
0.45
0.90](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F2332e5eb-151a-4a7f-954e-ef2a695430ff%2Faca63c8c-d554-4102-9cf6-cef8677f630d%2Fes4nvte_processed.jpeg&w=3840&q=75)
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