Question

Ligand X forms a complex with both cobalt and copper, each of which has a maximum absorbance at 510 nm and 645 nm, respectively. A 0.241 g sample containing cobalt and copper was dissolved and diluted to a volume of 100.0 mL. A solution containing ligand X was added to a 50.0 mL aliquot of the sample solution and diluted to a final volume of 100.0 mL. The measured absorbance of the unknown solution was 0.447 at 510 nm and 0.327 at 645 nm, when measured with a 1.00 cm cell. The molar absorptivities of the cobalt and copper complexes at each wavelength are shown in the table. Wavelength Molar Absorptivity (€, M-?cm-?) Co Cu 2, nm 510 5696 37561 1.280 x 103 645 18060 What is the concentration of cobalt and copper in the final diluted solution? [Co2+] = 0 Cu2+1 = What is the weight percent of cobalt (FM = 58.933 g/mol) and copper (FM = 63.546 g/mol) in the 0.241 g sample? wt% Co2+ = wt% Cu2+ =

Answer 1

solution t, nm Co cu 510 37561 5696 1280 | 18060 645 Ccu = 0.447 - 3756 ICCO I co 5696 eq 1280ccot 18060 x 0.447-37561cco = 0.327 5696 1280cco + 3.17 x(0.447-37561660).0.327 1280cc0 + (1.41699 - 119068Cc.) - 0.327 1.41699 -0.327 = 119068 - 1280cco CO 1.089 = 117788 CCO diluted = cco = 9.245x156] substitute cco value in eq ④ con = 0.447 - 37561 (9.245X100) 5696 0.092 -0.) Cu och 5696 [ccu = 1,75x10m

50mL diluted to 100mL or a times. stock concentration=scut1= 2x1.75X 10 M Jeu?t= 3.5x105 m 9, 24X10 stock concentration co 2 cost = 1.848x10ml 2 + S co moles of cost - (1.848x105x0.14) = 1.848810 Moles moles of uut (3.5x105x0.1L) - 3.5x100 moles is weight of cot: 101.948x10*x 58.933), - @ 108.90 xioºg - 108.9u9 weight of cut. (35X10X 63.546), - 222,4x10°g. 222.4ug 0.2419 = 0.24 241mg wt J co - 108.9 X 10 x 100y = 0.045% 241 mg - 3 out y. mt. 222.4 x 10mg x 100%. = 0.092%. Эч м99