Question

POST LABORATORY QUESTIONS solution appears to be orange, what range of wavelength would you use for analysis of the solution? I. a. Ifa b. How about if the solution was green-blue? 2, a. what absorbance corresponds to a percent transmittance of 59.6 % T? b. What is the percent transmittance for a solution that has an absorbance of 0.49? 3. At a wavelength of 510 nm a 0.12 M solution of CoCla gave a percent transmittance value of28.9 %. The percent transmittance of an "unknown" solution of CoCl2 was found to be 44.2 %. what is the concentration of CoCl2 in the "unknown"? (Assume Beer's law is obeyed)

Answer 1

A = log(I/I_0) A = -log(59.6/100) = --log(596/10000 a = 0.2247 (b) A = -log(I/I_0) = -log(%T) %T = 10^-A = 10^-0.49 %T = 32.365 T tildeequal 32.4% lambda = 510nm C_1(conc of known CoCL_2) = 0.12M = 0.12 mol^-1 = 0.12/1000 mol cm^-3 % T_1 = 28.9% A = -log(T_1) = -log(28.9/100) = -log(0.289) A_1 = 0.5391 A_1 = E times C_1 times l E = A_1/C_1 times l = 0.5391/0.12 times 10^-3 mol cm^-3 times l(cm) = (0.004492/l(cm))mol cm^3 \r\n E times C-2 times l = A-2, A_2 = -log(0.442) = 0.3546 E = a_2/C_2 times l rightdoublearrow C_2 = A_2/E time l C-2 = 0.3546/0.004492 times l(cm)/l(cm) = 78.9354 mol/cm^-3 = 78.9354 mol/cm^3 C_2 = 78.9354/1000 mol L^-1 C_2 = 0.07893 molar (1)(a) Orange color leftrightarrow Blue green rightarrow (450 - 495) (b) Blue - green leftrightarrow Orange-red rightarrow (590 - 620) nm