A standard solution of 1.042*10^-4 M of palladium/phenylfluorone complex Pd(C_19

Question

A standard solution of 1.042*10^-4 M of palladium/phenylfluorone complex Pd(C_19H_12O_5)^2+) in a cell with pathlength 0.500 cm has a transmittance of 36.49% at 630 nm. Calculate the absorbance Molar absorptivity of the complex If an unknown solution has a transmittance of 17.53% in the same sample cell and at the same wavelength, find the concentration. An alloy of titanium and vanadium was analyzed to find the composition of each component. The alloy was oxidized to convert the components to the Ti^4+ and V^5+ states, respectively, and mixed with peroxide to form an absorbing complex. The absorbance of the mixture was noted at two wavelengths, as was the absorbance of two standard solutions, as tabulated below. All measurements were done in the same sample cell. Find the composition of the mixture. Each standard was 5.00*10^-4 M.

Explanation / Answer

3. For the given complex

a. absorbance = 2 - log(%T)

                        = 2 - log(36.49)

                        = 0.438

b. molar absroptivity = absorbance/path length x concentration

                                 = 0.438/0.5 x 1.047 x 10^-4

                                 = 8407 M-1.cm-1

c. Unknown

absorbance = 2 - log(17.53)

                    = 0.756

concentration = 0.756/8407 x 0.5

                      = 1.8 x 10^-4 M

4. molar absortivity for

Ti

at 406 nm = 0.360/5 x 10^-4 = 720

at 457 nm = 0.240/5 x 10^-4 = 480

V

at 406 nm = 0.106/5 x 10^-4 =212

at 457 nm = 0.137/5 x 10^-4 = 274

Mixture

0.722 = 720[Ti] + 480[Ti]

0.479 = 212[V] + 274[V]

So solving these two would give Ti and V concentrations

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