It is first day working at a large company called YahPoo bathroom cleaner chemic

Question

It is first day working at a large company called YahPoo bathroom cleaner chemical company. Your job is to inventory a series of very expensive solutions which the company makes. While doing so, you accidentally knock over two containers of RK1 and N719. You want to quickly clean up and dispose of the spilled solution, but you are unaware of the concentration of each in the spill. The molar absoptivity of N719 is on the solution label, but you have no information on RK1. Being the savvy spectroscopy student you are, you quicklymake a set of dilutions the RK1 stock and rrurn the samples on a Quick Run UV-Vis spectrometer. Unfortonutely, you cannot find any 1 cm pathlength cuvettes, so you settly with a 1.5 cm one. A sample spectrum and table of absorbances are shown below. You then run the spilled solution and find that the absorbance of the mixture has an absorbance of .998 at 475 nm and .685 at 550 nm. Find the concentration of RK1 and N719

Explanation / Answer

Plot abs vs conc. for RK1

slope of curve is the molar absorptivity x path length

So, molar absorptivity would be thus, slope/1.5,

at 475 nm = 1.949 M-1.cm-1

similarly at 550 nm = 200 M-1.cm-1

are molar absorptivity values

For mixture,

A = A1[RK1] + A2[N719]

let Cx and Cy be concentrations of RK1 and N719 in sample

at 475 nm

absorbance = 0.998

0.998 = 200[Cx] + 0.121 x 1.5[Cy]

0.998 = 200[Cx] + 0.1815[Cy]

at 550 nm

0.685 = 1.949[Cx] + 0.7905[Cy]

solving the equations,

[Cx] = 4.5 x 10^-3 M Is concentration of RK1 in sample

[Cy] = 0.86 M Is concentration of N719 in sample

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