(25) Shown below is a Beer\'s law calibration graph obtained at the optimum wave

Question

(25) Shown below is a Beer's law calibration graph obtained at the optimum wavelength for a set of standard solution containing copper (II) sulfate. The linear regression equation for the best-fit line is labeled on the graph together with the R-squared value. Beer's Law Calibration Graph 0.500 y- 34.3x+0.0032 0400 R2 = 0.9982 0300 0.200 t 0.100 0 200 400 600 800 1000 12.00 1400 16.00 Standard Solutions Concentrations (M x10) -3 (a) Using the linear re constant (c) for copper (ID) sulfate. You may assume the path length of light equal to i.21cm (b) Using the Beer's Law absorbance limit discussed in lecture, what is the maximum standard concentration (in gression equation provided on the graph, calculate the experimental molar absorptivity M) of copper (Il) sulfate that can be used for Beer's law analysis based on the calibration graph?

Explanation / Answer

As shown in the pic, the equation of the calibration plot is:

y = 34.3*x + 0.0032

Here,

y = absorbance

x = conc in M*10-3

So,

Absorbance = 34.3*conc in M*10-3. + 0.0032

Ignoring the 0.0032 term, and comparing to the Beer Lambert's law:

Absorbance = e*l in cm*conc in M

So,

e*l = 34.3*10-3

Given that l = 1.21 cm, we have:

e = (34.3/1.21)*10-3 = 2.834*10-2 M-1cm-1

Hope this helps !

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