Concept: Beer’s law is the linear relationship between absorbance and concentrat

Question

Concept: Beer’s law is the linear relationship between absorbance and concentration of an analyte. It is written as:

A = lC

Where: A = Absorbance of the analyte solution at max

= molar absorptivity (or molar extinction coefficient) of the analyte, L mol-1 cm-1

l = light path length of the cuvette containing the analyte solution, cm

C = concentration of the analyte solution, mol L-1

Based on Beer’s law, the absorbance of standard dye solutions at max (A) should be linearly dependent on the corresponding dye concentrations (C). In other words, if a calibration curve (standard curve) is made by plotting the absorbance of standard dye solutions at max against the corresponding dye concentrations, the calibration curve should be a linear line, and the slope of the calibration curve is l.

In accordance with Beer's Law, the slope of the linear trendline on a plot of absorbance versus concentration is equal to _______.

A. the light path length

B. the equilibrium constant

C. the transmittance

D. the molar extinction coefficient

E. the product of the molar extinction coefficient and the path length

Explanation / Answer

E the product of the molar extinction coefficient and the path length

Beer's law is expressed as Absorbance = e L c. To find the concentration for a solution that has an absorbance of 0.60, you will first need to find the slope of the BEST-FIT line. From the slope of the best-fit line together with the absorbance, you can now calculate the concentration for that solution (i.e. Concentration = Absorbance / Slope)

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