4.8: Spectrophotometry

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Absorbance and Beer-Lambert Law

Exercise \(\PageIndex{1}\)

Which of the following is the correct representation for absorbance of a sample?

A = -log T
A = log (-T)
A = 10^T
A = 10^-T
A = 10^-1/T

Answer: a. A = -log T

Exercise \(\PageIndex{2}\)

Calibration of a spectrophotometer using a series of green dye containing solutions provides a set of data which follows the Beer-Lambert Law, with a trendline of y = 1.398 × 10³x (y-axis = absorbance, x-axis = molar concentration). What is the molar concentration of a solution with an absorbance of 0.8427?

Answer

\[y = 1.398*10^{3}x\]

\[x = \frac{y}{1.398*10^{3}}\]
\[x = \frac{0.8427}{1.398*10^{3}}=6.028*10^{-4}mol/mL=0.6028M\]

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