State the Beer-Lambert law and explain what each symbol represents.

State the Beer-Lambert law and explain what each symbol represents.

• A. A = ε b c; A is absorbance, ε is molar absorptivity, b is path length in cm, c is concentration in M.
• B. E = m c^2
• C. pV = nRT
• D. A = k l c

Answer: (A)

Light absorption in a solution scales with how much of the absorbing material the light passes through and how concentrated that material is. The Beer-Lambert law expresses this with A = ε b c. A is absorbance, a unitless measure of how much light is removed from the beam. ε is the molar absorptivity (extinction coefficient) for the species at the chosen wavelength, a constant that tells you how strongly the substance absorbs light per mole per centimeter. b is the path length—the distance the light travels through the solution in centimeters. c is the concentration in moles per liter. Because A depends linearly on both b and c for a given ε, the absorbance increases as either the path length or the concentration increases, which is why spectrophotometric measurements can be used to determine concentrations from a calibration curve. The other listed formulas describe different physical relationships and do not describe how absorbance varies with concentration and path length.

Light absorption in a solution scales with how much of the absorbing material the light passes through and how concentrated that material is. The Beer-Lambert law expresses this with A = ε b c. A is absorbance, a unitless measure of how much light is removed from the beam. ε is the molar absorptivity (extinction coefficient) for the species at the chosen wavelength, a constant that tells you how strongly the substance absorbs light per mole per centimeter. b is the path length—the distance the light travels through the solution in centimeters. c is the concentration in moles per liter. Because A depends linearly on both b and c for a given ε, the absorbance increases as either the path length or the concentration increases, which is why spectrophotometric measurements can be used to determine concentrations from a calibration curve. The other listed formulas describe different physical relationships and do not describe how absorbance varies with concentration and path length.