What unit is commonly used for molar absorptivity (ε) in the Beer-Lambert Law?

Molar absorptivity, or molar extinction coefficient, is a crucial parameter in the Beer-Lambert Law, which relates the absorbance of a solution to its concentration and the path length of the light passing through it. The correct unit for molar absorptivity is expressed as dm³ mol⁻¹ cm⁻¹.

This unit breaks down as follows:

• "dm³" indicates that volume is measured in cubic decimeters, which is equivalent to liters.

• "mol⁻¹" signifies that the value is normalized per mole of solute, representing the concentration of the absorbing species.

• "cm⁻¹" reflects the path length through which the light travels, measured in centimeters.

When combining these components, the resulting unit allows you to quantify how much light is absorbed by a solution per mole of a substance at a specific path length, providing a clear relationship in analytical chemistry for determining concentrations based on absorbance measurements. This specificity is essential for accurate and consistent calculations in spectrophotometric analyses.