Final answer:
Absorbance is a quantitative measure without units and is directly proportional to the concentration of the substance in solution. It is used alongside the extinction coefficient to calculate the concentration of a sample when the path length and Amax are known.
Step-by-step explanation:
Absorbance is a quantitative measure and has no units. It is directly proportional to the concentration of the substance in solution. If we divide the observed value of A at Amax by the concentration of the sample, we obtain the molar absorptivity, also known as the extinction coefficient (ε), which is characteristic of a given compound. Typically, sample holders are designed with a path length of 1 cm, contributing to the units for molar absorptivity being L*mol⁻¹*cm⁻¹. For instance, with a known molar absorptivity, if we measure the absorbance at this wavelength, we can calculate the concentration of our sample easily. Concentration is a quantitative measure of the relative amounts of solute and solvent present in a solution and can be expressed in various units such as mass/volume percent, mass/mass percent, or volume/volume percent.