Question

Examine the given Beer's Law standard curve for an unknown dye measured in a 1.0 cm cuvette. What is the concentration (in M) of a sample of the unknown dye with an absorbance of 0.25 at 542 nm?

Answer 1

Without the standard curve or exact molar absorptivity for the unknown dye at 542 nm, you cannot calculate the concentration; typically, you would use the formula c = A / (ε * l) after obtaining ε from literature or experimental data.

Step-by-step explanation:

To calculate the concentration of an unknown dye using the Beer's Law standard curve, you begin with the measured absorbance of 0.25 at 542 nm. However, without the actual standard curve, we will assume Beer's Law is followed with a straight-line relationship between absorbance and concentration (A = ε * c * l). Given the molar absorptivity (ε), which is not provided but typically found in literature or experiments, we would use it along with the path length of the cuvette (l, which is 1.0 cm) to find the concentration (c) of the dye. The formula rearranged to solve for c is c = A / (ε * l). Using the molar absorptivity if it were given, you would simply plug in the numbers and solve for the concentration.

For example, if the molar absorptivity was 14,150 M¹cm¹, the calculation for the concentration would be:

c = 0.25 / (14,150 M¹cm¹ * 1 cm)

Performing the calculation would give you the concentration of the unknown dye in moles per liter (M).