The absorbance of a molecule, A, is proportional to its moNote that g/mL is equivalent to ppm;

The absorbance of a molecule, A, is proportional to its moNote that µg/mL is equivalent to ppm; this is a common unit in atomic absorption spectroscopy

(AAS) which is usually done at low concentrations.

lar absorptivity, , (with units of mL cm−1 µg

−1

), the path length of the cell,

b, (measured in cm), and its concentration,

c, (measured in µg mL−1

) using the equation A = bc.

a. What are the units of A? Why do you think A has the units it does. (Hint: look up the definition of absorbance).

b. In a solution with three known substances of unknown concentration (called c1, c2 and c3, respectively), the following measurements were obtained:

A1 = 0.2850 = 0.0010c1 + 0.0015c2 + 0.0010c3, A2 = 0.5000 = 0.0020c1 + 0.0020c2 + 0.0020c3, A3 = 0.5450 = 0.0020c1 + 0.0015c2 + 0.0030c3.

Construct a matrix equation to represent this linear system and use an appropriate software package to find the inverse matrix, thus solving the linear system to find the unknown concentrations, c1, c2, and c3.