Question

The absorbance of a chlorophyll a standard solution in ethanol (density = 0.785 g/mL) is measured in
a 1.3 cm cuvette or path length. The absorbance is 0.765 and the molar absorptivity coefficient is 86,300 M–1cm–1.
The molecular weight for chlorophyll a is 893.49 g/mol.

What is the concentration of the solution in ppm?

Answer 1

A= ebc
0.765 = 86,300*1.3*c
Solve for c = approximately 7E-6 Molar = mols/L soln.
g = 7E-6*893.49 = about 0.006 g chlorophyll/L soln.
1000 x 0.785 = 785 g ethanol.
Concn = about 0.006g chlorophyll/785 g soln.
Change that to ppm. The easy way to do that is (0.006/785)*1E6 = ?
Check my work carefully.